thabao

hey everyone,

i've been planning to do a b20 swap for a while now and want to add only a I/H/E to it with using a LS IM on the b20.

through my reading, i've read that the P8R head raises the compression on a B20B from 8.8:1 to 9.2:1.

my question is, since the P8R head raises the compression on the b20B. will it raise it on the B20z that is already 9.6:1? if it does increase compression, will it then have a ratio in the 10.x:x range?

iwanttokillgod

yes

thabao

oh, so it will raise my compression? i'm sorry, but i like it when people use clear and detailed answers.

DavidNA2FI

No, that is incorrect, the P8R has a larger comustion chamber size and will LOWER your compression ratio by a lot. Do not put a P8R onto a regular B20 unless you want less than 9:1 compression. the diameter of the combustion chamber on the P8R is 83mm, and the LS is 81mm. So given that it also has larger valves that are dished, it will lower compression garunteed. I've seen info stating that the P8R has 47cc of displacement vs the LS 45cc of displacement.

joni_titi

The p8r head have a larger combustion chamber but it have to bigger vlavle who tka more place in the combustion chamber. So yes the p8r head will increase CR .It's a great upgrade whith it's better flow.