18RG compression test results.

[maurice c]

HI guys,
I have searched for this one but found no definite answers. I was looking at an RG in Sdyney a couple of days back that gave me 120 125 125 120 on a compression test, I was expecting about 145 a cylinder. How tired is this motor? Its a 250 head. Thanks.

[Major Clod]

My freshly rebuilt (ie not even run in yet) 88253 head RG with standard RGU pistons (8.7:1) pulled 160psi per cylinder at operating temp the other night, if that gives you any help.

[Steve M]

9.7:1 0.5mm OS pistons with 88253 and 88270 head using 88251 cams got 180-188psi.
same pistons using 88270 head and 30/70-70/30 reground cams got 190-198psi.

[Steve M]

The limit is around 142psi anything below that needs rebuild straight away.
179 is stock for 9.7:1 pistons.

[maurice c]

thanks fellows

[The Witzl]

yep i get about 180psi for my rebuilt 9.7:1 pistons with 88253 head.

[allencr]

Wet results?

[maurice c]

thats dry only.

[tricky]

Cold? Expect results to be low for cold tests. 5psi between cylinders isn't bad.