Interesting information. Cool video.

The part he left out isn't the minor bump in compression. It's the effect tight quinch has on detonation and between .060 and about .100 is the most prone to detonation. Sbc's ran .060 and low 8:1 compression to prevent detonation on cheap gas. By tightening quinch to less than .045 it allows you to run higher compression with the same gas without detonation. It also helps mix the fuel mixture in the chamber. I suspect that tight quinch helps prevent detonation by not allowing fuel to sit on the hot spots at the edge of the chamber or possibly creating slightly lower pressure in the quinch areas.

@flinch622

11 ай бұрын

As I understand it, quench ends near 0.060". Somebody out there is smarter than me and can probably prove that wrong, I suspect [science does that]. A proper cylinder head bowl/chamber combo provides swirl on filling, but its quench that adds a soft roll motion to the compressed air/fuel mix right near spark to help flame front perform better. A lazy flame front will not burn as efficiently, plus peak cylinder pressure will be a little off.

My lq9 after being decked had a deck clearance of -0.018 which is 18 thou out of the hole. I was set on ordering a .040 head gasket. Had I done that my quench would have been 0.022 quench which would have caused the piston to smack the surface of the head at high rpm (huge issue!). Im glad I double checked and went back to really understand this. It saved me a lot of headache and my pocket thanks me for it.

@muftifaizan1964

4 ай бұрын

I was 25 thou overdeck and used .40 gasket. Rev limit 6500. No issues . 1.6L sohc

I did a super late model engine and when I freshened it up after a season the pins were loose and I could see microscopic marks on the tops of the pistons. I figured I had too little quench space and got the pistons pin holes resized and .003 bigger pins and a .003 thicker head gasket and got the quench to where it should have been. I was lucky it didn't destroy the engine and could be fixed.

some good shit!! love these tech tips. big help in building my little 5.3

Just for kicks, one observation: people always measure piston vs deck with the engine right side up. I do. So... you're "zero decked"? Turn that puppy upside down and see how many tenths out of the hole you are. 5, 8, 11...more? - stacked bearing clearances will show themselves. And we haven't gotten into crank flex, rod stretch, or thermal expansion for a running engine yet. This is why most stop at 0.038" quench when its possible to reach for 0.035".

7👍's up SDPC thanks again for taking us all alone with you

Awsome info thank u i started out on genone small blocks also thank u u guys are awsome!!!

My ls3 mesured .007 out of the hole Thanks for the great lesson

A trend in higher performance applications is to reduce quench. Pro Stock and Comp eliminator have found that they make more power, have a larger tuning window, and less detonation issues when quench is reduced. Softened chambers are being used for this...

@flappingflight8537

Жыл бұрын

I didn’t get it with this “ softening “ . On one side you try to make the quench as small as possible and on the other , in the same time you increase it with the “ softening” of the quench surface of the head . Also , looks like they apply softening mostly to high boosted engines heads .

And if you run that .015 thick head gasket, the best way to get it to seal is to deck the block...which means you can lose that zero deck. Plus the Gen One block uses five bolts around the cylinder bore to seal, the LS uses four bolts.

On Gen. 1 SBC's I have the machinist deck the blocks so the pistons will be down .010" in the hole and I run a .030" thick head gasket. Never built a LT1 or LS motors.

Nice

SBC I am building has .020 at TDC and .015 head gasket. Total quench is .035 I would not go any lower than.035

I run a 15 tho to 65 tho it depends on rod, bore size, bearing clearance bore size.... its completely different for every different engine and where it has to be used

Safe is to factory specs! Factory tolerances need the extra wiggle room. A after market pc with proper machining will benefit drastically with a .030 gap on wedge style chambers. But realistically...l.s. platforms builders are using factory clearances." Play it safe" is for those guys.

What if you run the piston 5 out of the bore on a 383 6in. rod ?

I have a 406 sbc and for some reason my piston to deck clearance is .053. So I end up with .075+. So I need new pistons?

Steel rod .035 safe .030 .028 close ran .035 not problems on 7500 rpm sbc 550 to 600 Hp bearings look great could have reused on rebuild up grade .035 safe if rods hit then you are ready blown up

How much Quench do you recommend for a boosted forged LS?

Factory small and big block chevy's came with steel shim gaskets.

@adamarndt7617

Жыл бұрын

True smog ERA L82 SBCs came with 0.018” shim gaskets. That doesn’t mean that come rebuild time that the deck surface is still perfectly flat. (My 14.4k mile L82 had some high spots on the deck.) The OEM deck finish doesn’t meet the smooth RA values that FELPRO recommends for that 0.015” shim gasket, but they do admit that a spray of copper coat can help deal with minor surface imperfections allowing them to be used.

@joe-hp4nk

Жыл бұрын

@@adamarndt7617 With iron heads and under .003 with a straight edge you're fine. I use permatex super 300 for sealer,

So where can we find the safe guidelines for the L33 5.3 engine? Or are all the LS engines the same as what you said here?

@chickenfoundation9323

2 жыл бұрын

You will have to measure it yourself every block will be different

Race Proven Motor sports has been around for over 16 years. You should take NOTES!!!!

Quench,, Extinguish or put out a fire Use squeeze

Fastest engine we had on a spec engine was running the piston in to the head.

More on the term blueprint your engine

@dog-dx9pd

Жыл бұрын

Blue printing an engine means that you're going back to the exact specifications and everything is done by exact measurements, the piston, cylinder, lifter bore, all bearing clearances, is all clearanced to spec...

@bill2178

Жыл бұрын

thats what i thought

Who is buying these thin gaskets & figuring quench but not measuring piston to deck hight?

@frankrizzo2724

Жыл бұрын

People with an abundance of paper weights.

@billcat1840

6 ай бұрын

I put .027 Cometics on a 5.2 Magnum..had .048 gaskets..I carefully measured my deck height...043 in the hole...no quench whatsoever lol...reduced quench from. 091 to .064

Pump gas and quench is a completely different subject. If your running pump gas, don't squèz the quench. Why, cause I said so.

BlaBlaBla