1BadAsZ

gonna do a compression test on my car one day next week while im doing header and spark plug/wire install. should it read a certain number on the guage or just be close across the board. im just doing all the troubleshooting i know to do to try n get this thing running right. i read somewhere that its more accurate if you squirt a lil oil in the cylinder is that true? also read that you need to get the engine to operating temps is that true? i sure hope not cause its a pain getting spark plugs in and out as it is.

RamAir95TA

iTrader: (2)

IIRC a stock LT1 should show compression around ~180+ and be within 10% of each cylinder. And the motor should definitely be warm.

A little bit of oil in the cylinder helps to keep the rings temporarily sealed, but is only really used to determine a bad valve if you have low compression in one cylinder.

1BadAsZ

Now how am I gonna get the plugs out with the motor warm lol. Them headers will be on fire . Not to mention by the time I get all the plugs out it will be cool again lol. I did one cylinder the other day Just trying out the tester n it was nowhere near 170

1BadAsZ

SS RRR

iTrader: (2)

Did you keep the TB blades open?

1BadAsZ

No they weren't open, do I need to hold the pedal while spinning it?

SS RRR

iTrader: (2)

If you are starting from inside the car you need to take the PCM BATT fuse out so the injectors won't actuate, hold the pedal to the floor and then turn the engine over.

1BadAsZ

well the intake is off the car now can i still do it or is that a no no

SS RRR

iTrader: (2)

That's fine. Just make sure there is no fuel getting into the cylinders when you turn the engine over.

1BadAsZ

not possible the intake and the fuel injectors are off. had to replace intake gaskets and fpr trying to track a fueling problem which the fpr was leaking so that might have been it but im gonna do a noid light test too and then spray patter check. so the fuel cant get in there but was wondering if it would be impossible to check compression with the intake off. thanks for letting me know tho

SS RRR

iTrader: (2)

Yeah forgot that little detail about injector bungs being somehow related to the intake.
It's absolutely fine to check compression w/ the intake off.