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A short history first. My A 4 is a 1965 URJ 77414. A few months ago, while idling, my engine made a strange noise. The noise was short lived but definitely mechanical. Soon after I started getting exhaust out the oil fill which I could only assume was blow by. I injected MMO into the plug holes but there was no change in the amount of blow by. I performed a compression test with these results; cylinder #1 was 122, #2 120, #3 124, and #4 was 45. I added 10W30 and repeated; #1, #2, #3, no change but #4 went up to 70. What does this indicate to you? I ran her for 150 hrs +/- between the noise and performing the compression test. Except for the blow by, she ran fine all day, day after day at 2000 rpm.
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I would say this sounds like a badly stuck or broken valve (repairable in place, if you have access) or a broken ring (probably repairable, but will most likely require an engine pull). -
Access
Thank you for the reply. The Marian Claire has very good access based on some of the horror stories I have heard. Is there anyway to determine if it is a valve or ring problem or do I need to pull the head to see. The increase in compression after adding oil makes me lean towards a broken ring. Pulling the engine would not be too hard due to the good access. DanComment
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We see very few broken rings on the Atomic 4 (a couple in 17 years), but we see quite a few broken valve springs, so the historical precedence would be strongly in favor of a broken valve spring. With so little historical data to relate to for broken rings, it's difficult to predict much about the symptoms, but I wouldn't think there would be much of a sound associated with such a failure.
DonComment
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Thanks for the info. I hope history holds true for me. Plan to pull the head in a week or two. Have ordered gaskets, manual and valve spring. Will let you know what I find.
Dan S/V Marian Claire
Edit: Turned out to be rings.http://www.moyermarine.com/forums/showthread.php?t=2410Last edited by Marian Claire; 09-11-2011, 11:40 AM.Comment
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