1FastCoupe

I have a fully built GSR motor w CP 9:1 pistons and full ferrea head. I warmed my motor up, disconnected the distributor and cranked it about seven revolutions but not at WOT because i didnt realize I was supposed to do that. My results are 120 120 121 121.
Is this about right for my setup? Do i need to do a compression test again differently?

NRN GT4

Disconect fuel pump fuse, hold throttle wide open and repeat the test. Write down the numbers. Then do it again write the numbers down. Then post becuase 120 is really low and something is def going on that is not right.

Is the compression guage a new one?

vaporboy12

make sure its on a warm engine too!!!

vaporboy12

your compression should be some where in the 200 area if not more

1FastCoupe

it must be worng numbers because it pulls strong for 9:1 pistons. The engine was warm during test but fuel pump was not disconnected and it wasnt at WOT. 9:1 should be around 200?

b18bEKcoupe

most likely because your throttle was closed to there was vacuum in the intake manifold.

StolenTeg

Your doing the test wrong, your compression should be well in the 200, I have an LS Build motor with 9.5 and im pumping out 210 across the board

1FastCoupe

I appreciate the replys. I will re-test and then post the results again. Thanks for the input.

turtle-eg

Nothing to wrong about because I did the same thing you did. GSR 9:1 compression... ran the engine at idle after a fresh build and then did a compression test at WOT 150 all 4 cylinders... if you did it wot, it would probably come up to 150.

I haven't done a compression check after the break in period though, but I would assume the numbers would come up because the rings would have seated.