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Trying to puzzle out compression issues on an O-290-D…
Checked the compression as part of the annual condition inspection last week. #2 & 3 were 70/80, but 1 & 4 were at 63. Can hear air escaping through the intake. A&P suggested maybe some crud under the intake valves to run it some more and check again, which I did last night after about 5 hours more running. This time I’m still getting 70 on #2 but the other three were around 40 (!). Second check was a different gauge set, but I can’t see it making that much difference unless it was failing to seal against the cylinder head. Tappet clearance is good (solid lifters on the 290-D), I just adjusted all to .007 a few days before the second check, and pulling the #4 valve cover off there’s still some small clearance even when hot so I don’t think that’s the issue. Engine starts and runs fine. At the last annual the compressions were all in the 68-72 range, I think there’s about 300 hours on the jugs. A&P suggests to run it some more, what’s the collective wisdom?
Checked the compression as part of the annual condition inspection last week. #2 & 3 were 70/80, but 1 & 4 were at 63. Can hear air escaping through the intake. A&P suggested maybe some crud under the intake valves to run it some more and check again, which I did last night after about 5 hours more running. This time I’m still getting 70 on #2 but the other three were around 40 (!). Second check was a different gauge set, but I can’t see it making that much difference unless it was failing to seal against the cylinder head. Tappet clearance is good (solid lifters on the 290-D), I just adjusted all to .007 a few days before the second check, and pulling the #4 valve cover off there’s still some small clearance even when hot so I don’t think that’s the issue. Engine starts and runs fine. At the last annual the compressions were all in the 68-72 range, I think there’s about 300 hours on the jugs. A&P suggests to run it some more, what’s the collective wisdom?
