Any one know the compression range for good cylinder readings (during compression testing). Mind are #1 230psi, #2 235psi, #3 235psi, #4 215-220psi, #5 235psi #6 240psi. With less than 30k miles. My problem is, excessive oil leakage out the filler cap(qt per week). I'v cleaned the pcv, it was clogged with a heavy substants (looked like petroleum jelly). My guest a water oil mix from condensation or coolant leak. If you put your finger over breather hose for a few seconds and release your can hear a tremendous mount of pressure rush out. I would expect some. Now as long as i run with the breather hose disconnected i have minimal leakage at filler cap, and when engine is up to operating temp smoke(fumes) poors out beather. And when you reconnected breather hose to a clean pvc I'm back to a heavy oil leak out filler cap.

My guest is cylinder #4 is bad which has the lowest compression, But is to low? Or could there be low vaccum from intake manfold side? Boot looked find (no cracks)Engine run smooth intal, after driving for 30 (to work) there a shimmy, rockroll (like the 240)at idle in or out of gear.

Any ideals?

Thanks Tom

Those readings are very good.

The low cylider is well within 10% of the others so it is not anywhere close enough to a bad reading to suspect that it is a compression /blowby leakage situation.

Is the vacuum port and hard vac line open?

The black plastic fitting the vac hose plugs onto down on back of intake plenum could be plugged.

If the engine is sludged up inside from pooe maintenance, it couls still have a stuck second ring and have good compression readings.

Hi Abe,

I'm confused by the compression readings on that 940 engine. I've never seen readings above 200psi on B20E, B21FT, B21F or B230F engines. As I recall, the specs for these engines range from 155 to 175 psi. Does he have a bad compression gage or a half-inch of carbon on the pistons?

The highest CR any of the engines you listed is 9.6:1. The 6 cyl non -turbo in the 960 has 10.7:1 CR. This gives higher readings.

John,

This is the 6304 6cyl engine on a 960. The compression gauge was new out of the box (that doesn't mean it's good). Tested close to oper temp less time to remove cover,coils and plugs other fart-in-round factors.

Tom