insane
Expert
I was curious if there was a preferred way to lower compression through head gaskets. Triple oem or have a custom gasket made. If custom is the way to go what thickness is good for running 10 psi through a mpi stage 2 s/c at sea level on 91 octane. Also what would shimming the head and running 10:1 pistons have for an effect on being able to run higher boost on lower octane fuels?

kinger
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I think Cometic (Sp?) already has a 10:1 gasket I have it in mine.
rxrider
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Single thick head gasket or head shim is better than stock head gaskets stacked. Been there done that, blew out my 3 stacked gasket once, ride with 2 gaskets stacked as of now but will go with single gasket this winter.
HURRICANE
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it is recommended to use up to a maximum of 3 layers of material for a MLS head gasket for a good seal.Thats why we keep many different thicknesses of Cometic gaskets in stock
rxrider said:Single thick head gasket or head shim is better than stock head gaskets stacked. Been there done that, blew out my 3 stacked gasket once, ride with 2 gaskets stacked as of now but will go with single gasket this winter.
times 2 on that, I blew out my 3 stacked as well. went with 1 factory gasket, 1 .040 shim and 1 factory gasket.
insane
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Thanks 636, how many miles have you put on the new set up with the .040 shim?
I didn't get much time after that set up, maybe 50-60 miles on her. The highest boost that set up seen was 20-21lbs. on 116 octane fuel. still held no problem.
I run 12lbs. on 91-93 octane all day in NY without a problem. But I make it a very good habit not to stay in the throttle for more then a 800-1000 foot race.
I run 12lbs. on 91-93 octane all day in NY without a problem. But I make it a very good habit not to stay in the throttle for more then a 800-1000 foot race.
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I thought that I would post this for all to see
The best practice is always low compression pistons,however,that's also the most work.If you are not wanting to take the rotating essembly apart to install pistons,the next best thing for you would be a head shim from Powderlites .I also recommend a set of chrome molly head studs together with a torque setting of 45lbs.That will help to give you some extra clamping force on your gasket and also the studs will not stretch like the stock studs as the boost comes up.When you are installing your head gasket,clean the block and head with laquer thinner or equivalent and install the gasket dry.Lube the nuts with a moly lube both in the threads and also where the nut turns on the washer.This adds 10lbs clamping force over being lubed with oil.We use Cometic gaskets in our engines because we require many different clearances,depending on the requirements of the particular engine.By the way,be sure that your head and block are straight within .0015".If you follow the above practices,you won't have any head gasket issues
The best practice is always low compression pistons,however,that's also the most work.If you are not wanting to take the rotating essembly apart to install pistons,the next best thing for you would be a head shim from Powderlites .I also recommend a set of chrome molly head studs together with a torque setting of 45lbs.That will help to give you some extra clamping force on your gasket and also the studs will not stretch like the stock studs as the boost comes up.When you are installing your head gasket,clean the block and head with laquer thinner or equivalent and install the gasket dry.Lube the nuts with a moly lube both in the threads and also where the nut turns on the washer.This adds 10lbs clamping force over being lubed with oil.We use Cometic gaskets in our engines because we require many different clearances,depending on the requirements of the particular engine.By the way,be sure that your head and block are straight within .0015".If you follow the above practices,you won't have any head gasket issues
insane
Expert
Thanks guys. 

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