Selecting the right camshaft - Compression Myths How much compression can you run on pump gas?

[@edpetrocelli2633]

Hearing you talk about that GM "151" cam made me smile, It was my number 1 choice for my pump gas street engines in the early 70`s. In the early 90`s I used the 292H Comp cams for that lumpy idle the guys liked and it run strong in a 350. One of the old guys I worked with when I was a pup told me to assemble the long block on the stand put a starter on it and starting at straight up take a compression check then advance the cam and take another compresion check and stop when you got the highest reading, it worked surprizsngly well. Them old boys know there stuff.

[@goldsgarage8236]

Thanks for sharing your knowledge and experience Ed. That is a good method. AG

[@groomlake51]

I spent my whole life around drag racing and build blown fuel engines for a living. This is really really good content. Touching on things most enthusiasts don’t understand 🤘🏽

[@goldsgarage8236]

Thanks Groom. Nice compliment coming from someone with your credentials. AG

[@rogermunoz8134]

Mr. David vizard is great! There’s only like 4 guys that I know of that can explain it really well! My respects to all of you’

[@goldsgarage8236]

Nice compliment Roger. Thanks so much. AG

[@krusher74]

I wish one of them could not take 20 mins to say what should take 2 mins.

[@Steve69SS396]

I ran well over 13:1 on pump gas. I did not build this engine to run on pump gas. I purchased a used 406 short block and was going to put my top end on it which consisted of a set of AFR210's and a port matched Victor Jr. with a Race Demon 835. The 406 turned out to be junk and I already had a camshaft made for it for nitrous. The compression of this 357 smallblock was well over 13:1. The pistons were Ross 91461 with a 15.2cc dome, it was zero decked, the chamber size of the heads was 66cc and the head gasket was 0.040" thick. The cam was 268/274 @ 0.050" with a 108ICL, 112LSA and 630" lift. I ran it on the street and raced it on the track with nitrous. After running it for a while I did a cold compression check and it came in at 195-205. This was lower than my previous 355 so I ran it on 91 octane pump gas while on the street and race gas when I took it to the track. Race weight was 3,420 and it ran 11.20's at 120 on the motor and Ten teens at 132 on a 175 shot.

[@goldsgarage8236]

Thanks Steve for sharing your knowledge and experience. Confirmation for me. AG

[@steveb7310]

It never occurred to me that the cam would directly affect compression, but thinking about it it makes total sense. Many years ago (1985), I had a 1972 Oldsmobile with a 455 that appeared to be stock. It had plenty of torque and was fairly good on gas. I always ran Sunoco Ultra which at the time was 93 octane and it ran great on it. I did cranking compression test on it and got between 185 and 205 psi. It also had nice idle and the stock GA heads typical for ‘72 455s. Thanks for the great presentation, you got me thinking.

[@goldsgarage8236]

Thanks for the info Steve. We are always learning. Your compression pressure explains your good torque and mileage. AG

[@Shaft-Industries]

I remember reading an article in a Chevy Hi Performance magazine where some automotive school was tasked with trying to make 700 ft lbs of torque on 87 octane. They ALMOST succeeded except for a mechanical problem with a spiroloc missing. The build was a 502 BBC with hypereutectic pistons having a CR of 12.5:1 and the engine having a special flat tappet grind and including Feuling aluminum peanut port heads with small chambers. I believe they used a Holley street ram efi setup along with an aluminum radiator filled with Evans NPG coolant. The motor ran fine until the wrist pin on one cylinder worked its way into the side of the cylinder. I recall being amazed that such a high CR could be utilized on 87 octane. I wish these greedy petroleum companies would produce just one street octane of like 95 or thereabouts. Europe only does one octane to my understanding. Thanks for a great video.

[@goldsgarage8236]

Thanks Racer, that is a stretch for sure. AG

[@RickHaile]

In about 1992 I had a 68 Camaro daily driver with a .30 over 454. I had a .250 domed piston, with a Comp Cams 292 Magnum cam. 244 at 50 and .556 lift. The cranking compression was 225 lbs. on average! I used a stock converter, Turbo 400 trans., and a 4:10 12 bolt rear end. I drove the car on premium fuel at 91 octane. I had to dial back the timing to stop detonation. It wasn't an ideal combo for the street, but it was a beast! The widest tire you can run on a 68 Camaro is 11.5 inches. That's what I ran and the Hoosier Quik Time street tires couldn't hook! It was a ball to drive!

[@goldsgarage8236]

Thanks Rick. That would be a beast for sure. You were definitely pushing the limits of pump gas and also it makes me think i am being conservative with my 180PSI target for street engines. AG

[@RickHaile]

@@goldsgarage8236 Less compression and or more duration on the cam would have been better for a daily driver. The car ran a best of 12:31 at 114 m.p.h. at the track. My best 60 ft. time was a terrible 2:19, because of loss of traction! I never did run it on slicks. In 4 years of street racing I only lost 3 times, and all 3 cars were running either nitrous or blowers! I never lost on the motor only. I was the only true daily driver racing at the time. The Camaro was my only car.

[@jetkilr218]

I don’t think most consumers and average enthusiasts understand that dynamic compression is what matters and yet all you hear about is static. Great video!

[@goldsgarage8236]

Thank you very much Jet. AG

[@rogermunoz8134]

It is a Chevy engine, my respects; I’m mopar small block, but you explain it so simple I respect you, and every one no matter what brand!!! The knowledge you have some humans don’t understand that did not grow on roses over a few nights!!! Thank you so much for this serious and true information!!

[@goldsgarage8236]

Thanks again Roger. We will have a 340 Mopar on the stand as soon as I get these Pontiac's done. AG

[@ianbuilds7712]

Its bc all pushrod v8s are very similar... So things I say about an ls or sbc I can say about a Windsor mopar Pontiac Olds to a lesser extent hemis and semis

[@leosun8469]

Like yourself, I am a student of David Vizard. I believe you are spot on with everything that you have stated. I’m currently building a 400 sbc for a ‘70 Camaro using a lot of David Vizard’s principles. I thoroughly enjoy your videos, so keep them coming please! Thanks for all your efforts.👍🏻

[@goldsgarage8236]

Thank you Leo. I will also be building a 406 for my son's circle track car soon. Watch for it. AG

[@troyberg65]

Aiming for the 160 psi cranking compression mark compared to the 180-200 mark depends on a lot of factors. Having extra leeway for detonation resistance is a good thing but it trades off a bit of power. The person that might not have the knowledge to monitor that they might be more prone to engine damage in certain circumstances (like a particularly hot day), should probably have a bit more leeway for their car. The vehicle it's going in plays a roll too; lighter cars with shorter gears are going to be less prone to detonation too. Then there's also the little things in the build; like smoothing out edges in the combustion chamber, quench, piston style etc. All great information. Great video

[@goldsgarage8236]

Thank Troy, the problem I have with building engines for others is that i have no control over these things once it is off the dyno. i worry about them all. Thanks for your input. AG

[@carloshendrix5685]

@@goldsgarage8236can 93 be ran in a 12:9:1 compression 408

[@thereluctantgearhead4544]

The late, great Joe Sherman once said if it pumps under 200psi, it'll run on pump gas. I've ran 13-1 engines on 93 octane on the street, of course I used racing fuel at the track.

[@racerd9669]

You are talking about that cheating bastard, he was great at that for sure.

[@goldsgarage8236]

Thanks for the info.

[@thereluctantgearhead4544]

A man could learn alot from Joe Sherman. Shame he passed away.

[@ToddWright2]

Sport bikes commonly run 13+:1 on 93. Of course they have 3D air and fuel tables and huge development budgets.

[@trailerparkcryptoking5213]

What changes did you make to your tune to switch between fuels?

[@johnhughes2043]

I’ve watched a few of your videos and I like your approach to things. I don’t always agree, BUT, at the end game I understand your position. When you dropped the David Vizard bomb, I was like …. ok… we’re on the same plane and path! I’ve been a Smokey Yunick guy from the mid sixties on. I would bet most us from that time, that he had an influence on us, regardless of the brand. Really like the channel, well done.

[@deancrawford2577]

Thank you for explaining that so easily and precisely. As an Automotive machinist, I have tried many different engine combinations with compression ratios, from using frquencied inlet manifolds to boost low and midrange torque, to camshaft s with various duration and split etc etc. Yes you can run 12:1 + on pump gas and still have a great performance with the benefit of great fuel mileage to boot.

[@goldsgarage8236]

good points, thanks for your comment Dean. AG

[@danielllewellyn5720]

Thanks for throwing this information together in such a concise video. I've always known a cam, or cams have direct influence on dynamic compression, but the point you brought up about how quickly the cam acts vs the duration is interesting. I like how you broke it to a ratio. Simple. Subscribed.

[@goldsgarage8236]

Thanks for commenting and subscribing Danielle. AG

[@danielllewellyn5720]

@@goldsgarage8236 You are welcome. Just for the record I identify as a man and my name is Daniel.

[@krisjones1286]

I ended up getting 9 years out of a comp extreme 4x4 cam and Rotella oil. I used the truck for daily driver and off road adventures. At the 9 year mark it started chewing up a lobe on #4 and I had to sell the truck as I had no $ to fix and it was no longer practical for me. Thanks for the no flare no bs info, when you said thats fine we don't have to agree you got me.

[@goldsgarage8236]

Thanks Kris, good info and very nice compliment, appreciate it! AG

[@HeadFlowInc]

The old GM solid lifter cams had the valve timing and overlap to manage DCR. By closing the intake valve later it allows the SCR ie 11.00-1+ to bleed off cylinder pressure at low-mid rpm when the engine is more susceptible to detonation. Intake valve closing event is a huge factor in engines running 12.00-1 on pump “Premium” by lowering the DCR. Aluminum heads, rule on max DCR for 93 octane is 8.70-1… but many push it to the edge at 9.00-1 but be warned.😉 Iron Heads the max DCR for 93 octane has to be below 8.70-1, I haven’t found any data to share but I’d think less than 8.50-1 DCR

[@donwalsh7521]

Well said. Sir

[@goldsgarage8236]

Thanks Headflowinc. I am planning a follow up video on this subject. Thanks for reminding me to include the issue that engines are more vulnerable to detonation at low speeds. I have researched info in this subject.

[@jamesgravel7755]

Makes sense. I’ve never looked at it like that so it’s a new concept of thinking. I’m always building drag engines with no vacuum and making all the power up top.

[@goldsgarage8236]

Thanks James, If you are racing, that is what you need. I am going to discuss this further in my next video. Thanks for watching. AG

[@edsmachine93]

I agree 180 compression minimum. I target between 185 to 200. But that's not written in stone. All kinds of factors, cast iron heads, aluminum heads. Cast heads static lower. Duration @.050, gears, tire size. And finally, the customers ability to tune the combination. Conservative is good always. But pushing the envelope requires knowledge and experience, not guessing. And I have not even got into carburetors and Fuel Injection. Pump gas, compression up, timing back. Like I said, not written in stone. And a learning curve, always. Great topic. Thanks for sharing. Take care, Ed.

[@goldsgarage8236]

That is correct Ed. I will have more about that in my next video. Please keep watching.

[@Walkercolt1]

My 1998cc Alfa Romeo Spyder (mechanical direct injected) is running 16.5:1 corrected CR on unleaded premium (92 octane 100% gasoline) pump swill and has been for 41 years. It is a Hemi head and it turns 16,000 RPM (peak HP at 12,600 RPM) , but Alfa was building engines that turned 10,000 RPM RELIABLY before WWI! BTW, the Alfa engine has NO valve springs-it uses desdemonic valves with followers (forks) that push open and pull the valves closed. It also has a Magneto Marelli magneto and surface electrode spark plugs that whines like a turbo, driven by the crankshaft. The clock is showing 180,000 Km and it doesn't use any more oil than when new (about a liter between changes, normal by the owner's manual). The four-banger holds 7 liters of oil WITHOUT filter or nearly 9 with filter (big oil cooler built-in).

[@goldsgarage8236]

Very cool Ricky, must sound great at 16,000RPM. Different world than Detroit muscle.

[@davidreed6070]

Cool very interesting. I'd like to see the valve train

[@kevinkelley3657]

Big American engines with long strokes cannot reliably turn over about 6000 rpms in somewhat stock configuration. I have no idea what affect extremely high engins revs have on pre-ignition. Most stock engines sold in North America are around 89mm stroke. A $40,000 full custom race engine for circle track use will usually be 6.7 to 7.6 liters, roughly, and they are usually around 100mm in stroke. These engines will run several thousand laps in a year, and they will have acceptable reliability at around 9000 rpm maximum rotation speed.

[@Wardaddy1124]

​​​@@kevinkelley3657 i have a 427 that I run it at 8500 rpms it's a aftermarket Dart aluminum block and 12/1 compression I run M1 methanol and a 98mm forced Inductions turbo point being you can build à reliable engine to turn rpm mine is a small block but that's all that I will give out Openly on here I still race so I'm just saying you can you just have to get the right parts and engine builders I go to tkm there the best in the country.

[@kevinkelley3657]

@@Wardaddy1124 I said in my comment that "custom engines" could turn 9000 rpms reliably in a circle track engine, for one year...........I said that these engines were usually around 100mm in stroke. If you disagree with me, what is your exact argument? I have a VERY good friend who is THE machinist to use in this are........I also understand what aftermarket heads are capable of doing. I am not sure that I understand your argument, but if you have $10k to 15K to spend in parts, you can absolutey build a 9000 rpm chevy based engine that should live for 40 races on a round track under 1/2 mile in length.

[@slowcountryboy476]

I was loking at the comments and failed to see anything negative or disrespectful so my respects to everyone who chimed in. I totally understood everything you spoke on; however, I am going listen again another time or two. My theory is akin to reading a book, one learns stuff that was missed during the first read, or perhaps something becomes more clear. Thank you for making this video. By the way, the GM Duntov or 30-30 cam was my favorite cam. I would set the lash at 26-28 for more low end torque.

[@goldsgarage8236]

Thanks you for the nice comments. AG

[@carclubriot]

Thank you for all the information you put out sir, I always learn something new every time 🙏🏼

[@goldsgarage8236]

Thanks Gabe, you are motivating me to keep digging. Watch for more coming soon! AG

[@corvettefever360]

I respect what he just said about David Vizard. And that's the way it should be, he sees a lot of points and recognize that David knows a lot of stuff, however we all have different ways We've Come To What We do. I've been building high performance engines for over 20 years and I still learn and listen to different people. And just because I don't exactly agree doesn't mean they are necessarily wrong. We're too busy trying to show up each other and sound like we all know what we're talking about and are complete experts that we're not open to other opinions. Sometimes two people can have different ways to get to the same end result. And to become better at our craft the things we all love to is having our ears open and listening to others who also know what they're doing. You'll learn and take the best of each thing and then with actual application of your own you learn yourself what works the best for you

[@goldsgarage8236]

All good points, thanks for your comments Corvette. AG

[@bobbyoshomebuilt2544]

Answer to your final question, while I'm only guessing, I'd say low speed and load maybe, depending on many variables. But as RPM increases the addition cylinder filling would send cylinder pressures way beyond what 87 could resist. I built an 11.6 to 1 408 small block with cranking pressure of 217. It's a tight quench motor with aluminum heads. While it runs very well on the primaries, 93 octane (tunnel ram) it does rattle @ W.O.T unless I use race gas. I think it's because of the same reasons stated above. Backing timing low does not help. My W.O.T AFR is fat as well @11 to 1 so i don't think it's a lean induced rattle. Although I can not rule out poor cylinder to cylinder AFR. Love the tech by the way. I'm always looking to learn more, thanks.

[@goldsgarage8236]

Thanks Bobby, you are braver than me but it sounds like a very nice engine. I am planning to address the points you mentioned on a follow up video so thanks for the input. AG

[@bobbyoshomebuilt2544]

@@goldsgarage8236 Looking forward to it!

[@DuneWest]

If did the calculations correctly (as you say at the end of your video) then, my Comp Cams "Low Shock" cams on the cam card are showing an Advertised duration of 276*/282* and 246*/252* shows 1.12 for the Intake and 1.11 for the Exhaust and according to what is being explained in this video it sounds like my cams have very aggressive ramp speeds which I told them I DID NOT WANT---I specifically told the tech from Comp Cams that I wanted their "Low Shock" cam profile design with easy, smooth, non-aggressive ramps. I guess they didn't get the memo!!! I will send them back! Thank you for your video and detailed explanation.

[@goldsgarage8236]

Thanks Dune, glad you found the information helpful. AG

[@DURRIESVISION]

Always look forward to listening to your channel.... 'down under Oz' 🇦🇺

[@goldsgarage8236]

Thanks RJD, thanks for tuning in and look for more on the subject. Allan Gold

[@Gunnypauly73]

My 2018 F150 with the 5.0L has 12:1 . It can be run on 87, but I run 93., previous owner of 67 GTA fairlane 390, 70 cougar, 351W & 79 Mercury Capri with 351W with 289 heads ... Did Not like anything less than 101 octane. Ultimately the engine died from pre-ignition. Great video Sir.

[@goldsgarage8236]

Thank you Gunny for your comment and sharing your experience. AG

[@icsamerica]

Combustion chamber shape has large impact. One extreme example is the Jag HE V12 engine, has a pocket in the combustion chamber that's 11.5 to 1 on pump gas back in the 80's. Also today's modern heart shaped tight quench wedge shaped chambers are more resistant to detonation. Also good spark control off the crank shaft helps. This is a particular problem on the SBC with it's dist far back and at the end of the cam... that make the spark bounce around, that's no good and that variation can cause erratic spark and trigger detonation. Crank triggers are a must with high compression.

[@goldsgarage8236]

Thanks for the comment John. You have deep knowledge on this subject and giving us something else to think about. AG

[@smarternu]

I struggle with small block mopars trying to make them run smooth. I put on a set of "fast burn" heads, heart shaped modern design and Wow, what a change. Best small block Mopar I have ever seen.

[@wildrosegarage4208]

Great video. I run a w30 4spd cam in one of my 455s and it has 329 duration they are lazy cams compared to todays grinds because of the ramps. But are easy on valve train.

[@goldsgarage8236]

Thanks for sharing Wildrose.

[@SpecialAgentJamesAki]

I have a fast ramp cam and heavy springs in my olds 455 and it beats the tar out of the valvetrain especially those ridiculously long pushrods are definitely bowing.

[@Jeffsa12]

Just as dynamic compression, set by the camshaft events greatly influences cranking cyl pressure, a running engine has variables that determining the octane requirements. A high compression race engine with over 14:1 calculated compression ratio with a relatively short duration cam could reliably run on 87 octane gas no problem, if the torque load was kept minimal. This would require a throttle opening to maintain relatively high intake vacuum. In this case, the engine can't develop high combustion pressures/temps associated with detonation. There's a ton of other factors at play, combustion chamber temp and efficiency, total ign. timing requirements, accuracy of maintaining proper fuel distribution and ratio evenly across all engine loads and cyl to cyl, etc... Short answer, in an old school carbureted muscle car era engine, I would agree with your assessment on taking a close look at cranking compression pressure as a good overall indicator of detonation resistance. Unless someone was willing to spend a ton of money to modernize all the development shortcomings due to age of these old engines, and taking the owners dedication and ability to monitor for signs of detonation, I'd say anything over 10:1 would really be pushing it when combined with a typical hot-rod street camshaft.

[@goldsgarage8236]

Thanks for the input Jeff. AG Look for future videos on this subject.

[@ehb403]

OEMs (and those of us working on emissions reductions in hot rods) have other tools as well. The decrease in fuel mileage you mentioned can be combated with variable valve timing, EGR, and even Atkinson-Miller via valve timing. The tough part (which is what I’m working on) is variable duration as well, in order to maximize power when using race gas. There are other tools I’m also working on, but these are proprietary (my goals for my 4.6 liter Ford Mustang are 450 hp / 45 mpg on pump gas - not at the same time of course).

[@goldsgarage8236]

Thanks Ed. those are all good technologies. Let us know how your Mustang build goes. AG

[@johngregory4801]

2, 3 or 4 valve heads?

[@ehb403]

@@johngregory4801 3 valve. I chose 3 valve because I’m removing the camshaft (and all the junk in the middle related to the lash adjusters) and replacing it with a pneumatic valve actuating system. 3 valves gives about the same performance as 4 but requires less compressed air for the pneumatic system. The pneumatic actuators are electronically controlled so i have COMPLETE freedom of valve timing specs.

[@johngregory4801]

@@ehb403 COOL! Who's it from? I've seen pneumatic valve spring systems before, but not pneumatic actuation for valves. Talk about being able to optimize timing for all revs and all conditions!

[@ehb403]

@@goldsgarage8236 The engine is from a Mustang, but it’s going in my Ford Fusion…mainly because my wife nixed putting it in the Lincoln MKZ (same car with nicer options and accessories) since it already has a 400 HP engine in it from the factory.

[@jonathanborden1424]

Eric Weingartner's Videos on camshafts and cylinder heads is pretty informative.

[@goldsgarage8236]

Thanks for the tip Jonathon. I watch Eric also. AG

[@pockets5628]

My 467 has 10:1 static compression, and 200psi cranking compression. It runs on 91 octane with 36 degrees of timing locked out. No pinging ever. Also, I recently tested Shell 93 octane. It had 7% ethanol. And I also contacted Shell Canada about ethanol content in their 91 and 93 octane fuel. They replied just today that their 91 and 93 now contain up to 10% ethanol.

[@goldsgarage8236]

That is good information Pockets, Here, there was a sticker on pump saying that 91 contains no ethanol. I will check again. Thanks for the comment, please keep watching. AG

[@gregk.6723]

Try E-85, wow !

[@MrLuvtheUSA]

I have a 302(5.0 coyote) with 12.5:1 compression and about 180 psi cranking pressure which I run on 91/93 235/237 duration ~535 crank HP

[@Daveunruh]

Well then your fuel mixture is below 12.8. There’s got to be a trade off somewhere.

[@BB-fv2dw]

Definitely good content I have that dilemma now with a 400

[@goldsgarage8236]

Thanks for watching and commenting BB. AG

[@hankclingingsmith8707]

VERY WELL PRESENTED. ALSO LOBE SEPERATION ANGLE. L88 WAS 114. TIGHTER LIKE MOST COMP CAM STREET CAMS ON 110 MAKE MORE CYLNDER PRESSURE WHICH EQUEALS MORE POWER. ALUMINUM HEADS ALOW 1 POINT MORE COMPRESSION ON SAME OCTANE..180 TO 200 PSI ON A PERFORMANCE STREET MOTOR RUNS NICE. BUT NOT SO MUCH FOR TOWING BECAUSE OF HEAT GENERATED LONG TERM

[@goldsgarage8236]

All good points Hank, thanks for contributing. I will be making more videos on this subject, watch for it.

[@jamesm2464]

Direct injection is the key to running on pump gas with high CR. My 2023 F-150’s 5.0L V8 engine is running a 12:1 compression from the factory and can run 87 octane up through E-85. On 91 octane the crank ratings are 400 HP/410 LB FT from the factory. On E-85 it’s 420 HP/430 LB FT (also from showroom floor). It actually uses dual PFDI injection (One DI and one PI injector per cylinder.

[@goldsgarage8236]

Thanks for taking time to share your comment James. AG

[@ChrisJones-el7bw]

Having quench rather than open heads has huge impact on how much compression you can run. In Australia our standard 430hp 351c, which I still have in an XE ESP runs flat tops, 302c heads opened up to 66cc’s, F246 cam, Weiand excelerator, 750dp, good extractors straight thru mufflers which make 430hp at 200psi dynamic compression. No pinging but low gears and light car has a big impact on how much compression you can get away with using pump fuel.

[@ChrisJones-el7bw]

Forgot to add it’s a long rod 351c, which also lowers dynamic compression, uses a 302c 6” rod rather than 351c 5.78” rod, has modified pistons.

[@goldsgarage8236]

Hello Chris from Australia. Those are good numbers for a 351 and 200psi. What octane fuel are you using? AG

[@ChrisJones-el7bw]

@ Hi, The highest we have which used to be 100octane but now can only get 98, but equals around 94/5 in USA. I have 3.5 diff gears weigh around 1750kgs and top loader box.

[@rjordansr65]

I think You should be able to run off of 87 with this compression ratio! Here are the reason why: 1. Rod ration is a factor; the higher the better; 2. Combustion chamber design/efficiency; 3. Piston design/quench; 4. Constant cooling temp and adequate cooling system/components; 5. Good fuel quality/low ethanol content/low moisture; 6. Precision fuel metering/A F Ratio; 7. Vehicle weight; 8. Gearing and Transmission; 9. Appropriate Cam selection/Timing; 10. Properly machined and set-up Cast Iron head; 11. Correct Aluminum intake manifold! I also think a good oil and standard volume oil pump would be the right choice for a street application. 12. Properly sized exhaust system should complete the total package..

[@goldsgarage8236]

Thanks rjordanar, lots of thought, thanks for your input. I am planning a follow up video to address this soon. Please keep watching. AG

[@lambsweet]

Years ago I rebuilt an LT1 in my 70 Z28, although at the time I was led down a path of lowering the CR, I think stock was 11 or 11.5:1. When we were done I think I was around 9.5:1 and at the same time the GM performance handbook on LT1's listed a offroad cam for the engine, at the time Crane built one to that spec so I installed it. The engine never ran right so I called Crane and the first question "what CR are you running?" He said you need a minimum of 11.5:1 to run it. So I had to pull out that cam and replace it with a lower duration hydraulic. Now for my question; I am about to embark on a Ford 351w build with a brand new 4 bolt block. I am also making it a stroker 408ci. I do not want the high HP but I prefer a high torque motor, it's going in my '85 Jeep CJ7. Two things I would like to know; If I run E85 or 91/2 octane what CR should I shoot for? Also what off the shelf roller cam should I pick? Thanks in advance!

[@goldsgarage8236]

Thanks for the question Dave. With a roller cam, you need less duration, but you have lots of stroke so duration in the range of 210-220 degrees @.050". With 91 octane fuel, 10:1 CR with cast iron heads and 10.5: with aluminum heads. Design for a max cranking compression of 175-180psi. you can find on line calculators for static and dynamic CR and cranking pressure. I don't have any experience with E85 but I think you could run higher CR and cranking PSI. Hope this helps. AG

[@dondorfman3951]

What is not considered is why the intake closing is delayed. CCP does not consider actual running engine at higher engine speeds. The late closing allows inertial to better fill the cylinders so even though the engine degrees of duration with a closed valve is reduced on compression the cylinder has packed in a larger mode dense charge. The bleed off that is seen at low speeds and cranking is now negated. Dynamic cylinder fill takes over and the demand for higher octane prevails.

[@goldsgarage8236]

Very good point Don and so high speed detonation may occur. The difference is that at high RPM, detonation doesn't have as much time to do damage. AG

[@The340king]

The issue with cranking compression is the rpm the engine cranks at. Street engines with higher tension rings tend to turn over slower than a comparable engine with low drag rings. Higher compression can cause a slower cranking RPM if the plugs are left in the other cylinders. I typically remove all the plugs. This gives a better picture of the condition on the cylinder being tested. Sizing cams is an art. Bore to stroke ratio does come into play and it's opposite of what I thought it would be. The longer stroke engines appear to be more fickle with duration than shorter stroke engines. This is for racing applications and may not matter for street applications.

[@goldsgarage8236]

Those are all good points Brad. It is good practice to remove all the plugs and have good cranking speed when taking a compression test. Thanks for your input. AG

[@corvettefever360]

12.5:1 SCR on pump gas? Absolutely! Even with steel rims. Yep! Seen it done many times actually. Definitely premium gas, 93 octane from my experience. Can't comment about anything lower, but I have heard it can. I remember a time I believed in some of the stereotypes, and at the time they seemed correct because it typically came from people who seem to know what they were talking about, however I kept going back to the first time I seen very high compression with steel heads on pump gas. And that would be the engine my stepfather built. He was running 12.5 to 1 static compression ratio, Steelheads and ran 93 in it. No problems. Regardless this is when I was first starting out and learning everything. Buy my mid-teens my brother and I were already doing engine swaps in manual transmission conversions etc etc, and we were building what was considered high performance engines at the time, in the early 90s 400 or 500 horsepower was extreme horsepower, lol! Anyways what has seen my stepfather and others do always nagged at me when I heard the so-called experts on compression Now many many years later, when forced induction is in its prime, I continue to hear misconceptions about compression. People have this idea that when you use the force induction you have to go with extremely low compression which is not accurate. I am running 11.0:1 SCR with twin turbos. My brother 10.5:1 with a turbo. On premium pump gas. Don't get me wrong, we have Holley EFI systems which help with tuning and getting the best out of everything, however really is more based on putting the correct components together. Too many people look at the individual parts and or maybe a couple of them together. For instance you may look at the camshaft with cylinder heads or something like that when in fact it is everything all together and even as this guy has stated which is very important, is the intended use. Many people don't consider the load, factors that play such a big role in what you are doing

[@goldsgarage8236]

Good comments, you have given this subject a lot of thought. Thanks Corvette. AG

[@ae43ro]

I worked at a Chevy dealer in the 1960s, I did alot of tune ups, and we always performed a compression test. most cars fell into that 150 psi range. I worked on alot of Corvettes and some of the HP engines would push the psi well over 200 some as high as 250

[@goldsgarage8236]

Very interesting Monty. In the 1968 GM manual specifications, the highest cranking pressure for any engine is 160PSI, except the Z28 is 190PSI. Do you think carbon build up could be a factor?, or where these engines modified? Thanks for your comment, we are learning from your experience. AG

[@williamanderson4706]

Makes sense I love learning new things about engines and the why and how. Thanks for the info.

[@goldsgarage8236]

Thanks very much William, glad you enjoyed it. The response has prompted me to make a follow up so please watch for it. Thanks for watching Gold's Garage AG

[@duanedahl8856]

Well, it's quite possible it could. I'm at 3500 ft elevation, so a hot street engine in most cases needed 11.5 static compression and depending on the cams intake closing, it could definitely run great on pump. Good cylinder head chambers, and proper quench are also important. It's also worth mentioning that today's Ethanol blended fuels have a different Stoic ratio, it's not 14.7 to 1, it's 14.01 to 1, so a proper tune will need to be richer that most people think. And it won't require alot of timing because the fuel burns quicker. If you tune a high compression engine as If it was forced induction, it will be fine....

[@goldsgarage8236]

Thanks for the info Duane. We are 753 feet above sea level so that s not an issue here. Thanks for the info about stoic ratio. We tune for results on the dyno, usually about 13:1

[@steveamnmn]

@duanedahl8856 point is correct regarding the difference in air/fuel mixtures between straight gas and gasohol. Inherently today's engines don't make any less power on modern, alcohol-blended fuels versus gasoline from the "old days"; they just burn more of the new stuff to do it. In fact, modern fuels with higher alcohol content can actually help to enable greater power because the charge cooling affect of the alcohol permits more dynamic compression and/or timing (i.e., higher cylinder pressures without detonation).

[@100pyatt]

FYI the Mercedes M276 DE35 is a factory 12.2:1 compression ratio. I run mine on E15-88 , pump gas is no problem with high compression if the motor is built correctly to reduce hot spots in the combustion chamber that can trigger pre-ignition/detonation

[@goldsgarage8236]

Thanks for the info 100. AG

[@jacquelinechellis4036]

On a 350 Cid truck engine with 422 442 cam 204 214 at 050 dur. 112 lsa. Would a 194 intake valve size be a better choice for velocity and low speed torque. I want to buy some Brodix 180 heads but maybe that's a little too big and I want good mpg. Flat tops .020 down. Quadrojet with factory aluminum manifold.

[@goldsgarage8236]

Thanks for your question Jacqueline. I don't think the Brodix heads will hurt, but they are more than you need to work with the rest of your parts. If cost isn't an issue you could use them but there are less expensive heads that will work well. Hope this helps. Good luck with your build. AG

[@heshtesh]

I have to chuckle, watched my first video of yours and asked a question to then refresh my computer to land on my second video of yours that looks like its going to answer my question lol.

[@goldsgarage8236]

Thanks heshtesh. Glad you found what you were looking for. AG

[@michaelgpreuss8695]

Thank you for your wisdom....I've watch David Vizard and many others...I want to switch to BBC after a life time of being a 327 fan. I appreciate the fact that you guys are willing to share your knowledge...my next project is a 1968 El Camino with 4 speed 373 gears and red line of 6,000 RPM. This is a street car that i want to be strong as i can get with a 454 bored to 60 over or maybe a 496 stroker with iron heads....any advise would be greatly appreciated. Keep up the good work.

[@goldsgarage8236]

Thanks Michael. I recently built a 427 that is very similar to the ZZ427 GM Crate motor. There are videos about it and another one that I built on my channel. I will be installing this engine in a 1966 El Camino in two weeks or so. I will be making videos about the conversion from a SM. Watch for it.

[@jimmywilkinson9190]

Hal's dad gave him a 67 SS El Camino with a 396 4 speed GM 21 muncie . It was black and was amazing . the boboso traded it for a 1969 Triump 650 motorcycle . We all told him he f up .

[@jakal104]

​@@jimmywilkinson9190 IDK... if it was a clean Bonneville, I'd take it over the El Co. Big money for old Triumphs. J.S.

[@bigblockmaro1]

We ran our 482 big block Chevrolet with 12.5:1 on 91, for YEARS in a boat. Kept the timing at about 36 never had an issue. My current engine with 11.8:1 runs great on 91 with 34 degrees, been in the car since 2008 with EFI controlling the fuel.

[@goldsgarage8236]

Good reference info bigblock. EFI will help for sure. Thanks for sharing. AG

[@cammontreuil7509]

What temperature engine ran in boat ?

[@SVtuned]

good info probably should also mention how cams with large overlap will effect cranking compression. Mine makes only around 90 psi cranking pressure but has a large overlap and duration. Effectively pushing combustion out intake port at low speed. The compression ratios is around 9.5:1 engine is turbo charged and makes 700 hp from 2.4 liters at 8500 rpm.

[@goldsgarage8236]

Thanks for your input, onefasthatch, That is a big cam! I am going to discuss this further on my next video, I hope you watch for it. AG

[@chevybelair9230]

Overlap effects idle quality. Intake closing effects cranking pressure. More overlap will actually increase low to midrange cylinder filling and that is why dirt track guys run a 107 or 106 lsa cam instead of 110 or 112. The 106 - 107 will pull a lot harder off the corners but the idle quality will be horrible. If you are pulling up past 7k rpm the higher lsa 110-112 would probably be better because of better higher rpm cylinder filling.

[@olallaeddy]

I sent my cam in to a custom grind shop. Im building a stock FE 428 stock dish 4.13 pistons. After I got the cam back he said to keep compression lower than 9 to 1 and use a stall 2500 converter. Putting it in my 72 f250. Just now learning about cams. Just got my new pistons. Im seeing on my cam info card that intake V Closes at 38 ABDC. I need to assemble the rods n pistons to see what comp height is this week. I think the cam he sent me would raise the compression up if i understand correctly. My heads are 72 cc and gasket .o42. This is my first home built short block.

[@goldsgarage8236]

Thanks Ed, looks like that cam IVC is a good match for 9:1 CR. After you determine the deck height, you will have enough info to calculate the dynamic compression and cranking pressure. The Wallace racing on line calculator works pretty well. Good luck and let us know how it turns out. AG

[@olallaeddy]

Thank You. Oregon Cam here in Washington has been building cams for ever. After I do some measuring I will send him another core. I have quite a few here.

[@sepg5084]

12.5:1 on pump gas, is doable depending on what ignition timing one is running, depending on altitude, and how hot and humid the place is. Also how hard you're running the motor.

[@goldsgarage8236]

Thanks Sep. That is all true and I plan to cover this issue on my next video on this subject. Please watch for it. AG

[@alexvendrig9205]

congrats on subscribers passing 1k

[@goldsgarage8236]

Thanks Alex, missed you at hockey today!

[@hansanderson6607]

I once ran a 327 sbc with 10.5:1 compression with ported camel back heads, a pretty hot cam, headers, a Holley 600 (tuned) with a Mallory Unilite ignition. Ran very well for several years on 91 octane gas (NO pinging). Good aluminum heads might be better for more compression. I was probably putting out around 375-400 hp. Only reason I was "slow" was because I had a 3.42 open rear end in a 1972 Camaro. If I had a 3:73 posi, I would have been MUCH faster, especially with really good tires.

[@goldsgarage8236]

Thanks Hans. Gearing helps. I installed a 4.88:1 gear in my Camaro in 1969 and it was still there when i bought it back. Lot's of fun on the street. Sounds like you built a nice SBC. AG

[@waynecera4422]

great video, the thing that NO one ever talks about is how many BUMPS on the comp gauge is required to get the needle to 150PSI? Hydraulic lifters give mushy valve action when cold so thats why we test at operation temps. Ive done 100s of comp tests at GM on thier dynos in australia and the SLOWEST comp needle movement was from the LS series of engines, they required 8 comp bumps to get to the desired 150PSI with a 10.4:1 engine! But when we took out the corvette cam & installed a 5.3 truck cam the comp was now 165psi & it only took 4 bumps on the gauge! testing on the truck cam bought peak torque and horsepower down the RPM line about 1000rpm. My boat has a 351c with 302c heads & laid back chambers to give a measured 10.2:1 comp, with a 218 cam. comp gauge reads 165psi in 2 bumps on the gauge and it just likes 95 ron fuel ( your equivelent 91 octane)... I really enjoyed your video, keep up the good work.

[@goldsgarage8236]

Thanks Wayne from Australia. Did you know, the number 1 city in terms of clicks on my site is Milbourn Australia and many other cities in Australia are right up there so thank you for the great support. I think the Wallace Racing guideline is 7 bumps but for the reasons you mentioned I think you should keep going until the pressure reading stops going up. Usually that is about 4 bumps. 91 fuel should handle 165psi easily. Hope this helps. AG

[@cammontreuil7509]

What kind of exhaust manifolds on the cleveland in the boat ?

[@waynecera4422]

you mean MELBOURNE. Thats where im from. We have some smart people in the aftermarket head and manifold design. CHI heads ,AUSSIESPEED manifolds YELLATERRA heads& valve train SCOTT COOK cleveland heads , to name just a few.@@goldsgarage8236

[@tomstrum6259]

Thx for putting up such Rare & Helpful info on a very hot topic for us hp factory iron guys....It really Is a comparison & engine Octane fueling Dilemma because the popular 0.050" lifter spec cams & the typical solid lifter 0.020" cam card timing data Is Way Different from the factory 0.006" lift SAE valve timing specs......Even using Long ramp Bleedoff cam timing, Chevy Did affix Octane Warning stickers to factory Iron head, L88 engine that Minimum rated Octane was Ron 103 & Mon 95, with Mon rated fuel Preferred.....Why would Chevy bother with that warning If Lower Octane Was Not a Problem ?? ....Looks like Chevy Didn't put much faith in the DCR effect ??.....With U.S. Pump gas 92 AKI (R+M)/2 rated at 88 MON, how is that supposed to work with factory Stock shim head gasket & Internals ?? ......Around engine Max Torque Rpm range, the cylinder Does fill Beyond the IVC point, nearly to Full BDC cylinder capacity & Nullifies the Lower calculated Dynamic CR is Probably why.....Maybe the clever use of "Squish" optimized Aluminium heads & smart ECU Detonation sensor designed ignition system can let the Stock engines run flat out Again on the current pump gas Octane problem.......

[@goldsgarage8236]

Lots of info, thanks for sharing Tom. AG

[@kurthammack9867]

Thanks, I have a goat 🐐 that I have driven most of My life, and by luck, used a cam that worked well for pump gas, but now I know why, thanks!😊

[@goldsgarage8236]

Thanks for the comment Kurt. AG

[@jeffmckc2081]

We run over 16 to 1 on Pump Gas with Cranking comp of 220 we also don't go near Peak TQ or load it going down the road and chance to Race gas at the tracks. There is lot of work goes into being able to do this but it can be done.

[@goldsgarage8236]

Thanks Jeff, I don't even know how you would get 16:1? AG

[@jeffmckc2081]

@@goldsgarage8236 it’s a 712 inch all billet semi Hemi from Todd Goodwin it makes over 1300 hp. We Run Sick Week and Hot Rods Drsg Week. N/A it’s going 7.71 at 174 1.11 60 ft. Not to many people understand pumping losses from lift and duration, ramp design effects on it. Good information overall

[@edsmachine93]

I re-subscribed. I had already subscribed before. For what ever the reason I was not subscribed. You have a good channel. Take care, Ed.

[@goldsgarage8236]

Thanks Ed, I enjoy your comments. AG

[@pmd7771969]

Choose the powerband you want to run. Assuming your engine will make power at a given rpm. 3500 and up can work on a hi flowing headed 454

[@goldsgarage8236]

Thanks for all your comments and input PMD. AG

[@hardtail-gy8dk]

I worked in a building that one business unit did QC for refineries and stored aviation samples from plane crashes for testing. One thing today is its not really fair to call fuel octane still, it's blends of multiple carbon chains, many lower than octane, i remember as a kid my dad burning bush piles with purple and when the match was in the air you were heading the opposite direction and the whup went through you, today sometimes you can't barely get a fire to lite

[@goldsgarage8236]

interesting point, thanks for the comment hardtail. AG

[@pmd7771969]

All cars that ran on leaded fuel needed hardened valve seats so the valve wasn't pushed up into the head from lack on lubricant. Many people ran the older cars on regular and were sorry. 70 and up were the good ones that ran on leaded gas.

[@richm.6220]

i was wondering why you don't use Brass freeze plugs, i enjoy listening to your video's as we are never to old to learn what you have to say even tho, I am 80 yrs old and still enjoy hot rods. I have a running project 1940 ford cp. with a 327 with a tir power carbs setup and a new 5spd TKX tranny with a dodge 8.3/4' & it's has a 4.10 rear axle ratio. I'm using 80's 350 truck heads with the angle spark plugs to lower the compression to about 130 psi so, I run 87 octane pump gas. .

[@goldsgarage8236]

Wow, 80 and still digging, I hope to do the same. That will be a cool rod with the tri power 327. Actually i usually do use brass frost plugs and i am installing them on my current build for Will Casey. I just happened to have the steel (galvanized) ones . Steel plugs will outlast us but brass looks cooler for sure. AG

[@dylanfinch6186]

Thank you for the video. I'm learning all I can about this stuff. I'm about to take a healthy 6.0 and put a cam, springs, lifters, etc in it. I like that you are conservative. So, I have two questions. First, this LQ4 engine comes with 317 heads. The engine has a 9.4 to 1 ratio stock. I also have 706 heads from a 5.3. Everyone is telling me to use those. They would boost my compression to around 10.5 to 1. Do you think I would still run fine on 87 octane? Second, what cam would you run for daily driver, a bit more power, and mileage?

[@goldsgarage8236]

Thanks for the question Dylan. I am not as well informed on LS engines, however if you are building high compression, I would use the best pump fuel you can get. As for cams, the LS engines doe not need as much duration as the GEN 1 engines partly because they are all roller and can accelerate the valve faster on the ramp. Check the IVCP and calculate your DC and cranking pressure before you decide. The final result depends on many factors, the power/weight ratio of your car, gear ratios etc. Hope this helps. AG

[@jeffhopper3526]

Enjoying the "fire side chat"

[@goldsgarage8236]

Glad you enjoyed it Jeff. AG

[@roberthollinshead2325]

@Gold's Garage GM's advertised duration point is different than the aftermarket cam manufacturers, GM used the actual opening and closing points while the aftermarket cams are measured after what they consider the opening and closing ramps-some are .010" and some are .020". You would have to actually measure both of them yourself with a degree wheel to get an accurate comparison.

[@goldsgarage8236]

Thanks for your comments Robert. AG

[@Selmerpilot]

The issue with running high static compression ratings is the volumetric efficiency of the engine. If an engine running 12:1 static has very high flowing heads, intake, and high duration lift camshaft then it is likely that 100% or greater volumetric efficiency will be reached at high rpm. 100% VE means the static cpr ratio is being met. If you’re at 11.5-12:1 static and you’re meeting 100% VE then race fuel will have to be used. Many of these muscle engines run on the street with high static cpr ratios but it doesn’t matter as the heads and camshaft are not capable of reaching a high enough VE to reach what is the static ratio (11:1, 12:1 etc) thus 91 or 93 octane runs them without issue. Most ‘hot’ street builds with 2v CSB etc engines are maybe reaching 90% or so at best

[@SweatyFatGuy]

VE is more dependent on port velocity than it is about static compression ratio. Big lazy short runners aren't going to fill the cylinder at low RPM. Smaller high velocity longer runners will fill the cylinder much better at lower RPM, but it limits how much RPM the engine can achieve. The entire intake tract has to be considered, not just the ports in the heads. You're right though, engines with a cam designed to go to 7500 is going to have such a big hole in the VE under 5000 that they can probably get away with lots of compression and 87 octane.

[@goldsgarage8236]

Good point Selmerpilot, I plan to address this issue on a future video so thanks for the input. AG

[@manitoublack]

I'd take ethanol blended fuel every day of the week for performance applications. The cooling it provides is worth it.

[@goldsgarage8236]

Thanks for your input Manitou and thanks for watching Gold's Garage. AG

[@BrickandStein1999]

3rd gen mini cooper S has 11:1 comp (250 psi cranking spec ) and requires at least 89 octane. From the factory also running 8-9 psi of boost

[@brentonk461]

225psi cranking compression, and pump fuel for my street daily driver 379ci standard 4" bore 4 bolt main small block combo. Have run as high as 250psi with a Holden 6 on pump fuel. The other street strip daily driver combo of mine is a 327 2 bolt main 14:1 compression combo

[@goldsgarage8236]

Thanks Brendon, Are you in Australia?

[@dennisrobinson8008]

What kind of dyno numbers does something with that much cranking compression make?

[@kramnull8962]

@@dennisrobinson8008 How many times do you ask for forgiveness at night knowing you have 14:1 on a 2 bolt? Just kidding but still, goes all against the 1970's tradition of dissing the 2 bolt.

[@roberttraphagan3572]

An answer to the question about using regular instead of Ethyl in an L88 with 150PSI of cranking compression would be yes, and no. You could probably get by safely with retarding the initial timing and liming the amount of advance in the distributor. You should also mention not only the intake valve closing event timing having an effect on cranking compression, but explain that a later closing event will usually lead to more overlap, which causes the compression to bleed off.

[@goldsgarage8236]

Thanks for the info Robert. You have obviously given this a lot of thought. AG

[@pmd7771969]

I'd push 11.5 1 with fast swirl aluminum heads and the right dur cam. The higher a cam lobe lifts the valve off the seat it does hold the valve open a little longer. But few cams are streetable past using a 285 dur cam.

[@goldsgarage8236]

Thanks Paul, 285 is probably a good number. AG

[@jeffreyschweiger7960]

This is a late comment but you also have to consider if the engine has iron heads or aluminum heads. You need more static compression for aluminum heads because the aluminum will act like a big heat sink and wick away all that heat, iron heads will retain more heat and build more pressure. Heat builds pressure, pressure builds power.

[@goldsgarage8236]

Good info, thanks for commenting Jeffrey. AG

[@WesternReloader]

My static is 10.2:1 ish. I have a comp XE266HR12. Warm cranking compression is between 162-165 on all holes at 5200’ elevation above sea level. Adjusted to sea level 192 cranking compression. 4000+ lb manual Bronco. Runs great on 91 @ 32 degrees

[@goldsgarage8236]

Thanks Piercer, where are you 5200' above sea level? AG

[@WesternReloader]

@@goldsgarage8236 Los Padres National Forest an hour north of Los Angeles.

[@gabrielibarra5551]

So, essentially, however many degrees after bdc the intake valve closes will have the largest say on what the compression ratio is?

[@Larry-c7x]

Yep this is correct and if you if you follow his 61 versus the 81 after bottom dead center that's where he gets it back on the right now yep and I believe that will and his destination is going to make it to the definition for gas cuz that's what we're going to do run pump gas and see if I can do it with 13 to 1 or 3:27

[@goldsgarage8236]

Thanks for your comments. AG

[@antilaw9911]

I paused video to give my 2 cents of knowledge. 12.1 compression on pump gas, they used long duration cam to bleed off cylinder pressure at lower rpm.😊

[@goldsgarage8236]

I think you are correct Antilaw!. Thanks AG

[@garyradtke3252]

In the USA octane in the 60's I believe was motor octane and today it is an average of motor and research octane number (R+M/2). RON is tested on a special engine that can vary the compression ratio at idle and MON is tested on a special variable compression engine at higher loads and speeds. I think that I have read that many other countries at least once upon a time used only the MON rating which could be a different number than we use in the USA. I haven't thought about it in years so I don't know if that is still true since things are always changing. I'm not sure but I think race fuel in the USA is MON only.

[@goldsgarage8236]

Thanks for the education on fuel Gary and for supporting my channel. AG

[@JeffBarker-q2f]

I had a 64 Chevy II that had the “140” (last 3 numbers) cam and 12.6:1 compression ratio according to the guy that owned the car before me. The car had a 4 speed and 4:56 gears. It ran on the street fine but would really wake up at 5,000 +!

[@goldsgarage8236]

Sounds like a fun ride, Thanks for sharing. AG

[@lcxu1051]

With 150psi dynamic compression it will easily run on 87 octane fuel.

[@thejiggsman961]

FYI i built a 383 sbc that was run on the dyno it made 437hp on pump gas , cranking comp. was 195 psi.

[@goldsgarage8236]

Thanks jiggsman, that is a good number for a street 383. There is a video on my channel of Tom Winkler's 383 that made about the same. AG

[@pmd7771969]

If you could run forged parts in a 427 chevy, you could rev them to around 8k for short spurts. We made more power then the other gm guys that way. No rec port heads for sbc 327, 350, 455s back then. 320 cfm flow was awsome, then we'd port em.

[@Dube7666]

Great Video!! 22r (2.4 liter solid cam) street driven Weber 32/36, dual plane, stage 2 cnc’d heads with +1mm valves all port matched, ~9.8:1 , mid length header with 2.25” exhaust. Currently have a Crower (EFI stage 2) 216/220 @ .050”, advertised 270/276 with 430/430 lift and 114* LSA, which was obviously not the LSA I thought I needed, but I like the specs of the rest of the cam! Crower has the stage 1 Carb version (same specs as efi stage 2) with a 108* LSA, which I currently plan to buy to hopefully run 87 and get 25+ mpg city (with 3.73 gears eventually, 3.07 now). Your time is appreciated, and your thoughts greatly appreciated. Without dynamic compression measured, is ~10:1 on 87 octane likely, or is my head still in the clouds? Rare to find someone that tailors to street driven vehicles, so I’ll be checking out your other videos for tricks before I pull my motor back out. Currently have 9:1 pistons with 114* lsa cam and bought KB’s 9.7:1 hypereutectic and shopping for a better cam. If it won’t run well enough to stick with 87, it won’t stop me, but don’t want to ‘tune myself to death’ trying to accomplish the impossible if I just need another octane point. They have a stage 2 cam with 226/236, 286/290, .429/.443 with 108* lsa (which might be too big for low end desires and possibly too much dynamic compression to risk detonation but recommended upgrades of engine requirements align but they project a 3,000-7,000 power band versus 2,200-6200 for the stage 1) or another option is having them custom grind one similar to these specs, maybe more exhaust lift and/or tighter LSA. Thanks again for the video!

[@johnsheetz6639]

you talking about the Toyota engine? I always wanted to see how much they would make! I heard the 20 r head made more power if you know is that true?

[@Dube7666]

@@johnsheetz6639 every 22r owner that has spent a lot of money will tell you they won’t make much hp but the torque is pretty decent. I’m $3,000+ invested in the motor and with manual steering and electric fan (less parasitic loss than clutch fan) and 9:1, I maybe freed up 115-125 hp to the wheels. It’s not a very satisfying engine to sink money into but can expect to see 200,000 miles, it appears. They are described as tractor engines and I agree, so depending on what you want to use it for, you’re probably better off with any other engine in the world for hp unless you boost it… and even then, there’s probably a better alternative.

[@Dube7666]

@@johnsheetz6639 as for the 20r head, they have a hemispherical combustion chamber and a straighter path for air to flow in the ports for better velocity, so depending on your build, they could be a bolt on bunch of fun. They are also rare to find, which drives the price up.

[@johnsheetz6639]

@@Dube7666 that's what I heard before and the Jeep 4 L is one that's kind of the same. They both remain two of my favorite bulletproof engines though. They are engineering perfection for getting you there and back!😎

[@Dube7666]

@@johnsheetz6639 I always like the jeep cherokee and thought a low rev turbo with a straight 6 would have a lot of torque… but the Jeep emblem cost on every part adds up before it even begins.

[@David-vg2en]

I have an L72 with fresh .030 over bore and 11:1 forged pistons using stock cast iron heads with oversize exhaust valves. A concours nut and bolt restoration was completed in 2019. The car overheats and I am unable to drive it. I installed a new DeWitt radiator to help with the cooling but to no avail. I then checked compression and found it to be 250 psi all cylinders. The original cam was reground to stock specs during the restoration. The intake is a factory 2 plane (5069) and the pistons are TRW. Everything on this car is new or reconditioned and now has less than 300 miles. I am using straight 104 leaded. The timing is whatever Corvette Specialties set it to. I am using stock exhaust manifolds w/2 1/2" exhaust pipes and stock 355 rear end. The car is very difficult to take off in and between that and the overheating is not much fun to drive. Do you think that the compression is the cause for the high temperature? Any advice would b much appreciated. Thank you.

[@goldsgarage8236]

Thanks for the question David. According to the GM manual, the cranking pressure for an L72 425HP 427 is 150PSI, even though it was 11.0:1 Static CR. I suggest we start by recalculating or verifying your static CR. The bore is 4.25 and the stroke is 3.76. You need to know your combustion chamber volume, head gasket thickness and piston dome volume. If any of those things were changed during the rebuild, machining the heads or block surfaces, thinner head gasket etc, they may have increased your static CR. To determine your dynamic CR and cranking pressure you will also need the connecting rod length, 6.135" and the IVCP (Intake valve closing point) of your camshaft. Unless you already know this or the engine is accessible to degree the cam, it is unlikely you will have this information. Since your cranking compression is so far off, and the engine also does not run well, I am suspicious that something is wrong with the assembly. For example of the timing chain/gears were aligned incorrectly, (camshaft advanced a link or two) , that would close your intake valve even sooner, trapping more compression. Similarly if there were mistakes in the camshaft regrinding, same result. This would be an interesting project. Do you have the cam specifications? degreeing the cam would determine if either of these things were true. That would mean determining the centerline of the intake valve and then closing point. IVCP I would start with degreeing the cam. The engine has to be out of the car to do this. Let me know if this is helpful. AG

[@goldsgarage8236]

Looking at my response from last night. Two other possible causes of your condition could be ignition timing or a vacuum leak. Your timing should be about 36 degrees total at 3000 RPM with the vacuum advance disconnected. You should be using vacuum advance connected to manifold vacuum below the throttle plates. (not port vacuum) Also check for vacuum leaks. There is a large vacuum port at the back of your carburetor below the float bowl, hard to see it and I have seen this left open before. That would cause extreme lean condition, overheating and terrible running. This still doesn't explain 250 PSI which is too much. AG

[@carlpreston1680]

Check your thermostat in boiling water to make sure it opens when it should I found most of them don't work nowadays or when they should at least The most accurate ones I found are the Edelbrock thermostats

[@harryloibl5183]

Would you know perhaps what would be a better camshaft than factory on the vw 2 litre air cooled kombi, I think torque would be more advantageous, unless you think original cam is still a good choice. Thanks buddy 😊

[@goldsgarage8236]

Thanks for your question Harry but I don't have much experience with this engine and don't know enough about the application. Consider the end use, daily use vs. race, weight ratio, lb./cu. in. gear ratio, type of transmission, RPM range where you will need the performance etc. Hope this helps a bit anyway and thanks for watching. AG

[@harryloibl5183]

@@goldsgarage8236 ok cool thanks 😊

[@pmd7771969]

I've been an engine builder for years. Chanc3s are you won't run pump gas at that comp level. It's never worked before. Lsa also plays a role. With aluminum heads you can get away with 10.5.1 and cast iron heads non fast burn we ran 9.5 1 on 89 and 91 oct.

[@goldsgarage8236]

Thanks for all of your comments Paul. You clearly have broad and deep knowledge on this subject. Please keep watching and commenting. AG

[@scottbennett3119]

I think you can run 87 with a 12.5 compression motor if the cam has plenty of overlap, reduced spark timing, and running only at lower RPMs with light throttle. Didn’t Crower cams offer cams to run high compression engines on pump gas?

[@goldsgarage8236]

Thanks Scott. Cams with lots of overlap also have a late IVCP which bleeds off compression at low speed. AG

[@tomstulc9143]

I ran my 68 Pontiac GTO HO 400 on 87 pump gas. Listed at 10.75 to 1 bored it 60 over probably @ 11 to one then. No problems.

[@goldsgarage8236]

Another good example of what I was talking about. Thanks Tom. AG

[@pmd7771969]

Camshaft overlap helps the 3xaust gas get pushed out under pressure.

[@goldsgarage8236]

Thanks Paul. the signal from the header also helps to suck it out.

[@michaellecount8510]

Great video! Thanks for sharing.

[@goldsgarage8236]

Thanks Michael, glad you enjoyed it. AG

[@Chris-bn1bn]

Btu stands for British Termal units witch as I understand things is btu is heat potential and not potential energy. Alcohol does burn at a lower temperature but continues to expand longer. Yes you need more of it than gas, but to say that it doesn't produce more power is correct or not, depending on your engines compression, boost, lobe separation. Alcohol will permit you engine to make up to 3 times more power than gas if you build for that purpose. Thought I'd point out the way you phrased that comment. Like your video's.

[@goldsgarage8236]

You are correct Chris. Alcohol has less BTU/gallon, but that can be compensated by a richer F/A ratio. There are many applications of Alcohol race cars, including Alcohol Funny Cars that make huge power. Thanks for your comment. AG

[@joeyjojojr.shabadoo915]

THIS IS THE VIDEO THAT I HAVE BEEN LOOKING FOR. I am looking to build a Normally Aspirated LT Gen V Direct Injection Small block to as large as I can get it in a standard deck (454cid I believe, 4.185" Bore x 4.125" Stroke) for a 4WD application, so max 6-6500 RPM, and was looking for good camshaft information, as I want it to run on 87 Octane daily. I know that the Direct Injection will allow me a bit more compression ratio due to it's design and knock deterrence because of where in the cycle the fuel is introduced, but I still had questions for overall CR. GM currently sells a 10.5:1 GenV for HD Trucks rated for 87oct, so I was hoping to run about 11.5:1 with the proper cam selection. this helps immensely. Thanks.

[@davidreed6070]

The bore and stroke combo you mentioned is 496 cubic inches. I've built several. It will pull the truck very well

[@steveamnmn]

@joeyjojojr.shabadoo915 Respectfully, you might want to reconsider your rpm goals for your 496 V8. With that long, 4.125" stroke, 6500 rpm would put your mean piston speed at 4469 ft/min. That is getting closer to NASCAR territory than to normal street engines. Generally, even a pretty hot street engine is pushing the limit of mechanical reliability around 4000 ft/minute piston speed. For example, a hot 350 Chevy small block with a 3.48" stroke at 6500 rpm has a mean piston speed of 3770 ft/min. Also consider you are slinging heavy pistons and rods in this big motor, making the stresses of rapid directional changes magnitudes greater. The good news is, with that huge displacement you won't need such high rpm to make big power. Since you want to run 87 octane, I would suggest contacting a custom cam designer and ask for a cam that, with your increased displacement, will produce about the same cranking pressure as the stock, direct-injected motor. For your 4x4 truck application, think hard and realistically about the rpm range where you will run the motor most of the time. Huge mid-range torque may satisfy you substantially more than an extra 1000-1500 rpm on the very top. Share those goals with the custom cam maker and you'll have a real beast!

[@goldsgarage8236]

Thanks for the question Joey, and I apologize for the very late reply. I just noticed it now. Unfortunately your question is a little out of my wheelhouse. I agree that direct injection should allow more CR and cranking pressure but I don't have enough experience to say how much. Typically I would recommend keeping your cranking pressure

[@joelmclaughlin2558]

It works out to 454.​@@davidreed6070

[@tomstrum6259]

Not all engines designed the same as regarding Anti-Knock Chamber--Piston shape issues.....With '60's high compression Factory production Tolerances & 100 octane Pump gas available, 0.040" to 0.060" head gaskets & high domes were common.....When doing a build Today, Thinnest gasket (to whatever Piston to head clearance you comfortable with), Aluminum heads & Shortest piston Dome to give 0.040 Squish gap & using the Coldest range possible Sparkplug with a hot ignition is usually a good direction build plan.....With hopped up Pontiac engines tendency to run Hotter than wanted, It's Interesting that Pontiac used "Reverse Flow" coolant design to Cool the head First & then the block.....

[@goldsgarage8236]

Thanks Tom, I don't think there was as much attention paid to squish back then. Most OEM haled at last a .040 head gasket and then .030" minimum deck height. I recall using a thin steel head gasket on my Z28, we painted them with silver paint. They were about .015" and I did deck the block so we were close, but we didn't call it squish.

[@mr.b2107]

Stanley Meyer said once that hydrogen was and is the secret additive to gas that raises the octane level. Hydrogen has a 130 octane rating.

[@Walkercolt1]

Add hydrogen to gasoline and you get... an EXPLOSION! An ENORMOUS one! Stanley Meyer knows NOTHING about organic chemistry and LESS about internal combustion engines!!! He probably thinks burning COAL or GRAPHITE in a DIESEL engine is VERY EFFICIENT too! Herr Deisel and his assistant (if you could FIND a scrap of them!) could tell you HOW efficient it is! Their "test" putting a QUARTER of a teaspoon of coal into a running diesel engine destroyed the engine, the lab, Herr Deisel,his assistant (they never found enough of either to bury), the BLOCK where the lab was. Doktor Nobel estimated the destruction to be equal to 500 KILOS of high-velocity dynamite. Hydrogen DOES NOT have a 130 octane rating, NATURAL GAS (methane) DOES! Hydrogen has about a 105-110 octane rating-dis-information at it's best!!!

[@goldsgarage8236]

I did not know that, thanks for the input. AG

[@johnrisher3007]

What is cranking pressure and how do you figure out how much

[@goldsgarage8236]

Good question John. Cranking pressure is simply compression pressure that you can measure with an inexpensive compression gage that you can buy from any auto parts store. it screws into the spark plug hole, (disable the ignition) then crank the engine over a few revolutions or until it stops climbing. For a street engine on pump gas I like to see 160-180PSI (pounds per square inch). Compression makes power but if you have too much you can cause detonation which can damage the engine. To calculate it on a build, first determine the static CR. You can use the Summit on line Calculator. You need to know your bore and stroke, combustion chamber volume, piston dome volume, deck height and head gasket thickness. For street, aim for 10:1 for steel heads and 10.5:1 for aluminum heads. Then you can use the Wallace Dynamic Compression On Line Calculator. Now you also need to know the connecting rod length and the IVCP (Intake Valve Closing Point) of your camshaft. The result will be your dynamic CR and cranking pressure. Hope this helps. Let me know. AG

[@krakhedd]

150psig @ sea level is 10:1 compression ratio, and the higher you go the worse that is Direct injection & advanced engine electronics is how my turbo 4 runs an OEM 13:1CR on 87 octane gas in Buffalo NY

[@goldsgarage8236]

Thanks for the comment Krak. AG

[@scotthatch4548]

You are aware that dynamic compression is just that dynamic and as you go up in rpm airspeed goes up and you are at full static compression .... Also you can't compare advertise duration because gm used .001 tappet lift and comp uses either .006 tappet lift or .012 tappet lift .. and flow down at those numbers does not happen .... That's why .050 tappet lift is on most cam data sheets

[@goldsgarage8236]

Thanks for your comments Scott. All good points. Watch for more on the subject.

[@chads3149]

So my stroker 427 sbc has a cranking compression of 210 psi. The builder said it has a dynamic comp of 11.1 to 1 he recomended i run a minimum of 100 octane i so so by adding an octaine addative. To no ethanol 91. Cam has 272 duration at 0. And a 109lsa on exhaust 112 on intake. Is he out of line or could i run 91 octane without ehanol. I believe that fuel is non oxygenated as well.

[@goldsgarage8236]

Thanks for the question Chad. I think your engine builder is correct. With 210 psi cranking pressure, you will need race fuel.AG

[@ScorpionRanchTX]

Cranking pressure is measured at very low RPM. You might even be getting over 100% VE at high RPMs. How would that effect the pressure then?

[@goldsgarage8236]

Good point Scorpion. VE at high RPM will increase peak pressure and MEP, which is the average cylinder pressure during the complete down stroke. Typical MEP would be 10-15 times atmospheric pressure. AG