Re: Spitfire - worn valve guides or ??
> view mirror I was getting puffs of smoke as I changed gear (on the
> overrun). I discussed this with a friend and we decided it must be
> the valve guides which were worn and oil was being sucked in and
> burned off on the overrun. So just as I'm contemplating a head
> change
Hmmm, there will be a vacuum to suck in oil on every intake stroke,
regardless of how fast you're going. The vaccuum will be higher
when the engine is revving faster, and highest when the throttle
plates are closed *and* the engine is revving. (i.e. you're not on
the gas pedal). So if you're seeing exhaust smoke during gear changes,
it's probably because the vacuum went up when you let off the gas to
shift. I'd suspect valves.
But, before I picked up the wrench set, I'd run a compression check
on the cylinders, and do the oil squirt test on any that seem low.
Put a few (I dunno, maybe 10-15 ??) cc's of oil in the cylinder and
then re-check the compression. If it goes up, the problem is rings.
If not it's valves.
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