Compression #'s for 69' 340

[buickboy]

Low was 145. high was 180. Opinions?
thanks,
Mitch

 

[txstang84]

pretty big difference (about 20%)--is it only one or two like that, or are they all over the map?

 

[buickboy]

Just two. rest are within 10 percent
Mitch

 

[Leadfoot]

It's old. I'd say valves but that's just a guess. Do you have the throttle plates open while cranking?

 

[txstang84]

Probably right...does it burn much oil or are those two plugs different from the rest?

 

[metallidart]

I had an Olds 455 like that, just one cylinder was 205, the others were 160-165, had a wipedout exhaust lobe.

 

[RustyRatRod]

That lowest is a little low indicating wear. The highest is too high, which could indicate some cam wear as indicated. There's a spec on it somewhere. Probably around 160 PSI would be my guess.

 

[dirty white boy]

do a leak down test on them cylinders,..if thay show alright you know the rings an valves are doing there job and that you need a new cam,...if not you need to tare it down an brake your wallet out...