twospeed

I've heard that by using a .040 Cometic head gasket on a stock LS1 it will increase the compression. If so by how much. Is it worth the hassle? Engine is internally stock 02' Vette

Sharpe

iTrader: (7)

<--- for when/if people go into more technical aspects in a reply.

lovescamaros28

A thicker head gasket will decrease and a thinner will increase compression but I dont see it making much of a hp diff.You may increase your chance of detonation and damage to your stock engine though.

Studytime

iTrader: (15)

You shouldn't increase your chance of detonation, but rather decrease it with the tighter quench. Yes, it would be a small increase in power production, but if you weren't taking the heads off for another reason, it would not be worth it.

A thinner gasket on higher compression motors will actually be more immune to detonation than a thick head gasket with everything else held the same. Example; installing a thicker head gasket to decrease compression because of detonation can actually make the problem worse. There is a certain range you want your quench to be in. A larger quench will not help over a tight one until quench gets notable higher.

Ben T.

lovescamaros28

I think you need to research compression ratio,detonation,and pre-ignition and what causes spark knock.Higher compression ratios increase the chance of abnormal combustion(detonation)compared to lower compression ratios.I am sure you know that static compression ratio is the volume of the cylinder at bdc compared to the volume of the combustion chamber area at tdc.Detonation is an explosion that happens after the normal spark from the spark plugs occurs.Increased compression ratio results in more performance,better fuel econonmy,but also increases emissions and abnormal combustion from higher temeratures and increased mechanical energy potential.Why do you think we reduce compression ratios when running over a 250 shot of nitrous?Higher compression is asking for failure.In addition,why do you think high octane fuel(octane=a fuels ability to resist explosion or detonation)is recommended with high compression engines?Pretty self -explanatory.In conclusion,if you want to install a very thin head gasket to boost CR ratio without any ECM tuning go right ahead but dont say I did not warn you.

AintQik

iTrader: (3)

I think you miss his point. He is saying that a tighter quench will reduce the chance of detonation regardless of its increas in compression ratio. Of course if we are talking full points to full points its a differnent story, but we are talking tenths. Its kind of a trade off. You want to maximize compression to a point where you can still put timing in the car. There is a very good write up by people very much smarter than me talking about quench. Take a look for it and I think you will be surprised by your research.

brad8266

iTrader: (23)

It will increase the compression a little bit but the main advantage is the tightening of the quench area. The tight quench area will aid in fighting detonation and will help with better combustion.

lovescamaros28

Yes,I just did a little more research.I apologize he had a very good point.It does sound kinda contradictory to think that increasing CR can actually reduce detonation due to a tigher squish/quench area,but I found out I may have been the one that was slightly mis-informed.I do understand turbulence resulting in more complete combustion so it does prove a point.Here is a good link I found that kinda proved me to be wrong.http://www.chevyhiperformance.com/te...earance_guide/

brad8266

iTrader: (23)

good read man, I read that one before. Its great that you now know the truth. FWIW I run about .035 total quench on 93 pump gas with about 11.9-12.0 compression ratio with no knock with advanced over stock timing, and I live in GA where its hot. Tight quench is the way to go.

Tight quench completely gets rid of the hot spots in the chamber that lead to detonation. That is a direct result of the homogenous mixture, its a even mix all through the chamber.

Some things just seems *** backwards to common knowledge but are right. Ive been preaching tight quench for a while now.

lovescamaros28

Yeah,it was a very interesting article(added to my favorites).You can learn something new everyday.What can I say...I am fascinated with engines and performance.

brad8266

iTrader: (23)

Me too.

02RedHawk

iTrader: (17)

Funny... On another site/forum I got into a discussion with a very stubborn fella that still maintains to this day that a wise and (his) recommended measure to reduce compression (and thus in his mind reduce the chance of deto) was to swap the factory .054" gasket with .072" Cometics...and that he's done so on his 500rwhp/tq BOOSTED (10psi) Magnacharged LS2 as proof that it "works"... Yet no matter what facts were shared with him from online references, engine handbooks, reputable builders, my old engineering textbooks, etc., his refusal to believe (understand?) the role/impact/benefit of proper quench was becoming downright sad....

Still, I should have known beforehand that it was going to be a winless thread... He also still believes that he makes 415 Hp and 430 Tq at 3100rpm. (The mathematical calculation between Hp and Tq for him doesn't apply...)

Lovescamaros28 - its great to see that you kept an open mind and sought out the proper information...and was willing to admit that you learned something! (far too often people are too proud to admit such a thing!)

lovescamaros28

Thanks,eventhough I have plenty of automotive knowledge,it is always nice learning from people who have more knowledge than you on a particular subject.People who refuse to admit they are wrong will never learn anything.Studytime seems to be very knowledgeable.I could probably learn a lot from him and other people.

lovescamaros28

Yes explosion or combustion not caused by normal spark.

the_merv

iTrader: (88)

Also your Cam plays a factor with what the Compression Ratio can be.

lovescamaros28

You are right on there.Especially when calculating dynamic compression ratio.

Studytime

iTrader: (15)

"Especially?" Is there really another time camshaft timing affects compression?

lovescamaros28

Only dynamic studytime.(lol)

Spinmonster

A half point is near 7hp and 10rwtq. You would see that with a .033 gasket which is a best bet for your stock cam and 93 octane.

To answer your original question, with a .040 it should be 4-5hp and 7tq.

the_merv

iTrader: (88)

You want more power build a strong Cam, high-Compression Stroker..