383 Stroker Engine Build Part 5 (Compression Ratio)

In Part 5 I discuss Compression Ratio and haw to figure it out Please excuse the choppy editing It's a new Camera and editing software I'm still trying to get the hang of it Enjoy

[@vsetkoumiera7683]

Absolute best explanation of compression ratio that I’ve EVER heard !!!

[@christophermclaurin7479]

This guy is a wizard! Thank you for sharing your years of experience. In depth!

[@onyxdragon6980]

I totally appreciate how in depth you do with explaining all of this!!

[@kevinw8538]

I literally turn your channel on and listen to like a talk radio show while driving all day for work.

[@Tricolor610]

Hi I watched your beginnings years ago and they have always been very informative. Now I want to restart my Iroc after 6 years, it has a 383 stroker in it. The oil pressure was always ok cold ... when it got hot I had almost no oil pressure. I have now bought a HV pump in the hope that it will get better. The engine has only done 2000 miles, so it is still new. Greetings from Germany

[@MrCbell57]

First time I’ve ever understood compression ratio. Nice!

[@NewHavenMotorsports]

You should do a video on Dynamic compression ratio.

I enjoy your videos and you certainly know your shit and that is why it surprises me that you leave out the valve relief volume that as you know will increase you volume lowering you compression ratio. I know that it's a pain in the ass, but these videos that are the best that I have run across are for people that don't know these things and skipping over them when you do such a great job on the rest somewhat spoils your effort to teach proper engine building. Again, thanks for doing this and I wish that they would have been around forty years ago.

[@BrianW2979]

Great video series, very well explained for a semi novice gear head. Learning lots of new things and understanding old things a lot better.

[@juliennacer8871]

Why do you only recommend 9.5:1 compression for street performance motors? My impression was that 10:1 compression with aluminum heads was still perfectly safe with 91+ octane premium pump.

[@Darren87aero]

thank you very much for making these videos!!! I want to stroke and rebuild a vortec motor for a future project, I wouldnt have a clue if it wasnt for fellow gear heads like your self making these videos.

[@jeffro1234567891]

Excellent video. I wish you were my auto tech teacher back in the day. I would have learned a lot more. I remember my oldest brother telling me he changed out the head on his old flat head Chevy and getting more horsepower and having the fastest car in town. This was in the 60's when he drag raced down the main street of town at night. I understand now that he increased his compression ratio. Your the best and I always appreciate your videos.. Just bought a 1976 350 Chevy engine and putting it in a 1956 GMC.

[@hp858]

Another great video; the water analogy creates a visual for volume and compression. Mike

[@Myvintageiron7512]

THX

[@ryanplatt5370]

Thank you for this sequence of 383 stroker builds. I'm from Australia and have a 2001 hsv maloo R8 with a 383 stroker in it running at 11:1 ratio, it has a 235/251 @111 crow cam in it 285 inlet and 305 exhaust outlet. It is also running on a 100-150 shot of nos and is tuned to 98 octane fuel. This sequence of videos will help me for future builds, you are an absolute legend 👌

[@nrainfidelforlife]

Very cool. I had no idea that compression ratio was that simple. All I knew was the higher the compression the higher the octane I had to use! Ty.

[@johnmckamy6398]

could listen all day. great information.

[@jayamd3579]

wow thanks dude, Compression ratio has alsways been a mystery to me, great explanation

[@williampommeranz6821]

Nice series. I'm OG building a gen 1 stroker for my 65 Impala. Yah, LS swap better power per dollar, but car shows are old and new hot rodders getting together. In my younger days, I laughed at the "flatheads forever" gang with my overhead valve sbc. History doesnt repeat, but often rhymes. Im the gen 1 crowd, not fighting technology of the LS, but keeping the orange painted cast iron stroker/sleeper thing alive.....surprising the LS normally aspirated crowd. As for back as the 90s, power adders bored most hot rodders. If a car back then would make a pass in the 11s....everyone would want to check it out. If the car had nitrous (turbos not around yet), people walked away. If no nitrous, they would talk for 15 minutes. You used to build cars for 500 hp. Not be boared with them.

[@evanriemer3717]

When you say 'pump gas' what octane are you referring to? I'm building a stroker in college this year and want to run it on pump gas because $14 a gallon for race fuel is just not in my budget. I'm just not sure how high of compression ratio I can go on 91 before it starts to hurt the motor. Pulling a 350 out of a C60 grain truck, got a 400 crank and rods, and hopefully putting vortec heads on. Doing a very, very budgeted build. These videos are highly helpful and I can't wait to see the next one!

[@v7nf]

Ive learned alot ,thanks so much,fortunately for me Ive got someone in the family whose a machinst and hes gonna help me with the block crank and pretty much everything,but Ive learned alot from you!Its going in a jeep by the way..

[@Myvintageiron7512]

That's awesome

[@v7nf]

@@Myvintageiron7512 yea Im a welder,past 26yrs or so,Ive so far rebuilt it from ground up,rewelded frame panels suspension y link,rebuilt everything etc. Ive always been fascinated with engines,your videos are great!

[@caliman823]

Thanks for the videos, your giving the poor man a fighting chance with knowledge which save money. I would like to see a video on compression and altitude and how that effects octane fuel needs. I live in 6000ft.+

[@jonathanlawson4667]

Thinner the air the less combustible and the more air you'll need. Say you're running a 650 carb at low altitudes and it's perfect so you go to a higher altitude where there's less oxygen in the air the motor consumes so that 650 that run excellent will have to be jetted down for a higher altitude I hope this helps

[@southgajeeepers2416]

Awesome ,thanks a lot for all the time you take your videos are always on point and for me it all clicks after watching them I can't wait for next one.

[@arlanmaxwell9932]

I am planning to build one. Very helpful!!!!!

[@mikespencer9913]

When you build a Stroker engine, you compensate for a drop in Deck Clearance by moving the pin up toward the top of the piston. What you haven’t addressed is how much farther the piston travels DOWN! How much room is there (typically) to allow the piston to stay ‘square’ to the block before it falls out of the sleeve? Just curious…

[@ALLMUSCLEUSA]

Nice videos, tons of great info. When you say pump gas, are you talking 87 octane? From what I know some cars come factory with 10.5:1 up to low 11:1 ratios and are suggested to be run with premium fuel 91 octane. Whats a good ratio to run on 91 fuel. Working currently on a Chevy LT4 engine with a factory ratio at 10.8:1.

[@Jay-fb2lv]

I run 11:1 with aluminum heads all the time on premium gas and 34 degrees total. Works just fine.

[@scottwest1813]

That was an awesome explanation brother.

[@Myvintageiron7512]

Thanks!

[@MALOX13RAIDERS]

I fucking love this channel

[@adamhoward2393]

that drawing is going to have terrible compression with that cylinder to bore clearance probably just blow-by lol.

[@matthewhummel6023]

Fiine explaination.

[@tonykelly5141]

Just wanted to start with a subscription and a serious question. I recently had a bit of luck lately and piece by piece have been able acquire a 30 over 350 block. The man who was building this motor passed away before he could assemble it unfortunately. The block is 4 bolt main, 1972, has been decked and all the machine work has been done. Line bored, cam bearings, freeze plugs and paint. Since the passing of the original owner, some of the parts were separated but I was able to get everything back together and this is what I have. Iron Eagle steel crank, 6 inch Eagle H beam rods, 30 over JE flattop pistons, all the bearings are Mahale mains and rods, rings also. Double roller timing chain and gears by comp cams. I realize that this motor will have to be ran on race fuel. But since I live close enough to Bristol's Thunder Valley race tracks I can hear the top fuel dragsters and funny cars do burnouts. I don't have a problem with race fuel, especially on street fight night. I'm a old school hot rodder but I've never been able to afford a motor of this potential caliber. I have a Victor Jr intake and a street demon carb. I have a NOS system also. I don't know what type or kind of cam and lifters I should use. Nor do I have a proper set of heads. I do have a set of old school double hump heads that are maxed out. Big valves screw in studs, comp springs and roller rockers ,push rod guides , ported to intake gasket, polished exhaust port and combustion chambers. Can you please give me some advice about the cam and lifters and what kind of heads do I need? I know those double humps would be the best thing going 30 years ago but they aren't going to do justice for the motor and potential horsepower I suspect this motor is capable of. Can you help steer me in the right direction.??

[@Myvintageiron7512]

Well first off get rid of the double hump heads they belong in a museum or on a period correct restoration vortec heads in stock form will outflow them, however I do not recommend vortec's for your engine either. A 6" rod motor needs radical solid roller cam mild cam profiles will cause a 6" rod motor to have destructive detonation this is a whole other topic I won't get into it now but trust me it is a thing with these engines, next you will want a set of AFR or Brodix heads, I would contact Howard's cams and tell them what you're doing. They can recommend the correct cam, they are very good at this. the one thing you did not mention is this a 350 or a 383? That is important to know before you buy the heads so you can figure your compression ratio. The heads need to flow at least 300 CFM's on the intake side, your cam will be in the neighborhood of .650 lift and 236-242 duration@.050 but again you need to discuss cam selection with Howards you will also need to make sure that the valve springs are set up with the correct spring pressure and lift specs for the solid roller cam that you choose, this will require conversations with Howards and AFR or Brodix

[@tonykelly5141]

@@Myvintageiron7512 thanks for the info. I found some paper work the original owner had on this motor. It came out of a 1972 split bumper Camaro. 350 4 speed. The owner was a drag racer and worked in a machine shop 15 years. This motor was bored 30 over. We also made a discovery in the barn that his wife showed us just yesterday. 2 1972 split bumper Camaros. Both are in rough shape but fixable. We even have a matching numbers motor for 1. Unfortunately the motor I have is not one of those cars. It was turned into a drag car and sold years ago.

[@tonykelly5141]

@@Myvintageiron7512 400 crank so yes.

[@MrCbell57]

So how do you figure compression ratio before you have the parts? You said we need to know this before we build the engine. I certainly don’t want to have parts that I buy and then find out they won’t give me 10:1.

[@Myvintageiron7512]

www.rbracing-rsr.com/compstaticcalc.html

[@imperialgtr]

just want to say thanks for taking the time to go through this, im in the uk so have zero v8 knowlage, really looking forward to heads and assembly, are you doing any porting on it? also is quench ( read from below comments) the same as squish?

[@jjpoissant]

I want to be there to watch the first kid tip his Subaru on its side and try to pour water in it to measure his compression because he didn’t listen to the whole video. :)

[@johnrebello7059]

I'm building a 383 stroker for my 1986 corvette.im looking at 500 horsepower it will be a weekend cruiser but I do want the horsepower.im going with scat forged stroker crankshaft and forged pistons.my question to you is can I run 10 to1 compression with 93 pump gas with no issues?

[@jessesyfie7244]

Would u be doing a video with the dynamic compression of an engine which is tied in with camshaft timing and further on about this? Dynamic compression is way more important on how an engine with run and preform than static compression. When u say pump gas u talking about 87 or 91 octane? My present project is going be a 70s 350 with 416 305 heads 59 to 60cc chambers, .015 steel shim head gaskets and 12.3 cc dish pistons to make 9.9 to 10 to 1 static compression. My cam will be Howard's 255/261 advertised 201/207 duration @50 with 114 lobe centers and my dynamic comes out to about 8.4 by the formulas. I know 9.5 static is about the safe zone for pump gas but I want push it to 10 for all I can get on 91 octane and short camshaft. From what I studied 8.5 dynamic is about the maximum for 91 octane iron heads or what would u say im curious. This is going be a test engine and going have a tight piston quench of .040 to .045 to stay away from detonation.

[@christophercostantini5361]

Could you not measure the length of the cylinder in both positions and take the length of the head and the gasket into account afterwards, rather then using water?

[@mastmec]

go fast math also has a really good calculator.

[@ChielScape]

If you're gonna do a more in-depth video of compression ratio at some point, it'd be cool if you could touch on subjects like Squish/quench (and decking the block to achieve this), aluminum vs cast iron heads, piston, head and valve coatings, thermostat temperature, camshaft profile and other things that affect susceptibility to knock/detonation, and how much compression one can run when taking all those into account, as opposed to a generic engine.

[@markmaleski818]

ChielScape Did you know they make schools for that? & there is a calculation for this too. He just told you that. Do your math. Don't ask him to help you. all each one by one. Plus it's top secret! So? Haha

[@ChielScape]

Are you stupid? Considering your blind faith in the American educational system, I think I know the answer. Not to mention your reading comprehension.

[@markmaleski818]

ChielScape cool your jets Cowboy or raise your octane level, check your combustion chamber CC,'s and get comp. ratio! And your big dish Pistons you got! Deck you block smart ass, and see what happens Then. Fords have more positive deck hight and need it done. Not Chevy's so much and you don't learn this in public or private school, try doing it all your life Capt. Squelch. Try Flame travel.

[@markmaleski818]

ChielScape you just asked 10 different things and answered your self. Just raise your octane and fix the flame travel & polish combustion chambers so not to have hot spots.

[@ChielScape]

I asked for him to make a video on these things for people to see. I know them, that's why I can mention them in the first place. Difference is he can explain them better.

[@colinthurlow7148]

Hi that was very good video as all of your videos are just a question i have just built a 383 just ordered a pair of afr heads 180 runners 65cc combustion chambers but i made a mistake and ordered 180 runners and 75cc combustion chambers would this be ok or not many thanks

[@jrgsxr33]

excellent explenation

[@patrickdunne730]

Great work thanks.

[@southjerseysound7340]

I see so many people running too much compression these days.I think a lot of it comes from the new fuel injected motors that run a high CR and they think it carries over to older motors.

[@romanviking1007]

Finaly ball larked it lol. Sweet

[@frankc1430]

Which engine is better to beef up and make power? A small block 400 or a 383 stroker?

[@11rollercoaster]

great video.. thanks.

[@scottsinfl]

great calc.

[@kafoure93]

my 94 camaro with the lt1 runs 10.5:1 compression. How is this achieved with just running 93(premium) octane.

[@Nemesis_0311]

Different variables, Heat, altitude,cam bleed, there are a lot of engines with 11.0:1 or more on 93, static is different to dynamic most cams will bleed a tiny amount of compression during intake so your dynamic comp could be 10.2:1 give or take. but if you're running 10.5 on a lt1 you should have researched this kinda thing before you risked destroying it by not knowing. but yeah 10.5 is easily achievable on 93.

[@KingJT80]

remember, your LT1 is reversed cooled and has EFI. that has a lot to do with it..

[@randy3536]

How accurate are these stroker rotating assembly kits that say " compression ratio will be X amount with a 64cc head , 76cc head" , ect. Im building a 383 and have a set of 906 Vortecs id like to use on it. Your videos are very informative. Thankyou for making them.

[@Myvintageiron7512]

They are pretty accurate but remember when they say what the ratio will be with a certain head you need to know what gasket they are using and what your deck clearance will be, they will usally use the standard .035 DC and .040 gasket thickness also you need to know what piston they are using I would jump on the RSR calculator if I were you and plug in your Vortec head chamber they have a pretty tight chamber you will probably need a pretty big dish in your piston and a thick gasket to make it pump gas friendly

[@sandysullenbarger3717]

just saw your video on compression ratio,my question is this,i bought a car they said was a 350 bored to .30 over..355 c.u.,one of two questions,i have world products s/r tourker heads,and i,m not sure of the c.c. size,they cam in 67 and 76,the other question is,the pad on the front of the block,the numbers and letters are ground off,soo i,m not sure what it is for sure,or could the block have been dected...it has a mild cam,and whether i run reg.gas,or high test gas,the performance doesant seem to change,except the idel seems to be smoother with the high test fuel,..and idea what the static compresson might be.?...thx for the help...stu.

[@shakes883able]

I could really use some help I'm assembling a 388 Stroker am I static compression ratios have come out 8.97. Are these numbers acceptable and what are my cam limitations

[@damonvessey2609]

Does deck height ever change, besides decking the block? Stroking and buying pistons, how would you know the deck height before hand?

[@Myvintageiron7512]

You need to measure it

[@96xr400]

When you say pump gas are u talking about 87 or 93 octane, we have 87, 90, and 93 here

[@jameson6930]

Many thanks

[@shanearmon9683]

Squish needs to be discussed badly when talking CR on street motors

[@hamcheesecola]

When you say pump gas what octane are you referring too?

[@flamehara8478]

Layne Willingham normal pump gas usually has an octane of 87

[@86djtaylor]

When we say pump gas, we mean the highest octane you can get at a gas station which is mainly 91 or 93 octane. Generally, when someone says "I make ___ hp on pump gas" they mean 93 octane.

[@brendanhile1801]

91 is the lowest octane in australia, 98 is premium. I run all my vehicles on 98.

[@monkeywrenchization]

I worked at an engine machine shop many years ago. One of the terms used during the calculation was swept volume, but I don't remember what that was. You didn't mention this, is there a different name for it?

[@Myvintageiron7512]

swept volume is the area the piston displaces clearence volume is the area above the piston compression ratio is a comparison of swept vol vs clearance vol

[@dogbuggy32]

great stuff thanks

[@angelamaldonado3568]

Thanks for making this video, your videos helped me build 3 engines. I am building one for my own and I still have my doubts. Because I dumped money in it. so when my sbc was at the machine shop the deck was shaved off to 0. Bore size is .060 flat head pistons and the heads that i installed are the 65cc, 195cc AFR aluminum. When the block was done i was told that C/R is 10.9:1 but i just want to double make sure... is there any way that you can check for me. Thank you will help a lot.

[@Myvintageiron7512]

if you use a .045 head gasket it will be 10.9 to 1

[@krazn8]

Are you going to finish the 383 videos or is #5 the last?

[@MrAdamdavila]

how do you feel about 10.5:1 on pump gas

[@Maxumized]

That’s what she said

[@joesills3153]

Thanks for the great videos. I just finished assembling my 383 stroker and the C/R is 10.24 to 1. I have aluminum heads with 70 cc combustion chamber, .039 head gasket, piston is .008 in the hole, with 5 cc valve reliefs, and bore is 4.030. To get to 9.6 C/R should I buy another set of pistons (dished) or maybe thicker .065 head gaskets. Any suggestions?

[@Myvintageiron7512]

10.24 to 1 is fine with aluminum heads run it premium fuel only of course

[@joesills3153]

I noticed Blueprint Engines runs 10.0 C/R on there 383 with aluminum heads. So why is a Higher C/R ok with aluminum heads as opposed to iron heads?

[@Myvintageiron7512]

Aluminum heads remove heat much faster so more comp is doable

[@curtthompson2787]

What is the difference between static and dynamic compression ratio and which do people usually go by? Using th rsr calculator and plugging in all of the stock measurements from the vehicle motor build measurements sheet this calculator ends up about 1 full point greater that the actual rates compression. Using that I get 9.2:1 for a 78 350. This should be 8.2:1. I put in the numbers from the build sheet from Chevrolet. How is this possible?

[@Myvintageiron7512]

your leaveing somthing out probably piston dish

[@curtthompson2787]

@@Myvintageiron7512 I'm glad you said that. That was exactly it. I mistakenly entered .12cc instead of 12cc. Not sure how I did that, I entered it correctly on other sites so I didnt know why this was different. Anyway, it ended up dead on for the stock 350 and gave me a good idea for the rebuild. Thanks a ton. Great videos. I've learned a lot following this channel.

[@garymeredith2441]

Vantage okay I watched your video about compressor racial so what is the highest compression ratio you can build an engine and still run 91 octane fuel .

[@Myvintageiron7512]

I would stick to around 10 to 1

[@alanster18]

Thank you!

[@joseallmotor]

how can i know what camshaft do i need to put in my car when i stroke the engine

[@Dan-ig1xe]

what compression ratio do I need to run 87 octane and make decent power? I already have 64cc heads to I'd need dished pistons

[@brock6560]

So if you have a larger cc head and still maintain a 9.5/1 ratio is that better or do you want to still have a smaller combustion chamber head. Also how do things change if you want to run a turbo or supercharger? I'm just new to this so don't laugh to much at my questions.

[@Myvintageiron7512]

It depends every engine is different there is something called surface to volume ratio in general it is better to have a larger chamber because of more A/F capacity as long as you can maintain a compression ratio that you want the key for any chamber to work well is two fold the chamber needs to promote turbulence (rapid mixing of the A/F mixture) the other aspect you need to find a happy medium as far as size goes, too large of a chamber and the surface of the chamber absorbs to much heat and it robs heat energy that should be used to make power to small and there is not enough area for the A/F charge and you limit the power even with a good induction and exhaust system a chamber that is to small can limit the amount of A/F that can fit into the chamber, Because of this you need to do allot of research on your engine to find out what does and does not work well based on what other people have done with dyno testing and so forth.

[@danvrana277]

Have you ever built a: IMCA Late Model Motor? What's your recommendation on that type motor? Chevy board .030 = 355 Thank you

[@Myvintageiron7512]

Chevy's are the cheapest if your going to get into the IMCA game stick with Chevy unless you have deep pockets

[@SzymekCRX]

Is it possible to mount a blower on a stock SBC without rebuilding it ? Ie. is it possible to lower the compression just by using a thicker gasket ?

[@Myvintageiron7512]

Yes it is possible but you will only be able to have fun for a short time because most likely the engine will die a very quick death I suggest you watch Roadkill here on You Tube Fryburger and Finigan put a blower on a stock smallblock in a Jaguar and called it a draguar! Like I said they had fun for a short time but really a blower should sit on a blower engine one built for it hope this helps

[@SzymekCRX]

Cool as usual ! :)

[@aaronburleson2454]

Is 10.85:1 too much on pump gas aluminum heads

[@aaronburleson2454]

I'm having some trouble getting it tuned runs rich

[@edwardgray1532]

So are you saying a bone stock 1968 corvette with a L79 327 with 11:1 compression wont run on pump gas today? What did they run on in 1968?

[@Myvintageiron7512]

no it probably wouldn't the heads were not designed as well now if you put a set of aluminum heads on it it probably would they had 100+ octane at the pump in 68

[@Myvintageiron7512]

we had 102 octane premium leaded fuel at the pump in 68

[@jonathanharris6699]

When putting a stroker crank in an engine will tdc change, bdc change or both?

[@flamehara8478]

If using the same length connecting rods as you were with the stock crank, tdc and bdc will change, because they are moving farther up and down in the stroke (a stroker motor increases displacement by increasing the length of the stroke, and to do that a piston has to travel farther in the chamber)

[@marcusharper4793]

I'm in the process I'd building a 383 stroker right now and the heads I was looking at have a 64 cc combustion chamber putting me at about an 11:1 compression ratio... could I run in premium? Haven't bought the heads yet so I can still reconsider

[@Myvintageiron7512]

NOOOOO! don't do it! You need to be at 9.7 to 1 max for pump gas and enough timing to make power 11 to 1 needs 106 octane

[@marcusharper4793]

Myvintageiron7512 awesome thanks for the info saved me a hell of a head ache

[@mikeriley8677]

Have you ever built any engines for marine applications?

[@Myvintageiron7512]

Yes

[@moto_rad]

Why are little hondas and sport motorcycles able to run around 12:1 without issues?

[@Myvintageiron7512]

Aluminum gets rid of the heat much faster I ran 11.3 to 1 compression in one of my Big Block Chevy engines on pump gas with Aluminum heads it worked try that with cast iron and yer engine ids doomed

[@moto_rad]

Awesome, thanks for the knowledge! I've been watching so much of your channel this past week, I am so glad I found it recently.

[@rzradventures]

@myvintsgeiron7512 Highest we have here in cali is 91 octane. Would you run 91 with 10 :1 compression on a 327?

[@Myvintageiron7512]

yes

[@rzradventures]

@@Myvintageiron7512 thank you. Your videos are a wealth of knowledge. You're the man!

[@8172008]

Well, my friend, I'll have to disagree with you on one point. My daily driver in 1986 and '87 was a Nova with an 11to1 comp ratio, and it ran perfectly. My friend who actually owned it was a drag racer (bracket) and I have to believe him. This thing really snorted, it was nice, just sayin' :---))))))))))))))))

[@Myvintageiron7512]

Did it have Aluminum heads

[@Myvintageiron7512]

Do you know for sure it was 11 to 1 or is that what you were told I have tried it more than ounce and it does not work well on pump gas

[@dtorr222]

11 to 1 on pump gas?? and it's a daily driver ?? sorry man I call BS I have built a bunch of these engines with 11 and 12 to 1 compression and I can tell you there ain't no way you had that kind of compression on a carbes small block with pump gas I don't care what your friend told you he's full of it

[@Stainlessslayer]

Dave I wouldn't say it's impossible. In 86-87 there were better premium fuels at the pump. up until last summer I could get 104@the pump.

[@frankc1430]

What is the most compression ratio you can safely run on premium pump gas?

[@Myvintageiron7512]

10 to 1 with iron heads

[@frankc1430]

@@Myvintageiron7512 what about with aluminum heads?

[@frankc1430]

You said 10 to 1 with iron heads. Is it any different for aluminum heads?

[@schussler07]

Is the build still goin?

[@ninjapumkin]

Can a person use air to measure that volume at tdc and bdc

[@bryonweatherford1772]

Sure, but then how your going to measure the volume of air.

[@Stainlessslayer]

I have an iron headed 383 with 10.2:1 (figure is without deck clearance ) am I S.O.L. on pump gas hopes? or could a cam with a bit of overlap save me?

[@Myvintageiron7512]

How much deck clearance do you have

[@Stainlessslayer]

Myvintageiron7512 I have not measured yet. I did use the recommended calculator and found if it's at least. 010" in the hole I should be at 9.9:1. BTW Thanks for sharing that. I'd been using Wallace racing calcs and my numbers have been different every time.

[@Myvintageiron7512]

If the block hasent been decked it's probably more like .030 it should be fine

[@Stainlessslayer]

Myvintageiron7512 Blueprint assembled short block, so I'll have to measure to know. Sadly they do not give a build sheet. thank you so much for your replies. Liked, subbed, and shared.

[@MrCWH5]

Where is part 6 :(

[@Jordanrhart]

Ive read lots of conflicting information on what kind of compression ration I should run on Iron heads with pump gas. Some recommend as low as 8.1:1. I feel like the 9.5:1 you recommend is pretty reasonable / safe. If I target 9 to 9.5 ish dynamic compression I should be safe on 91 octane right? Thank you for your videos! I'm learning so much!

[@3825maverick]

What is the best pistons for 383 stroker

[@3825maverick]

My email is [e-mail]

[@brad9240]

Asking that question means you need to do more reading before you get an answer that's at all meaningful to you. There is no "best." It's all application specific.

[@bridgetkrams4083]

How do you feel about e85 in something running around 13-1?

[@Myvintageiron7512]

E85 works great should be fine

[@bridgetkrams4083]

Awesome, appreciate the info.

[@benkalinowski5834]

9.9 for carb on pump gas Is that 91 89 87 or 94

[@Myvintageiron7512]

91

[@benkalinowski5834]

@@Myvintageiron7512 I have fuel inj tuned what's a safe level I have a 383 Aluminum heads and wiseco stroker pistons 9.9 and I have a felpro steel hg that's paper thin I thought it was roughly 10.25 I got 200psi on my compression tester I can only get 91 here to

[@MylesZ06]

Can I lower my compression ratio on a 383 Stroker from 12:1 to somewhere around 9:1? Would changing the piston heads or stroke length lower it?

[@davidtaros1297]

Myles Z28 change to 76 c.c heads

[@flamehara8478]

Myles Z28 changing the stroke length would be detrimental cause you'd have to rip the whole thing apart again, a set of larger combustion chamber heads would at least be a a step in the right direction

[@MylesZ06]

Flamehara lol junkrat. And thank you, would piston heads make a difference too?

[@86djtaylor]

I can explain all of the compression issues to ya. If you have a 12 to 1 383, you have a horsepower and torque monster, but, lol, unless you run 104 octane or similar racing fuel, your going to have detonation issues. Detonation will kill your motor. You could crack pistons, have piston skirts break off and end up places you don't want them, or even worse. There are a few ways you can lower compression. The easiest way without tearing your motor back down, would be to put a set of heads on that have bigger combustion chambers. This can take .8 to 1.5 away from your compression ratio if you are running a regular flat top piston. Another way of lowering your compression is to run a dished piston. Dished pistons have a place on top of them that has metal removed like a bowl or dish shape. Your piston volume is measured in cc's. A flat top piston is 0. A dished piston will have a plus in front of the cc number or it will be a plain number. A dome or pop-up piston will have a minus in front of the cc number. These are what you want if you want higher compression. Now a pop-up piston looks awesome and will really make a motor scream with compression and a lot of guys buy them simply because they look cool. That's fine if they are going to run high octane fuel but most end up with a motor they can't even run because fuel is too expensive or they end up destroying it because of detonation. Most guys that want to run pump gas, I will tell them that a 5 cc piston will keep them safe with a stroker. Head gasket thickness is an issue too but not a really big one. I mean, if you were right on the threshold of being a few tiny points over your target compression ratio, then putting a thicker head gasket on would definitely help you out. Basically in a simple way of explaining, anything that is going to take more air space away when the piston is at tdc, is going to give you more compression. Anything that adds more air space is going to take away from compression. Another factor is how your block deck has or hasn't been milled, and whether your heads have been shaved/milled down. Hope this helps

[@MylesZ06]

I do run 93 pump, actually! My motor is a 383 from Golen. Im not sure how they set the motor up, but it is a bullet-proof build. Anyone that has purchased that package is in love and can abuse it! I think what Golen said, is that they did a lot with timing in the engine, so that helps with the extreme compression ratio. Im not too sure man. But it is recommended we run on 93 octane. If you have any ideas or more explanations, all would be helpful. Thank you!

[@DandGBears]

How on earth can Mazda's new line of four cylinder engines run 13 to 1 compression ratio on pump gas? Mind blown.

[@DandGBears]

87 octane on 13 to 1 compression ratio I should say. Nuts!

[@Myvintageiron7512]

Some of the newer cars with OBD2 control can run much higher compression with computer control along with advanced fuel injection and head and port design they use knock sensors and variable cam timing to make it work with most engines it is not possable

[@DandGBears]

Dang! Thank you!

[@DandGBears]

As a side note I wonder how much it would cost to rebuild one of those new Mazda heads. Then you can tell your favorite customer how lucky he actually was with his price lol!

[@aaronbuster1989]

A lot of it is the scavenging of the exhaust at the RPM knock occurs. If you can pull out more of the residual exhaust, the next cycle's temperature will be reduced resulting in less chance of knock. Direct injection also helps in cooling the intake charge. PFI also cools the charge, but some of the heat the gasoline absorbs is from the walls of the intake manifold. If sprayed correctly, DI shouldn't contact any surfaces, so a higher percentage of the heat absorbed is from the air charge (cooler temps before compression = less knock). I also read an SAE paper on the divot in the top of the piston, but I forgot how it affects knock. I know it benefits combustion stability since the flame kernel has a spherical dish to grow in.

[@CompetitorsEdge22]

first off love what your doing and awesome videos! I see that the compression ratio calc. you are using doesn't take into consideration gasket bore? i like to use www.uempistons.com/index.php?main_page=calculators&type=comp&zenid=e53f9ef502be8e8714b38b13d8ffb987 plus then I can plug in my cam timing and figure out what kind of dynamic compression ratio i will be running, what are your thoughts on this?

[@DingDangg]

When is your next video?

[@Myvintageiron7512]

I know its been a while I have allot of things going on but I assure you the 383 build will get done you should see more on this towards the end of sept thanks

[@beck2557]

Myvintageiron7512 great video, question though, where did you get the hat you're wearing in this video, if you remember that is? I love me my chevy trucks lol

[@coalminefarms222]

How do I run 12.7:1 on pump gas

[@Myvintageiron7512]

you don't

[@JG-kv4oi]

You put a cam in it that closes the intake valve at 100 degrees ABDC so your dynamic CR is 8.0 to 1

[@fishydubsfishing6516]

I get my fuel ⛽️ at the airport

[@donrutter6550]

worlds fastest Chevy engine, a sb 377, 350 stroked 1/4" 5.64 in the 1/4 www.hotrod.com/articles/inside-the-quickest-small-block-chevy-engine-ever-built/