windsurfnut

What should the cylinder compression be on a 5.7L 350 EFI motor (1999)

windsurfnut

dumb question, but I've only done compression checks on 2 stroke motors with kill swtiches, but what is the best way to disconnect the coil to avoid sparking/coil burn out when doing this test?
Please be specific, I'm in learn mode here!

jayhawk261

As long as your kill switch is in the off position, you should be fine. I just ran a compression check a couple of weeks ago with no problem.

windsurfnut

I don't have a kill switch.
Anyone on the proper compression numbers on this motor?

1BIGJIM

iTrader: (1)

Just take the coil wire off. The PSI should be around 140-150.
As rule of thumb all cylinders should be with 10% of each other.
You don't want to see 150 in one and 90 in another

windsurfnut

By coil wire, I want to clarify. Is this the wire that goes from the coil to the distributer?

Dave_N

On an engine equipped with the Delco EST distributor I usually remove the two harness connectors at the distributor, for T-bolt systems, I just take the wires (purple) wires off the positive side of the coil. Just removing the coil wire is not a good idea.

For a good compression test you should have a fully charged battery and the throttle plate wide open. It's ok to do it on a cold engine. You probably should see about 170-180PSI on an EFI small block. Big block would be more in the 145-165PSI range.

Dave