ls3 cylinder head gasket to lower the compression ratio
 

need your help guys to find the correct cylinder gasket for my LS2 with ls3 heads for the turbo application my current compression is 10:4:0
please guide me which one to go one ??

thank

What cc are your pistons? Are they stock?

Were the heads mild at one time? Give use more details please.

I'm using LS9 gaskets on my built 370 LQ4 with 317 heads and LS6 intake. Not sure if the LS9 gasket can be used in your set-up. Regardless, you may need to go with a thick cometic head gasket if you would like to significantly lower compression. I read a little about your build... why don't you leave the compression as is and run no more than 7 lbs on pump gas? You can run higher boost when you fill up on some high octane fuel at the track. The car is going to be much more responsive out of boost if you leave the compression like you have it now. My compression is 8.7:1 and I don't run more than 7 lbs on street tires, I can safely run 14 lbs on 93 pump gas but why bother risking it? Few cars can pull on me at just 7 lbs, when I feel like showing off at the track with some sticky drags, i flip my boost controller on, add a few gallons of 110 oct. just to play it extra safe, and open her up. Really no point in running high boost on the street unless you roll race or you're racing 1000cc+ crotch rockets at red lights with slicks mounted :)

I second his sugestion. My 408 is 10.25:1, I run 12 psi on the street with pump fuel and 20 degrees of timing under boost. I also have a meth kit to help control detonation though, and I would strongly suggest a meth kit on your build. I checked into going to a thicker head gasket to lower compression and it would only drop me to 10:1. I also run VP113 at the track, I usually drop 5 gallons in it at the track while i have 3/4 of a tank left. There are other things you need to do to help but your compression is not out of the question.

How much boost do you plan on running? If you are thinking about about 5 to 7ish pounds, you are ok. You can push 7 to 9ish with a good tune. More than that a good methanol injection kit will be much better than a set of thicker head gaskets. ( Thicker head gaskets to solve compression concerns is insta FAIL ).

True, very true.

Here is my entire setup :

-6.0L 364ci LS2 with LS3 heads and intake. (totally is stock internal).

-compression ratio is 10:4:0 (i want to lower the compression ration ).

-SLP heavy duty oil pump.
-160 Thermostat.
-SLP Under drive pulley.

-Turbonitics TC78 mm .96 A/R (capable to achieve 1000HP)

-JGS 50mm Wast gate
-JGS 60mm Blow Off Valve
-AMS 500 Boost controller
-AEM Wide band air/fuel.
-inter cooler 27x12x3
-1 7/8 headers.
-MAFF less.
-Patriot gold valve springs 660" lift
- a 223/234 .600/.600 115 LSA cam .
-Nasty custom fuel system for 1000rwhp
-Siemens fuel injectors 60lb
-Dual wallbro 255lb in tank.
-stage 3 TH400 transmission with transbrake.
-8.8" ford differential.
-car weight is 2800lbs.

they are stock

According to Kentucky turbo the maximum boost i can run with stock bottom end is 12psi with out Methanol

What compression ratio are you wanting to go to and what boost level are you looking for? I did not see what head gasket and thickness you are currently running. Maybe I missed it. What gasket and currnet thickness are you right now. I don't think a gasket change is going to get you more then .5 compression change.

I think most people do not recomend more then 17ish psi with LS3 heads. A meth kit will get help you get there.

the current compression is 10:4:0 ,looking for something around 9 ,looking to run 12 psi

I have a 408 with -12cc pistons and the stock cc LS3 head with a cometic .040" head gasket. I think it comes out to around 10.25:1 depending on who you talk to. Going to the thicker .051 gasket would only get me to 10:1 from what I am told. I do not think the head gaskets get much thicker then that. I might be wrong, but still if a .011" difference only nets .25 difference in compression you would need a gasket like .150" thicker then what you already have. I don't think they make those, then you will start to run into fitment issues with intake lining up right, head bolts being long enough, not to mention you have pretty much done away with your quinch area. Have you selected a cam for this yet? With the right cam (bleading some of the dynamic compression off) and a meth kit you can run 12 psi safely. You will have to keep intake air temps under control, and keep engine coolant and oil temps low too. Adding a little VP-113 at the track will defenatly room any issues from detonation at 12 psi.

I am afraid you are in the same boat as me with the compression, in order to get the compression down to 9:1 we will have to replace the pistons. I have an expensive set of Ross pistons in it so that is not an option for me until she comes apart. But for you with stock non forged pistons and stock rods, a good set of Wiesco pistons and a nice rod might be a much smarter way to go about it.