I spent part of this summer's vacation in France, trying to keep up with
with a friend in a Westfield Seven. One day we stood bent over my B's engine
compartment admiring a knocking sound from what is presumably a worn valve
guide, when on an impulse my friend lifted the oil filler cap to improve the
sound quality. What happened then is unspectacular but I just can't figure it
out: we got a very noticable increase in RPM. How the heck is that possible?
I had one carburettor running too rich at the time, but apart from the one valve
the engine is performing very nicely. I don't have compression readings, but
considering the car easily reaches 90 mph I assume compression is OK.
I don't think there is an actual problem here, but I'm just dying to know why
lifting the cap increases RPM. Any comments welcome,
Frank
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