nj67

My cars normal idle after startup and choke off is 800rpm, occasionally not always after a long ride idle in neutral will be about 1200rpm. I say after a long ride because I can not recall it happening on anything under an hour of driving. Well I plan to take a look at carb tomorrow but pretty sure I will not be able to duplicate the problem in driveway. Anyone know what might be causing this?
Thanks Chris

oddball

FWIW, I had the same symptoms - high idle after driving - that turned out to be the secondary throttle plate rod. The rod was slightly warped. It opened and closed just fine with the engine off, but with the engine running would stick open just slightly.
So something to check. When it'd idling high, open the hood and make sure the primaries and secondaries are all the way closed.

pappyl

Also on checking the obvious stuff,
The idle selenoid may be sticking (possible not working until it gets hots). Once off cold choke see if the carb idle stop is resting on the idle scre - shouldn't be - should be a gap there - as the selenoid is holding it up - this is to stop run on after shut-off.

442mark

I had a similar problem, but it occurred even after a few minutes of driving. Turned out the light-weight aftermarket distributor mechanical advance springs I was tuning with would not let the advance weights return all the way in unless I would drop the rpm down a few hundred or so by slightly releasing the clutch with my right foot on the brake while stopped (stick shift car with no choke, no vacuum advance & a large cam that liked to idle ~1100 but would be ~ 1400 after a short cruise). Shutting off the engine and restarting it solved it as well. It baffled me for a long time and thought maybe there was some binding or rubbing in the area of the distributor between the weights and the rotor. From the beginning I had greased the pins & plate that the advance weights slide on & their movement was smooth without any sticking, bottom side of rotor had plenty of clearance too. Went to slightly stronger springs and the problem went away, go figure...