Erratic idle when eg at traffic lights

[drichards]

I have rebalanced the triple cabs, am happy with fuel mixture, changed the spark plugs, inspected the air filter, always use 98 octane fuel and try to ensure it never gets more than roughly 6-8 weeks old. I have an Ignition123Tune+ distributor set up professionally. The car idle is set at around 800rpm. However sometimes it flickers up and down to 600rpm, when idling. Am I being paranoid or is this “normal” for an engine that will be 62 years old in March 24!,

[bitsobrits]

Not normal, but probably not much to worry about. What's most important is how it runs over the rev range when driving. If the plugs look happy after doing a plug cut or two, then I'd be inclined to leave it alone.

But...If you can't leave it alone, a couple of culprits that comes to mind are wear in the throttle bushings, or a just on the "edge of correct" fuel mixture. Try adjusting the mixture a bit richer from current (say about 1/8 turn) and put some miles on, then same thing going more lean. If one of the changes works, then perhaps go back 1/16 turn and see if it's settled.