If #3 is 170 psi after a few proper, consecutive valve adjustments, that cylinder has an internal defect. Usually, if it has been a long time since a valve adjustment was last done we suggest doing the job and then doing it again after ~500 miles or so. The idea is that after so long, Carbon builds up around the tight valve's loose margins and the first adjustment causes it to be broken away. That leaves the valve margin loose again, so the second adjust sets it for real.
Something's broke. We can't know what unless you do some digging.
11-21-2015, 03:11 AM
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