Low compression

[Tony Wheeler]

Originally Posted by Lynn Eades

Another coincidence is that the compressions on the low cylinders are the same on each bank 30,30, and on the other bank 50 and 50. Very unusual.

Another very astute observation on your part Lynn, which escaped me completely! Strangely it seems to point even more strongly to head gaskets as mentioned: "perhaps BOTH head gaskets are leaking between adjacent pots..."

I don't know the likelihood of that, as it's quite some distance and would normally involve water jackets, but it would certainly explain equal compression in adjacent pots, because they're both leaking through the same passage (in the opposite direction).

Of course, even it were possible, there would need to be some explanation for it occurring on BOTH sides. I wonder if it could occur in a rebuilt motor if the heads weren't torqued (or re-torqued) properly. Might be worth warming it up and re-torquing heads before next compression test, taking special note of the central stud (which is first in the tightening sequence anyway).

Again, it's a longshot (extreme longshot...?) but very easy to do and always worthwhile anyway.

[Keith Webb]

Just came across this Ford film featuring valves. Won't necessarily fix your problems but may at least be a distraction! https://www.youtube.com/watch?v=-x9HIZuTmsE