I currently have an LQ4 factory shortblock with 243 heads on it. I was offered a good deal on a factory LQ9 shortblock. What would my resulting compression be with an LQ9 and 243 heads, and would it be too high for pump gas? Thanks

 

Compression will be excellent, 11:1. And not too much for pump, I might be wrong but you have to be around twelve to one to start worrying about race gas lol.

 

What he said.. It should be right at 11to one if you use a stock headgasket. And will be fine with 91or 93 octane I have heard ppl say over 11.5 to one is where you start running into problems on pump gas but no real experience there.

 

10.2:1 is where it starts on a non computer controlled locked out timing engine with iron heads. these LS motors are a thing of beauty between the computer controlled timing the aluminum heads and chevy magic they can get up to about 11.5 sometimes 12:1 static with a big cam before you have the first issue. sounds like a cool build, good luck

 

I am running carb, but think I should be fine @ 11:1, thanks!