Quench action - money saving power adder

[@anthonylorek8847]

I recently built a Dart SHP 400 block following DV's recommendations from his how to SBC budget build book. I went with every upgrade for my performance street engine build, too many to list but a few. Scat F-43 lite weight internally balanced stroker crank, Scat 6" H-beam stroker rods and forged/coated Mahle flat-top pistons .005" in the hole, block decked 9" and I initially installed .030" gaskets. Cranking psi came in at 185psi at 8500' elevation, should be 200ish at sea level. I swapped in a .011" steel shim gasket and sprayed a copper coating to seal surface imperfections, (used 64cc Edelbrock Performer heads I ported and polished following DV's head porting book) to prevent galvanic corrosion between the iron block, stainless steel shim and aluminum heads. Micrometer reading was .013" and cranking psi is at 200psi at 8500'. The cam is DV's Hi-Po grind, nitride coated 268 hydraulic flat tappet, 105 LSA, 1.65:1 roller rockers and beehive springs and lots more. Very pleased!

[@6426yy]

Where did you find an .011" gasket?

[@anthonylorek8847]

It was back in 2021-22, but it was Summit Racing. I just looked it up and the closest they have now is a Felpro .015" shim, 4.100" bore. My engine has a 4.125" bore and the gasket is also 4.100" so it's .0125" smaller all around. I was a little concerned at first but since the piston is .005" down, all seems fine. Orient the head gasket so the stamped high side is towards the block, and as it gets compressed the inner edge pressed into the head and not down towards the piston.I recall the block was decked 9.005". I'm between 11.5 and 11.75:1 CR. ARP's best rod bolts, ARP head studs and ARP hardware thru-out.

[@mikkokuorttinen3113]

Thank you Mr.Vizard for the explanations and the illustrative chart! I like all and any torque gains due to choosing part more wisely

[@kevinclancy.]

Great video. I am amazed at what a proper quench and combustion chamber can do. I run a 355 sbc on the street with iron Bowtie heads (64cc closed chamber design), a 0.015 steel shim head gasket, small domed pistons 0.025 in the hole, and my static compression ratio is 11.6:1, dynamic is 9.9:1, and I run 39° of total timing, small solid roller cam with 234 I and 242 E duration (@0.050 lift) 108° LSA, and I installed it advanced 3° so my intake valve closes at 39° ABDC (0.050). So my quench is 0.040 and I run 93 unleaded pump gas- no ping, no kickback on hot restarts, it's great!

[@jmflournoy386]

sounds about right for .040 quench

[@krispinlihme529]

I love the old school and highly relevant tech advice. This type of knowledge is relevant and invaluable.

[@KentuckyFriedFixes]

Great stuff David. I really enjoy the discussion about the Small Block Chevy and engine build theory. I like the way you think. I've tried experimenting to the extremes on small engines because it's cheaper to build the single cylinder vs a V-8, though I have built my share of SBC engines over the years as well (some based on small engine experiments). My best running engines have always been the ones with the piston above deck at TDC. The tightest quench I've been able to make work is .025 with all billet components. I tried less quench but ended up creating hot spots in the cylinder and burning thru head gaskets. Those failures led me to remove the flat areas of the cylinder head and gently round them into the combustion chamber. Then I figured something out. I think that when the piston is above deck there's a better heat transfer during the valve overlap. With a longer rod and increased piston dwell at TDC, a piston that is above deck will transfer heat better than one sitting down the hole at TDC. I've done some other experiments based on some of Smokey Yunick's theory on heat transfer. One included a stainless steel cap on the top of a piston. (It didn't stay attached and so that experiment failed before I could determine if there was any benefit or not, LOL!) but the idea is sound IMO. This is turning out to be a long comment, sorry.

[@SnappingTurtle444]

Thanks Mr. DV ... Really enjoy the wisdom and storytelling - SBC 🐢💯

[@atheplummer]

A good friend of mine, just recently passed away, he built many Brigg's & Stratton garden tractor pulling engines. He eliminated piston rock at TDC, by milling 3/8" reliefs in the piston skirts, then stuffed Delren 'buttons' as he called them, to tighten up the skirt in the bore, keeping it square, without causing any wear to the piston skirt. Only thing necessary to pay attention to is skirt collapsing under specific conditions.

[@theshed8802]

I agree with absolutely everything that you have said in this episode David. I have mentioned before on other videos that you have done that on the Cleveland's that I used to build a lot of, i prioritised quench over almost all other considerations, in order to maximise mixture motion towards the spark plug. Cleveland's are notorious for no swirl, but my engines never lacked low end torque with closed chamber heads. I was trying to maximise the violence in the mixture movement to substitute for the lack of swirl, even though I didn't even know about the lack of swirl back in the early 80's. I just knew that if I ran the pistons close enough to the head that the gas movement eroded the machining marks off the top of the piston crowns, life just kept getting better. Great stuff David. Regards Greg

[@NotSure723]

Your colorful diagrams are just fine. Screw the haters.

[@trailerparkcryptoking5213]

My street BBC has 9.7:1 CR with flat tops, closed chamber heads, 0.028” Cometic MLS head gaskets and 0.010” in the hole for 0.038” squish. I run a Straub spec’ed Clay Smith HR cam 221/235 @0.050” on a 109 LSA, air gap intake, 3310 Holley, 40* total timing....it is an absolute torque monster and rips from idle to 6000 RPM.

[@RonaldLewis-py6yt]

I'm on the fence I can go BBC or 383 SBC I wonder about your mileage I gotta 91 4wd 3/4 ton and I need to drive a couple days a week ,do you run a aftermarket torque convertor! Thanks

[@trailerparkcryptoking5213]

@@RonaldLewis-py6yt I run a Freakshow stall converter 3000 stall. With the low end torque I only need a 2000 stall, but don’t run a factory converter with big torque, it balloons the converter and knocks the thrust washer off the crankshaft! Gas mileage is not good, probably 8-9 not getting on it, wish I had overdrive tranny and 3.43 gearing instead of 3.73

[@CULT539]

It’s called QUENCH not SQUISH. God almighty why people call it this is mind boggling.

[@trailerparkcryptoking5213]

@@CULT539 SQUISH SQUISH SQUISH SQUISHY and SQUISHY SQUISH .....!!! Got a low compression, small cam, factory cast iron heads, dual plane intake, vacuum secondary carb and old HEI distributor kicking out 600 lb*ft of torque on 87 octane and your obsessed with a word? You don’t know jack💩 or you would be impressed with a mild tune making this kind of torque and pushing 4500 lbs into the 11’s.

[@jmflournoy386]

Exactly what we did in 68 when chrysler went to open chamber heads. First we welded up the chambers to give quench pads. Then after custom forged pistons worked with what became the KB quench dome pistons. With the right cam EGT was reduced by 800 degrees Lots of dyno time We set up a PER to rebuild warranty HD Mopar engines

[@recoilrob324]

In the motorcycle world...we've found that 1mm squish is about optimum. If you go much tighter you not only start to run the risk of piston contacting the head, but also the squish velocity increases the tighter you make it. This can start to strip the boundary layer off of the head and piston thus exposing them more to the flame and increasing their temperatures. Years ago I ran RD-400 Yamaha engines so tight the overbore stamping could be read in the carbon on the head....and lost a bunch of pistons to detonation before I finally figured out that I had them too tight. Shoot for .039" and you'll get good results. Squish...or rather lack of it is why the Hemi with open chambers doesn't do well at low rpm due to the charge taking too long to burn because of stagnation. That's why aircraft engines using this design also have dual plugs....makes for quicker fuel burn lighting it in two places as well as gaining redundancy. Modern intake systems and head design induces swirl which can energize the charge velocity and spread the flame more effectively which is what squish does as well. The object is to get all the fuel to burn in as short a time period as possible needing as little timing advance. Open Chamber Big Blocks often need 45+ degrees of lead....where modern high swirl chambers make best power in the low 20's.

[@GTE_Channel]

On my 250cc 2stroke track bikes we ran 0.6mm. On the street we ran 0.8. It does rewuire building the crank etc with tight tolerances.

[@ryandeweese363]

Thank you for taking the time and sharing your acquired knowledge and "hidden horsepower" with us!! Look forward to being able to apply learned lessons into mine and others builds!

[@WalkerSmallEnginePerformance]

I do small engines and I always put the piston even with the deck whenever possible and achieve .030 quench with the correct head gasket.

[@donaldhalls2189]

Thanks for sharing, all the best to you and your loved ones

[@shotsrodder]

Great video 👍

[@timmcooper294]

Years ago built a mongrel 311 cu. in. Chevrolet straight six, based on a lot of what I learned reading D.V. books back in the day. 11.1:1 calculated mechanical compression ratio, 220 lbs cranking compression, .025" quench clearance. That engine ran a happy life on 92 octane unleaded, was incredibly responsive and snappy, just a great combo. Years later it dropped the head off an exhaust valve, destroying the block, ect. Replaced it with a 6.0 LS rectangle port engine, and was disappointed by the lack of real grunt..... 364 modern cubes did not pull as hard as 311 old school properly built cubes. So the LS is getting a proper build now.... 😁

[@jmflournoy386]

More torque down low with the g, my 250 6 was similar I used v8 pistons and cut a "d" dish in them

[@timmcooper294]

@@jmflournoy386 My piston of choice was a KB hypereutectic flat top, no dish or reliefs (Ford stroker application) and a light weight low tension ring pack. Turned down the counterweights on a 292 crank to clear, with 6" rods in a 250 block half filled with HardBlok and bored to 4.000". To feed 311 cubes, did a lot of surgery to the stock Iron head in my mill and ran 2.050" intake, 1.590" exhaust with 8MM stems. Probably should have bucked up for a Sissell aluminum head, but it was a scienced out engine that ran really good for years. Never had overheating problems in 100 degree Cali weather, the half fill kept the cylinder walls really stable with no heating trade off.

[@jmflournoy386]

@@timmcooper294 Wow 292 crank in a 250 block only done a few times AFIK Sissell was a good friend of mine. He was a firemnan and had just had a physical at the hospital and dropped dead while leaving. RIP He had a hydrallic (CNC) that would copy a known head and ports to do most of the work. that's how he did his lump ports after brazing up the ports which works better than inserts. I used one of his heads on my build. Mike Kerby is still carrying on AFIK, better check he has one of my heads...

[@timmcooper294]

@@jmflournoy386 Sissell really knew his stuff.... We lost him way too early....Too few people on this earth have the ability to think....that's why I appreciate DV so much... I looked at what he did to his lump ported heads and did my own version, using the smaller stem valves and venturi porting along with the lump ports. The forged steel 292 crank I used required the counterweights turned down for piston clearance at BDC, and I wanted to reduce weight as well. The rotating assembly was very different from what the "experts" were doing, as I didn't like the tall, old school forged pistons they were clinging to.... I wanted light weight parts to reduce the stress and harmonics, having lost a flywheel off the back of a 292 !! I think the 6" rods really helped this "292 crank in a 250 block" work well. I also knew that the tight bore clearance afforded by the hypereutectic pistons meant lower friction and stress on the cylinder walls I used a light flywheel and clutch, and a light weight 250 harmonic damper. I think the use of light weight components on either end of the crank really helped with the harmonics problem. Never had any overheating, detonation or bore wear issues with this combination, it was a super fun street engine that I ran the crap out of for years, and I'd recommend this combo to anyone who wants to build a "sleeper" Chevy six.

[@stevenhobbs709]

Thank you David, quench is fascinating and I look forward to more on the subject. I hope you’ll touch on angled, grooved and multiple quench pads. Incidentally as someone nowhere near the Atlantic I always heard “squish band” referencing 2 stroke and quench in relation to 4 stroke engines.

[@79beans347]

Very good video Dv. I still want those heads

[@thomasnikolovski3258]

Mr Vizard I have been to your seminar here in Sydney (at Steve and Aaron Hamburg's APM facility) and combined with reading many of your books I have learnt so much, especially about "the brain" of the engine. I am amazed how some people do not seem to grasp what you are telling us. I do have , what I feel, is a good analogy to explain the part played by overlap and would love to run it past you for your comment, so if you would care to hear it please let me know. Take care, thank you so much and keep up the great content.

[@The340king]

I recently rebuilt an engine that has reportedly performed well at a big race. When I pulled it apart I was shocked to find the pistons 0.007" down the bore with a 0.076" head gasket. That's 0.083" of quench. The only advantage they may have gained was the unshrouding of the valve at low lift where the quench pad on the head used to protrude beyond the valve seat. These heads were milled down to the 30° cut on the seat. I felt the cfm gains from milling weren't enough to offset the loss of the quench. Unfortunately, it wasn't known until after tear down. We didn't have a before dyno number to compare to.

[@approachingtarget.4503]

Massive turbo applications gain from softened chambers. The quench pad also has a lot to do with the approach to the valve seats. Quench is more than just one area of the cylinder head. Keeping the compression tight around the exhaust valve, helps the exhaust empty during the event. Head gaskets have limits. The thick .045 gaskets cam not withstand the cylinder pressures or heat as long as a thing or o-ring set up. Multiple layer steal gaskets should replace the paper variations in most cases. David....I think you could have included the reasons the clearances are needed. The heat expansion and bearing clearances all add up. Place a piston in the TDC position using a dial indicator as you normally do. Make sure little oil or assembly lube is filling clearances. No apply pressure to the bottom of the piston. You will gain about .007 on your indicator. That is observed in its stationary state. Now the gross growth a running engine creates is easily double that. ROD materials will also grow. The stretch in head bolts, and .005 bearing clearances all add up. On a typical wedge engine. A clearance less that .015 will evacuate the pad of compression gasses. Pre Ignition will happen, and the loss of pressure will not help cushion the piston from hitting the head. .018-.022 is prime for small block clearances. Over .035 makes a lazy pad area.

[@user-hc5of8xk3r]

I always enjoy listening and learning from a master like this, built some rods in my days, but you never know what you don't know until you know. Thanks !

[@billlittle4285]

Excellent video, your number one in my book David, thanks!!

[@duanedabney9420]

I took a standard bore 350 with 4 relief flat tops, which were .022 in the hole. Added a set of 5.7 vortec heads along with some .015 steel shims and really woke the Ol girl up. I also threw in a L79 replica cam in that I had. Granted the cam probably wasn’t the best choice but it was there and why not. Nowhere near the same engine!! Total quench ended up being .037.

[@CCerwin]

Thank you 🙏 for sharing and not only taking the wisdom to the after life. The young kids and many will need to know this when it comes back around again. Almost everything comes back around at least twice and sometimes many more

[@jfv65]

I experimented with this on a Volvo redblock inline4. Quench as tight as i could get it. Not with any stock HG but with a Cometic MLS HG. That (turbo)engine that i also coverted to run on e85 and high boost ran like a scolded cat. Good times!

[@michaelblacktree]

I cringe when people talk about using thicker head gaskets (to reduce compression) for boosted setups. It often ruins the quench, which is counterproductive.

[@ImperatorCaesar22]

AFAIK one good way to reduce compression safely is adjusting cam timing so that the intake valve is open longer, into and during the beginning of the compression stroke, which shortens the compression stroke and ratio, and also as a byproduct may slightly increase efficiency by increasing the Compression-expansion stroke ratio

[@mechticulous8202]

I will keep an eye on that.

[@chippyjohn1]

Yep, and people not using multivalve, dohc and efi. Its crazy

[@pontiac411]

You wouldn't if you understood soft chambers in boosted or nitrous engines, also Pro Stock runs around a 1.5 degree quinch for softening. Tight quench is only beneficial if your trying to run the least octane for your compression.

[@JamesCat-qx6sb]

I agree 👍. I had measurements of. 043 in the hole and a .048 head gasket...someone had put the thick rebuilder gaskets on it in the past. I prepped the heads and block during my rebuild to run. 027 Cometics. Quench isn't still ideal but much improved I think...went from. 091 to. 070..

[@robertwyman1497]

This is great stuff. When talking about squish this small it scares me. A fresh engine, fine an experienced driver fine too. But what of a worn engine with a cooling issue and god forbid a young driver. A word of caution is in order. Smokey suggested .038-.043. .018- .025 wow! "Warning Will Robinson - Danger! Dave you are the best.

[@gordonborsboom7460]

Remember the caveats he gave of limiting RPM to under 7000. Who knows the RPM limit Smokey had in mind.

[@jackbooten2681]

Thanks for your sharing DV

[@tomtaylor6028]

Good stuff, my teacher who taught us engines mentioned a lot of what you said. It took a while to understand that decreasing the quench height though adding compression helped tame detonation by making the mixture more uniform, it took some drawings on a white board but a lesson i never forgot

[@mattsnook1723]

Love your work David! I have followed your ideas on building an LS 6.0, cam selection, heads, etc. Even your exhaust ideas with the pressure wave box. Very pleased, massive torque on the street.

[@joejones4296]

Thank you DV. Can you ask your producer to minimize the annoying "music"?

[@avidcat11]

Going after this on my bbc 454 build. Horsepower through correct machining.

[@dannoyes4493]

Well done. Thank You.

[@richardfehr1838]

If I was king of the world, everyone would call it squish, because that's what Sir Harry Ricardo named it, and I bet you know who he is. For the rest of you, look him up. He pretty much invented the concept, or more accurately, discovered it. During my ME IC engine classes, I was intrigued by the observed flame speed in a quiescent chamber, meaning not much movement of the mixture. The flame speed was deplorably slow, compared to what was needed for it to travel across the chamber. I believe that what squish does is it creates a jet of air/fuel which physically transports the flame through the chamber very quickly. This causes the mixture to burn more completely and doesn't allow the decomposed end gases time required to self-ignite and thus cause spark knock. US engineers call it quench because they thought the cold piston would cool down the ignition that was about to start and create knock, thereby quenching the offending self-ignition. I believe this is a misunderstanding of the physical processes occurring in the chamber and is why I resist calling it quench. The sad part of all this is that when US engineers lowered compression to accept unleaded gasoline and decrease NOx, they converted many engines to open chamber which essentially removed the squish or quench areas in the cylinder heads, resulting in a generation of doggy engines. R.

[@JohnH.-qp6fb]

I had been talked into a spherical dished piston long ago from a known tech man at JE at the time. The feedback they had was the reason it was used at the time. I haven't yet built that engine however, another friend has used this with great power. No, outstanding power. Never hear about them now. Randy was the man at JE at the time.

[@danielfarmer1334]

I always learn some thing from this race engine building legend, he's built more winners than you can shake a stick at, right up there with Smokey ! Thank you David, your always the to go guy in my mind, few can compare, None Ever Better ! Looking forward to video's on 351 small block fords, with Andy, if he's handy , , , , , I'll be watchin' ! I want to build a 4 to 5 hundred horse 351 street and track anvil that will take a heavy right foot, and hold together for date night week ends with a trophy girl or three, take care, thanks !

[@Jerome-t7t]

Thank You David, It was good stuff, easy listening, It goes along with your book that I have read and memorized

[@baitone2889]

Glad to here from you again. Great info.

[@bradroark6036]

Thanks for the good information dave

[@Comet-hn3gm]

Quench is the area that is flat on the head (large or small) and the flat part of the piston that is directly opposite of it. Squish is the distance between the two of them at the closest point. Many potential reasons for a given distance, RPM, piston to bore clearance, piston growth, conecting rod stretch. Etc.

[@mikewillett5076]

Not to mention if a bearing wears excessively or wipes out. The piston could more than just kiss the head.

[@g0fvt]

DV, I understand your explanation and the influence of connecting rod stretch and piston rock. What I am not understanding perhaps is the mechanism behind detonation. It would appear that the instantaneous pressure with a tight squish clearance would be higher. However an opposing factor would seem to be that a flame would not readily propagate between two very close proximity parallel thermally conductive surfaces. (Perhaps akin to the principle of a Davy lamp). Being an Englishman myself too, perhaps now the American term "Quench" is making sense, that the narrow clearance prevents unwanted combustion. Thank you for the work you do, I will continue asking "why" until I fall off the conveyor belt.

[@DanielDeVos-tx2ei]

An other awesome video thank you so much your helping so many with your wisdom

[@phildo39645]

Thanks David Great Stuff Forsure!

[@phildo39645]

Would bbc minimum clearance limits be similar to sbc?

[@davidwood1923]

Thanks for Sharing... Always Enjoy the Information and the Thoughts and Ideas they Produce.

[@gordowg1wg145]

As I think was mentioned, there's a relatively fine line between getting it right, and getting it wrong - and getting it really wrong! There being quite a lot of variation between engines. As I recall, for proper quench - pulling the heat out of the compressing gases trapped between the piston and head, it should be a max'of 30-40 thou', with alloy heads allowing the greater amount. from there, up to around 60-80 thou', not enough heat can be pulled out and detonation of the trapped gases can be a problem, and bigger than that it usually isn't an issue.? Might very well be wrong, though! Some years ago, there was a thing for using slots in the quench area of the head - think they were called Singh slots, or similar - that were supposed to give the compressing gases there an escape route, with the advantage of being able to direct the 'jets' for improved mixing of the charge? Diesel engines usually have, by their nature, flat heads and valves, with a combustion chamber in the middle of the head. In order to get the required swirl, curved, semi-radial grooves were machined into the head and/or block, so the gases pushed by the up-rising piston introduced a swirling action in the cylinder so that, when the fuel was injected, it gave a better burn - especially as it approached the head and the pressures were higher. Something like the Singh (?) slots mentioned above.

[@johnzuggster375]

Thanks David, much love for you and the Gold you give.

[@markcole6475]

I’ve always based my engine builds on .040 quench…..that’s the thickness of most typical head gaskets are ….zero deck and .040 quench have been that magical number for my best performing engines… Ran pump gas on a 354 ci 8.2 deck ford ….11.2 to 1 turning 7000 rpms …engine made north of 550 chp n/a ….ultra snappy throttle response ..

[@jmflournoy386]

I think of quench as two cold surfaces quenching the fire preventing detonation and pre ignition on the area away from the spark plug/ I think of squish as the jet of gas squeezing out of the quench area providing turbulence. With a low compression motor more is better on high compression you can have too much squish (blast) and blow out the fire we also ran into this at 60 lbs boost on alcohol even with low compression and wedge head & d cup piston (like the TRW chevy "turbo" piston) so we cut the quench pad back (I have not tried tapers (yet))

[@jacquelinechellis4036]

Building a 200 cid ford six.. same principles apply. I got flat tops, after mock up assembly i will figure how much to deck. No thin gasket available so this is great info. Thanks for your experience and knowledge.

[@jaan-e]

I've got my hypereutectic flattops 0,5mm out the hole. With the fel-pro head gasket it gets 0,026" - 0,029". Very on the edge.. I won't rev it much over 6k.

[@jacquelinechellis4036]

Very cool​@@jaan-e

[@jayc.9529]

Mike Cook ,in Carson CA. Passed away a couple years ago, "COVID". I worked for him in the early 90s to the late 90s

[@MVPisME383]

Awesome content bloak

[@laszlototh5956]

I would like to know what can be the downside of a quench pad? I saw that there was a tendency to eliminate quench from many combustion chambers by many manufacturers. One example the menufecturer changed from a decent quench to basicly no quench on the same engines newer generations. Is this only due emissions? I even saw quenchless head on a 2 stroke bike of mine. It was a German market restricted version. When I replaced the head with a normal quenched one the bike just came alive. The two heads had nearly identical compression.

[@jmflournoy386]

was non quench pad direct injection otherwise must have been emissions

[@curtislovrak5390]

On my non turbo Volvo redblock, I was running 9.5:1 compression and .044" piston to head clearance with a 231° @.050" cam (V profile). I knew that was too little compression but the machine shop didn't do what I asked them to. I had advanced both cam and ignition timing and I thought the motor was pretty peppy everywhere. Because of the machine shop's incompetence, I had to do another head. The head surface was too rough and the composite gasket never sealed on all 4 cylinders. This time the final number was 10.1:1 compression and .033" piston to head clearance obtained by running an MLS gasket. I returned the cam and ignition timing back to stock, and even then the biggest improvement I feel is off idle. I've advanced the cam again and I'm still not running into detonation with 87, I really think I could've gone to 10.5:1.

[@CK-mf6du]

What are the cam specs at .004-.006 or advertised duration, and what is the lsa of the cam? What is the current displacement and what size valves in the head?

[@CK-mf6du]

Would also need to know bore, stroke, and rod length dimensions. Assuming pump gas.

[@curtislovrak5390]

@@CK-mf6du Duration @.005" is 257°. LSA is 110.5°, I currently have it timed at a 110° intake centerline. 96x80 bore/stroke with a 152mm rod (2316cc), 44x35 valves. I had since thrown in a cam with 242° duration @.005", 212° @ .050", 109.5 LSA to test the limits of compression. It would detonate under moderate load at cruise, but at WOT it was okay on 87 octane, same 0-60 as the larger cam because of how my low stall automatic is geared. 91 it still ran a little funny, way too much cranking PSI to idle smooth, that camshaft with 8.3:1 static compression idles very smooth. I still think I can trim another .015" off the head.

[@CK-mf6du]

@@curtislovrak5390 what rpm range are you aiming for? My math says you would be making hp close to 6200 rpm. 110.5 lsa is close to my calculation, i came up with 109. That's a pretty quick lobe on those cams? I know 9 to 1 dynamic has been tested to work on dyno engines, but I feel like a real world number is 8 to 8.5 for 87 especially. 91 only as good as the tank it's been sitting in for however long.. at 10.5 to 1 static your dynamic goes to 8.69 to 1, I'm sure you know that. Your lsa ratio will also get closer to right the further you go up in compression. So yes I think shaving a little could benefit, but you might get back into some low end spark knock/pinging.

[@CK-mf6du]

@@curtislovrak5390 dynamic compression would have been 8.8 to 1 with that smaller cam. Too much in my opinion for 87 for sure. Perhaps a polished chamber could help but I have no data to support said claim. I appreciate you giving me the specs. Just used vizards 128 formula to derive the lsa, and a simple chart referencing based on known overlaps, and associated rpm ranges. Also tweaked that number referencing your displacement to intake valve size. Curious to know if that 6200 rpm peak is in the ballpark right now?

[@JohnH.-qp6fb]

Years ago, I was trusting my salesman Randy in those days, to use a spherical dish piston rather than a chamber matching decompressed piston. He had claimed this was an improvement over the other. Yet to be built, I've been nervous about this until another builder went with this on his stroker Chevs. The Dart heads of course, were not served much quench but the power was outstanding with such a wrong way to do it approach. 12:5-1 ratio.

[@rodneysteffen6376]

At about 17:20, DV says "it's a powder metallurgy rod, which is a lot better than the forged rod that came previously". How so???

[@billymanilli]

They are. More uniform grain structure for one... but there are other advantages, as well... easily found with a bit of research

[@StefanRügamer]

Great Viedeo D.V. My 283 SBC will her a few extra horses with those power secrets to get an efficient quench area.

[@deanstevenson6527]

On the Speed Talk forum, a great discussion on the SAE compression linear regression sliding scale. It is a percentage increase: From 6:1 to 7:1 is a 16.6% increase in compression From 17:1 to 18:1 is a 5.8% increase in compression CR 6 = 46.61% thermal effic CR 7 = 49.64% CR 17 = 64.33% CR 18 = 65.12% Going from a CR of 6 to 7 increases thermal efficiency by 3.03% Going from a CR of 17 to 18 increases thermal effic by 0.79%. But an increase in CR is always able to give a definite hp and lb-ft increase.

[@dondotterer24]

What clearance in a n/A 421 Small block Chevy. Aluminum block and heads H beam rods forged pistons under 7000 rpm? Approx 11.00 compresion Thanks again for the great videos!

[@lukesimeon5756]

Great info DV thanks

[@deancrawford2577]

Keith Black illustrated this point over 40 years ago, I still have those old piston catalogues. Fast forward to present day where forced induction is more common and the same/similar rules apply and we can run higher compression and boost and the engines don't grenade themselves.

[@salvatorehayes2753]

It's Insane How These Videos Coincidentally Come Out Perfectly With The Stages Of My Engine Build. I've Got A Little 3.8L V6 Turbo Engine. Engine Is Apart After A Lifter Failure (my lifter preload wasn't correct on my fixed position rocker engine) It's A Hydrolic Roller. After Measuring Each Valve I've Got To Correct Pushrod Lengths Made A For Correct Lifter Preload For Each Valve. Long Story Short The Engine Had To Come Apart From The Lifter Desbirs, The Cylinder Closest To The Failed Lifter Got Scored. Block Is Needing To Be Rebored So It's New Piston Time. I Was Running Dished 19.5 cc Pistons Which Put The Compression Ratio Around 8.0 With My Combination. I've Spec'ed Out Some JE Pistons With Same Compression Height But In A Flat Top Piston Which Puts My Compression Ratio Right Around 9.9. I Was Originally Going To Install The Same 8.0 Pistons But In A .020" Over Size However I Wanted To Test Out The Nickel Plated Crown. I Had Ceramic Coated Crowns Before And The Only Thing I Didn't Like Was The Slight Carbon Build Up After About 20,000 Miles Daily Driven. I Figured The Super Smooth Finish Of The Nickel Plating Would Give The Carbon Less Of A Chance To Hang On To The Crown (plus the ring groove "anodizing effect" the nickel plating also provides). Diamond Does Not Do Nickel Plating, So I Reached Out To JE. Custom Pistons Had To Be Completely Engineered From The Ground Up For The Plating. Since I Had The Engine Apart And Pistons Will Be Ground Up I Figured I Go With The Highest Compression Ratio While Maintaining Same PTV Clearance On Same Compression Height. This Came Out To Be The 9.9 CR With A Flat Top. The Piston Set Ran Me $2,000 For 6. I'm Very Dedicated To This Odd Ball Engine As You Can See. The 9.9 CR Ratio With My Given Engine Combination Is Really Close To The Rough Theoretical Optimal LSA Of 110°. I Needed About A 108° For The 8.0CR But Comp Cams Wouldn't Grind Me Tighter Than 110°. With The Need For New Pistons I Saw An Opportunity To: -Test Out Higher Compression -Get The Engine Combo More Focused For The Camshaft Limitation. Engine Removal And Installation Takes Me 40 OCD Hours To Do So I Try And Make The Most Of My Repairs So It Feels Like It's Not Time Wasted But Rather Personal R&D To Add To My Novice Experience Of Engine Building. My Quench Seems To Be In The Sweet Spot. Piston Protrusion On This Engine Is About .032". I Say "About" Because Its Actually Kind Of Hard To Measure When The Piston Rocks At TDC On Top Of Having Offset Wrist Pins. My Head Gasket Is .063" Putting Quench Around .031". The Engine Is A Daily Driver And Only Shifts At At 5800 RPM. It's A 4 Speed 2.93 Gearing So Average Torque Production Is Crucial For Me. Intake Runner Length Has Been Tested And Is Perfect For My Operating Range. Turbo Us Also Sized Accordingly (but was for 8.0CR). GTX3582R China Turbo With A .82AR Turbine Housing. I Used To Run A .63 AR Housing On Stock Camshaft. I Run A Small Turbo Because I Also Live At High Elevation Of 7,000 Ft. Camshaft Is A 210/212 Putting My Power Where It Need To Be For My Application. This Compression Ratio Change For 8 To Nearly 10 Is Likely Going To Be The Last Peice Of The Puzzle For My Build. I Do Anticipate I Might Have To Change The Turbine Housing To A .96AR With This Jump In Compression Since Spool Is Probably Going To Be "Too Good".

[@ElvinLeadfoot]

Stock Styled Engines:) Economical Builds There’s fun and enjoyment in that because of daily drive ability, cost, and time. Not to mention all of the technical aspects of having a body and suspension that can handle an engine like your beastly 383 SBC Or that 632cid you and Terry built:) Thank You King Dave I’m going to joke you at your instructional seminar. Referring to you as (Lord) Thank You My Lord Legend = Lord now:)

[@Grooty79]

I run as tight as possible on all my builds, I find I can run more compression on pump fuel, there is no noticeable negatives running tight quench on Na engines in my opinion ,

[@gearsandbeers9100]

Quench does add power. that magic range I found on type 1 boxer 1 5/8 primary headers ,flat top pistons ,60cc head combustion chambers , 9 to 1 CR . 272 D,4.2L 108 LC Cam with twin dual choke carbs is 0.0028" to 0.0045" piston to head clearance @ TDC , went to the high side . Noticeable difference in sound at idle and increased torque. Great video David.

[@jeffreydurham5342]

Are your decimal points off by 1? Two to four thousandths seems a little too close to me.

[@jacksonbermingham2168]

dan gurney/the gurney flap on the wings was probably one of the most influential aero dynamic design there has ever been in racing

[@patrickmazzone9066]

excellent Content thanks for sharing

[@OgamiItto70]

"Squench" and "quish" sound dirty. I'm looking forward to the upcoming videos on these fluid/thermodynamic issues inside an engine. All this stuff is endlessly fascinating. Thanks for sharing.

[@1OMEGA111]

Get your mind out of the gutter, the terminology is old old old

[@OgamiItto70]

@@1OMEGA111 You _never_ let me have any fun!

[@rogerstill719]

A 318 is a prime example of too much Deck height/ to little quench

[@jamest.5001]

I heard rumors of a monster in the forest. Called the sashQuench! 😮 haha.. have a awesome day!

[@robertheymann5906]

Thanks DV!

[@flinch622]

This does confirm that most off the shelf pistons have compression height on the low side. What I recall running across over the years is that 0.045" to 0.075" quench is no mans land, and don't build there? As for Iskanderian's work, things have stood up well over time - is it the 201271 cam recalled here? 270/221 duration on 108 with 0.465" lift.

[@markcordial4938]

Thank you DV

[@bcbloc02]

Controlling the burn of the fuel is so important but so many people totally overlook that.

[@cedricwilson2055]

Think of all the power lost by not recurving the distributor alone.

[@overbuiltautomotive1299]

good stuff DV

[@scottworelds2933]

On really high boost, the application with high rpm quench can increase detonation sensitivity, which is the opposite of what it is for. The reason is that density increases too quickly in that area.

[@luckyPiston]

heat is being generated in the compression process there, ya left that part out , Lol

[@johnelliott7375]

As always thank you for the help

[@everydayirace]

How did you find out which torque gain was due to compression and which one due to quench ?

[@TheMajictech]

10,000 dyno pulls

[@Bristolcentaurus]

its calculated by looking at the measured total gain then calculating the gain due to compression increase subtract that from the total what's left over is due to quench

[@everydayirace]

@@Bristolcentaurus thank you.

[@robertwyman1497]

Your 'limiting rpm' comment was covered by my 'young driver' statement'. Guess I could have stated it differently. My point was a warning could have been made because the potential catastrophic damage as the engine wears. 10:27

[@Xxjoker21xX]

Im Building a 337 AKA 327 60 over with almost this exact setup Vortec style Aluminum cylinder head 64cc chamber 2.02int 1.60exh, Performer RPM Cam lifters and Springs Intake and Carb .020 head gasket.. It will be in my Fishing Truck 84 S10 Sport EX cab short.. Mid length header

[@justinschmidt9180]

Great video ! Thank you again for the tech. Is it possible for you to give us a example of how to figure out the correct duration an engine needs. I have your book but that section is very vague as is the section on how to find the correct overlap. The book gives a chart but never tells you if its per valve or total. IE. 45 degrees overlap . Is that 22.5 per valve or 45 per valve

[@b_hall]

Its per valve.

[@alleyoop1234]

I recently aquired a free low mileage rebuilt 400(+ ,060") SBC with around .070" clearance with the thick head gaskets, out of a motorhome. Upon removing the heads, I found it has low compression dished pistons with NO quench pad. A few of the pistons also have chunks of the top ring lands detonated out of it! Go figure..

[@luckyPiston]

Tragedy there or should i say travisty is that someone had that motor apart and didnt make it a better engine

[@JeremyFrazelle-or1mt]

DV. Could you touch on the subject of calculating crank deflection please .

[@blueyhis.zarsoff1147]

We all want to see the 318 running on the dyno

[@stuartwall8212]

If an open chamber is shallow enough to create a 10.5:1, Do you think it would it become detonation resistant? Iron heads, canted valves, 4" bore. If the piston (flat top) were .035 away from the spark plug strap, would the flame kernel be touching the ceiling of the chamber and the top of the piston at the same time and spread out across, up, and down the chamber with a push rather than a smack? Somebody around here must have an idea about it.

[@jmflournoy386]

NO open chamber will always be sensitive on side away from the plug. read the burn pattern on your piston tops, will run good with high octane (race) gas like in super stock but not street

[@randywl8925]

Ah, i showed up late to the party again. I'll start at the beginning. Its slways good. 👍

[@vaghol]

Thank you. Very informative

[@davidphillips3953]

So high end engine builders actually reduce quench or make a 4 degree (or some other degree) taper "chamber softening" on it to reduce pumping loss as the two flat surfaces pull apart at very high speed... curious how we're supposed to know witch one is more beneficial for our combo? Any examples of back to back testing of such things?

[@vincebaxter6127]

I may be wrong, but i believe some builders soften" the chambers, or angle the quench pads because they are running aluminum rods that will stretch at RPM. So they have gone to chamber softening as a means of reducing possible detonation.

[@mylanmiller9656]

David how much can be Machined from the top of the block on a ford 400 engine and still have a safe deck strength.

[@Jack-ns5mn]

Always wondered why many stock Chrysler engines have the pistons so low in the bore. Quench would be terrible.

[@richardfehr1838]

In 1968 Chrysler engineers changed combustion chamber shapes from closed to open and basically eliminated any chance of squish. This was a common mistake of the time. They found that they could adjust the compression ratio any way they wanted simply by moving the wristpin up or down in the piston body. This was important for Chrysler because as the smallest of the Big Three, they had the least amount of money to make major changes in production engines. With no squish it didn't matter what the distance was between the piston and the head and they could set compression as they liked. The worst examples had pistons around 0.180" down in the bore.

[@Jack-ns5mn]

@@richardfehr1838 Seems to me somebody made a set of domed quench pistons that would work with the open chambers to produce some quench.

[@richardfehr1838]

@@Jack-ns5mn Right you are! Keith Black (KB-Silvolite) has shelf stock pistons for Mopars and Tim Meyer has custom KB pistons made for Ford Cleveland open chamber heads. Of course, you can have a custom piston produced to any shape you choose.

[@vincebaxter6127]

Last Gen2 LT1 (all forged) 383 i built was kept to .034" of quench. decks were milled to set Pistons .07" down in the bores with .027" head gaskets. Many say .040" is the tightest you want to go, i dissagree.

[@Johns51]

Set the quench first then your compression

[@anthonyjaparks]

What component in an engine, limits it to its maximum RPM. eg. cam; heads; crank; valve train? Thank you

[@stevenbean9706]

your weakest link always limits you pushrods and fastners always break . ive been sending my stuff to be cryogenically treated and had much much better luck myself

[@natez0690]

Usually valve float is the limiting RPM factor on a pushrod V8. If you’ve ever driven a really tired motor with super old or original valve springs, and the thing stops pulling at 5,000 RPM when it used to pull all the way to 6,000, you’ll know. Old springs don’t have the same force that they used to, the valve starts bouncing, you loose compression and therefore power.

[@thomashodges6104]

Do you still port customers heads?? I have a 75 Triumph Spitfire 1500cc. I would like the head ported. Current motor configuration. Board 30 over flat top. 1.65 roller rockers. Kent road cam. Alm fly wheel. Weber down draft. Header.

[@AmirPomen]

0.03inch / 0.7mm d3ck is what i usually applies to race engine that was fuel limited (91 aki limited class usually)

[@joejoejoejoejoejoe4391]

There was some F1 engine, Coventry Climax possibly, and they found one engine dynoe more HP than it should, they stripped it, and found the piston was hitting the head, so they increased the clearance, and all was back to normal, why they did test the engine a full race distance to see if it would last, I don't know.

[@jacksonbermingham2168]

Ben alameda racing KZbin channel does a good video on quench. highly recommend

[@jacksonbermingham2168]

he even shows pistons that have been ran and differences between quench burn patterns on the piston

[@TheMajictech]

Benny is the bomb!

[@paul44235]

Ben is my favorite engine guy on the tube. He is also a Ford guy, so double win!

[@SteveMurray-z1w]

I just posted a comment linking the compression video by Ben, right before seeing your comment

[@trailerparkcryptoking5213]

Ben’s video is great!

[@douglash3129]

Thank You David!

[@larryfernow4071]

What kind of sealer do you recommend for the steel shim gaskets

[@Comet-hn3gm]

Copper coat

[@JustinMorrisV82]

If they are coated nothing

[@anthonylorek8847]

Get some copper spray in a can. I used it on my .011" shim gasket and all good.