I am building a 370, ie a LQ9 that is .030 over. I have noticed that most of the pistions that are 4.030 are built for 6.125 rods. I am reusing my LQ9, 6.098 rods and have 64cc heads. I was going to use flat top aftermarket pistons with valve reliefs. Does anyone know how much compression I will lose by running the 6.098 rods versus the aftermarket 6.125 rods, since the compression height will not be as high with the shorter stock rods? Thanks

 

compression height isn't an issue, the pistons setup either way at hypothetically 0 deck.

I can assume your using Mahle pistons?

0 deck with 6.0 MLS gaskets i'm showing 10.87:1

 

I haven't bought any yet. I was just looking around at them doing a little research to see what my options are. Since the motor is going in a truck and is naturally aspirated, I am trying to not give up any SCR.

 

Are you saying you want to use a 6.098 rod with a piston designed for a 6.125 rod?

 

The pistons are speced for both.

 

If the only difference is compression height, you won't see a change in compression ratio assuming you use the correct rod for the correct piston. Your rod/stroke ratio changes with the rod change, but not compression.