84_chevrolet

iTrader: (1)

I found an iron block ls1 to go in my truck it has 706 heads on it, what kind of compression ratio should it have?

dmelvin

iTrader: (8)

There's no such thing as an Iron block LS1. It sounds like you've found a 5.3. Can you verify if it's been bored out to LS1 specs by chance (3.91)?

84_chevrolet

iTrader: (1)

Yes I can verify the motor is a 5.3 bored to an ls1 an has 706 heads installed on it. The motor runs, but I wanna know if I can put it in my 05 gmc sierra and still run pump gas

dmelvin

iTrader: (8)

K... that's what I wanted to know.

The 706 heads have a 61.15cc Chamber

The 241 (stock LS1 heads) have a 66.67cc Chamber

So it'd be like running on a set of .035 milled heads roughly. (using .006 = 1cc)

Roughly, you're looking at 11.1 : 1 CR according to LS1tech:
(https://ls1tech.com/forums/advanced-...ume-vs-cr.html)

I would say as long as you're planning on running 91+ oct. with a tune that's spot on, you could get away with it, I would wait for a couple other guys to chime in just to verify though, I don't wanna be the a$$hole responsible if you ruin the motor.