>The symptoms are that
>it runs fine for a while, then starts choking down and dies. If you let it
>sit for about 20 minutes, it starts right up and runs fine. My assumption
is
>that it is vapor locking.
>
>Recently, I remembered that the vacuum lines to the distributor are not
>connected and never have been since I got it. Could this be my problem?
>
Hi Rob and the Eminent Listers,
I'm not familiar with this particular engine but you've done most of the
standard fixes and more, this is getting into the long-shot area but I have
an idea that might just be the problem and its led me a song and dance
before just as you describe.
The vacuum lines go to the inlet manifold (header) and you will be weakening
the mixture with them open, often the vacuum advance/retard line to the
distributor is a drilling just up-stream of the throttle disc so it has no
effect at idle but soon as you put any load on the motor by opening the
throttle it effectively becomes connected to the manifold, being now on the
down-stream side, and looks like a big air leak.
Its quite possible the plugs are being seriously cooked by this very weak
mixture which will burn very hot and they will start to miss-fire and even
pre-ignite the mixture on the way in as they're possibly glowing.
Two things you can do, plug the vacuum pipes to stop the manifold air leaks
and try again - the vacuum advance only puts a bit of extra spark advance on
the timing for high speed, part throttle cruising.
You can run it as is and the minute it starts to play up kill the motor
instantly and coast to a stop; with some gloves whip a couple of plugs out,
they will likely be deathly white and show all the classic signs of serious
overheating.
If this is the case you need to fix it ASAP as the pistons, and exhaust
valves especially, are having a really tough time of it. There is a real
possibility of badly burning one or more exhaust valves with extended
running, and if you're really unlucky a molten alloy piston crown has been
known to leave its post and go AWOL down the exhaust pipe. . . . . . . .
Should this be the case a new set of the correct grade plugs would be good
for the engine, the over-cooked ones are fit for the trash only.
Richard
(Southampton UK)
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