View Single Post
Old 01-09-2012, 05:39 PM   #2
storm9c1
*** That's interesting ***
 
storm9c1's Avatar
 
Join Date: Oct 2008
Location: Pittsburgh, PA
Posts: 2,772
Re: 120 good compression?

Quote:
Originally Posted by Asahi123 View Post
I have 71 Chevy 350/350. I did a compression test I got 120 on all the clynder. So is that good or bad? Mileage is 147,000.
Posted via Mobile Device
It depends. Shooting from the hip, I'd say it's low but reasonable for those miles. However, did you have the throttle plates propped open when you did this? If not, it may read low or uneven depending on your technique. And what is the goal here? To diagnose a problem (ie: cylinder not firing, excessive blow-by, leakdown) or what? Usually it is more important to note that the compression doesn't vary more than 10% amongst cylinders, and in that case the details don't matter as much. But if you are trying to figure out something more complicated, then the details of how you did the test do matter.
__________________
Tom
Chevy by day...
1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E
2011 Chevy Caprice PPV 9C3 6.0L
1995 Chevy Caprice 9C1
1994 Chevy Caprice 9C1 #3
1995 Chevy Caprice Wagon #2
1995 Chevy Impala SS
Mopar by night...
1969 Dodge Charger
1972 Chrysler Newport 2dr Hardtop (27K miles)

Plus others...
storm9c1 is offline   Reply With Quote