Im assembling my ls1 back together and was wondering what my compression ratio will be now.
Im running a 243 head with a .030 cometic gasket and a tick sns stage 2 cam, 227/235 .618/.605 LSA 110+3
I bought the .030 gasket to bump my compression but keep reading about compression/quench/spuish and now am wondering if buying the .030 gasket was the right move.

 

Use this:

http://www.wallaceracing.com/cr_test2.php

The pistons stick up above the deck on stock bottom end LS engines. The last one I checked was .006" out. With a .030" thick gasket, you're probably going to have problems.

 

You'll want a minimum of .033-.034 quench. Most most Ls have the pistons sticking out around.005 or so. Your pistons could end up hitting the heads. Ls are a lot different than sbc where the pistons were usually way down in the hole

 

I went with the trick flow 220 as cast heads 61cc chamber cam is 232/236 .600/.600 114 +4 LSA and a .040 cometic head gasket.... should I of stayed stock .051 gasket???

 

whats the difference between milling the head vs running a thinner head gasket as far as ptv goes? either way your bringing the piston closer to the valve

 

Milling the head doesnt bring the cyl head deck any closer to the block deck and piston while using a thinner gasket does. Both change ptv but thinner gasket does both ptv and quench, piston to head clearance.

Valve angle will also change how much your ptv changes based off how much you mill.

 

okay thanks. this is my first build so I expected some errors. already torqued down both heads with new factory tty bolts, ordered wrong length pushrods, exchanged for correct length, and now may have to get a thicker head gasket...then will need those longer pushrods I originally ordered sent back to me lol

gonna have to measure ptv

 

I know it sucks but it's better to pull those .030" gaskets off now in favor of some .040" gaskets rather than later when you are forced to because your quench distance was too tight thus creating problems which would end up costing you alot more aggravation, money and time to fix. We all makes mistakes, fortunately you posted up about it before running the motor so it's all good.

 

Hi 99T/A, I would NOT remove your heads at this time.

I ASK :
Crankshaft Material and Stroke ?
Rods OEM/Forged ?
Pistons Cast/Forged (2618/4032) ?
Engine Operating Range/Max RPM ?
Pin Offset OEM/Custom ?

I can calculate your P/V using EAP
Guessed Facts = Your +3 Advance L 107 Intake C/L with MY 110 Intake C/L
L +3 (107) = E of .095" and I of .065" P/V
MY "0" (110) = E of .077" and I of .084" P/V

My RECOMMENDATION, do NOT BELIEVE the "hip shot" TECH, use Math.
My RECOMMENDATION, believe the Empirical Data, not guesses.

I have data with MY reports of piston/head contact, (my personal engines) you would be surprised, just ask ?

The difference in distance we are speaking about is the thickness of ONE of the hairs on your head ! (the quench distance)

Few here will state the amount the AL block grows (deck) when up to temp, then they state the timing chain will become "tighter" when the block is up to temp ?

I DO NOT create the "tech" reports here, just my own, with those other reports read found "funny" like the laugh is get when watching CNN.

Lance

 

I am running the .030 gaskets with no issues.. 243 heads lightly milled for clean up and I had plenty of PTV clearance. Build specs are in my signature..

 

Are you running .030” gaskets or .040”? Your signature says Cometic .040” gaskets.

 

Oh damn good catch.. I was reading the thread thinking, what is the problem?! Lol I did mean .040's.. i see the concern running .030s that would be an awfully tight PTV and quench . Total brain fart, I apologize for the confusion

 

So after measuring ptv I have found it is tight. I used some playdough to measure. made up some solid ls1 lifters, dropped in my 7.375 pushrods and rotated the motor twice, removed the head and looked at the playdough.
i didnt measure but on the intake side the valve just barely cut through so that you could see the silver of the piston. but the motor turned freely, never felt the valve make contact. The exhaust came nowhere close.
So now my question is if I have basically 0 clearance, going to a .040 gasket would only give me .010 of slearance correct?

 

Could retard your cam a degree and try it to for additional clearance

 

You need to use an adjustable pushrod set to zero lash to do it right. Using the 7.375" pushrod probably opened the valve when the rocker was tightened, making your PTV measurement tighter than it really is.