I'm building a gsr block with ls crank and rods. I'm looking for about 400-425 hp, on 93 pump gas. I'm pandering what bore size to go with. I was thinking 83mm at first or 84mm. What I want to know is what is the benefit of that extra mm. Alsowhat compression pistons would you guys go with? Thanks for any insight.

 

I've seen 400hp on stock GSR's that have lasted over two years and still going. No need to really sleeve, I'd do a 81.5mm bore with stock sleeves, 9.5-10.0 compresson.

 

Thanks. I wanted to sleeve though in case I wanted to run high boost. Wasn't sure if there was a great benefit with the larger bore size, or i would just go with 81.5. Since I'm running an ls crank would my compression still be 9.0-1 if I got 9.0-1 pistons? Since the stroke is 2mm bigger.

 

If the compression is different, how would I calculate that?

 

here's what earl (rip earl) has to say about it: http://www.laskeyracing.com/shop/maxbore.htm

 

stock bore.

 

Is there really any benefit from stock bore to say 83mm. Hp wise or lower or higher compression?