Earlier this week I was at Frank Condelli's for some Spring Tune-Up. He measured my compression as 130, 165, 125, 175 psi for cylinders 1 to 4. This is an old engine with over 250,000 kms (about 155 K miles) with original heads and gaskets. So we were quite surprised. Our conclusion was that heavy deposits must have built up in cylinders 2 and 4. Why not 1 and 3 we don't know.

My question is: 'What is the best and safest way to reduce/remove these deposits without removing the heads?'

At present, I switched to high octane fuel and have added a large slug of Marvel Mystery Oil to the gas with a full fill. The hope is that the Marvel will dissolve away the deposit over time. The high octane is simply because the compression requires it.

Has anyone experienced this odd compression before? How did you reduce it?
Thanks in advance
Larry

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