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Old 01-07-2018, 08:36 PM   #10
Junior Member
Join Date: Nov 2014
Posts: 15
Default Re: Interpreting Compression Test Results

I started up the ol' model A today to let it warm up before re-doing the compression and doing the leakdown test. It didn't leak a drop of oil out the rear main.. Yesterday it leaked a drop every couple seconds until it warmed up. I got it up to 195 degrees and then did the compression test followed by adding oil to the bore. I then did the leak down test. Here are the results:

Cylinder. 1. 2. 3. 4.
Compression. 90. 86. 87. 86.
Added oil. 96. 90. 92. 92.
Leak down %. 58%. 20%. 70%. 20%

On the 3 cylinders below 60% the sound was coming out the oil fill pipe, and on the 2 with 20% i could hear air coming out the plug hole next to that cylinder. I verified each of the cylinders were on TDC..

Based on this I am thinking valve related issues.. Bad seats, bad guides, burnt valves, etc. Thoughts?
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