Chris---The best insurance for NOT having the engine run-on is
connecting the anti-run-on valve, as when the car was delivered. Short
of that, reducing the idle speed as low as possible will help, as well
as not running an air/fuel richer than necessary. I've never found the
fuel octane to have any influence on engine run-on. An accumulation of
carbon in the head can add to the run-on. Again, this is a by-product of
a rich fuel mixture. If the head is new, this should not be part of your
run-on aggravation.
As you know, high compression makes ignition timing more sensitive to
advance. It usually shows up as pinging under load. I'm surprised you
wrote that you hear this, but "not when accelerating." That's generally
when this sound shows up. That's when it can be reduced by a combination
of higher octane fuel, and/or retarding ignition timing. Other things
can be done, but involves gadgets that you shouldn't have to mess with.
Positive Crankcase Ventilation is a way to deal with combustion gasses
that need an outlet. Your "catch tank" is an old hot rodders way of
venting these gas pressures to atmosphere. Modern ways suck them back
into the combustion process by applying a controlled vacuum from the
intake manifold to the rocker cover, via a PCV valve.
Unless you just like to do such things as "pull the pan to check the
thrust washers" and many do like to do this, I'll just mention that
excess play from worn washers can be checked by simply levering the
crankshaft back and forth from outside of the engine. Two, long
screwdrivers will do. Place one between the crank pulley and the timing
cover, the other between the crank pulley and the frame cross member. A
wad of feeler gauges down here can tell you how much motion is present,
if it feels like a lot.
Dick Taylor
'73
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