I've got an LQ4 shortblock that I'm putting in my car here in the next couple months, and I was just wondering a few things. What kind of power increase would I see by switching out the dished LQ4 pistons for the flat top LQ9/LS2 pistons, to bump the compression up? The setup will be most likely, fresh 6.0 iron block with stock internals and ARP hardware (LQ4 or LQ9 pistons), Torquer V.3 cam, and stock 243 or 799 heads. I've also been thinking about just maybe porting my stock '98 heads, but I hear they're the worst LS1 heads. The only way I'd port them, is if I could get them to outflow stock 243's or 799's for a comparable price. Any help would be appreciated. I'm just trying to see if the power increase, by the bump in compression, would be worth spending the money on some LQ9/LS2 pistons.

 

When I had 241 heads, ~10.0:1 comp, I was at 391 rwhp with MS4. With 799s, the comp was ~10.5:1 and power jumped to 417 rwhp with a slipping clutch. Tuners thought maybe a few more ponies if it would of held. SO that was ~25 rwhp with a 0.5 bump in compression AND flow. Try and use your knowledge of engines to guesstimate what your setup would be, or wait for other replies. I would guess along those number lines though.

 

Now, after some research, I'm thinking of actually getting some L92 heads, and LS3 intake. It seems like the flow of L92's is going to be hard to beat for the price. Any ideas on compression with the L92's with either LQ4 or LQ9 pistons, and what kind of power, and if I'll have PTV issues with the Torquer V3, and that setup?

 

If I recall correctly, a full point of compression change is worth about 4% in power.