If you're going to run a mild cam, theres no reason to run a huge amount of compression.

What is this going in? Is it a DD?

 

I believe what grey matter is refering to is that, with an Ls1 rotating assembly, the 243 heads raise compression from stock. The 706 heads he has from his 5.3 would then raise compression even higher if desired.

Personally I believe the 243 heads are the way to go. They give you a bump in compression (on a Ls1 rotating assembly) and have bigger valves and flow more than the 706 heads.

 

the 706 valves are smaller also
706/862-1.89" intake 1.55" exhaust
243 - 2.00" intake and 1.55" exhaust

I think anything larger than a 5.3L needs a bigger intake valve, inorder to let those big bad boys breath. If you get an LQ9 and put 243s on it you have a LS2 besides the crapy intake manifold and cam would be 11:1 compression also. If you're running premium fuel I would say no higher than 11-11.5:1 compression for a dd

There is no replacement for displacement, except for boost and nitrous haha

 

Agreed.

 

Engine Size and Compression Calculator

This will get you in the ball park of compression range you want

 

Thanks for the help, think ill just be better off with buying a ls2 or ls1

 

LQ4/9 for the win! More power per dollar.

 

^

 

I'm scared of aluminum blocks for longevity! Plus Lq4/9 can be found way cheaper and easier than most aluminum Ls1 or Ls2 blocks