On Sun, 28 Oct 2001, Andrew Moyce wrote:
> I think I remember that compression that improves with oil in the
> cylinder pinpoints valves, is this right?
No, normally it indicates compression rings that aren't sealing correctly.
Oil will improve valve sealing only if you use an awful lot and it
splashes up onto the valve seats.
> The engine had a complete rebuild 18,000 miles ago and has only run
> with synthetic oil, which I change every 3000 miles. I've never
> checked compression before, so don't know if this all happened
> yesterday. Cylinders 1 and 4 were the ones that showed significant
> pitting on the tappets (I replaced them all).
Did you break in the overhauled engine with non-synthetic oil? That is
recommended, because the friction reducers used in synthetic oil can
prevent the wear-in required to get good ring sealing. It's possible,
although by no means certain, that your rings just aren't broken in yet.
> Is there any next step other than taking the head off and redoing the
> valves? How about the cam? It's starting to look like a long winter.
> Should I bother starting it up and rechecking the timing, or does it
> need to be fixed before it runs again?
That's up to you. The compression figures you quoted aren't great, but
they aren't disastrous either. On the other hand if you have nothing else
to do this winter...
--
Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E
fold@bcpl.net
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