I am putting together a stock cube LS1. I have a set of new GM MLS gaskets that came with the shortblock, but I have room to run a .040 cometic. The cometic would bump me up to 11:1 from 10.6:1 with the GM gasket. Is it worth the extra $100? I am using stock LS6 243's, and a F13 112.

 

If you have the clearance, opt for the 11:1.

 

compression is the key to a good combo, period.

 

Do you have to deck the block to use a .040 cometic to ensure that they seal correctly?

 

I have a MS3 114 LSA w/ 243s and I couldn't use .040 cometics without flycutting

 

no, they come with instructions, follow them and your fine. block prep is very important, they are coated with a sealer as well, iirc

 

Do you have forged pistons with valve reliefs?

 

Well i only asked because I know alot of people that had these and they leaked, also the guy putting my motor together said it would be very smart to deck the block to run these gaskets and he recomended that I ran a stock GM gaskets if I did not want to pay to deck the block.... needless to say, I just milled the heads down more to make up for it.

 

I still can't believe he traded you.

 

my buddy is running .040 cometics on his stock shortblock with tfs 215s (out of the box) and has had no problems. he is also shifting at 7k and bouncing the 7200 limiter quite a bit with his built t56 and 456 geared moser 9".

 

It worked out well for both of us, IMO.

 

Engine builders often consider compression to be "free horsepower". Because adding a little bit always adds some power and torque, but since you are already running premium not using all the compression available to you is like wasting gas.

So, up the compression and save the Earth? maybe, but it'll be more fun for sure.

Josh

 

Stock GM MLS headgaskets, stock pistons and no valve reliefs