cyl # 1 142 cyl # 2 140
cyl # 3 145 cyl # 4 132
cyl # 5 140 cyl # 6 145

Anybody else ever do a compression test? Does this sound OK, I am wondering why #4 is lower than the rest and is 140ish the right ballpark.

They seem fine, #4 is a bit low though hard to get to?
Try a shot of engine oil in the cylinder and try again, the oil will create a better seal, if the compression does not come up it could be a valve or head gasket?

and if it does, you just have some slightly worn rings.


not too shabby though. I put a junk yard head on my Shadow in an emergency, and the car didn't run to great... in the higher RPM'*, it would scream, but you could barely keep it running at idle. I did a compression check, and wouldn't you know it - 35 psi! yes, that'* right, I didn't forget the 1 there... it was amazing the little beasite even ran!

Most importantly is that all cylinders are within 10% of each other. You can try the oil as mentioned above, and continue to monitor the situation, but in the meantime you have nothing to worry about.

Cheers,

your compression is fine, yea one of your cylenders has lower compression, but its not that bad... i wouldnt worry about it

Aren't our cars (Series I anyhow) supposed to have around 175-180 when new? I had a compression test done on Ol Blue last summer and she showed 165-170 across the board. When I get my plugs exchanged for the correct plugs I will get the tester out and check Goldmember'* compression.

So is it supposed to be around 180 ? Im at 140 does that mean my engine is worn out?
Anybody have actual compression readings from your own cars?

any car will wear out a little bit over time. i'd be happy with the readings you have, because as it'* been pointed out - they're all w/in 10% of each other, so any wear that has occured has been pretty uniform. just a broken in engine, tis all

The online GM Service Manual doesn't give a specific psi number as optimal, but it does say;

I would guess 180 psi to be quite high.

Cheers,

Here'* a silly question:

Are all of the plugs supposed to be out while testing compression??