Really High idle after warm up on 360

360/ Holley street dominator vac secondaries/auto/MP
Distributor.

Car starts no problem, run fine except once it warmed up the idle will stay high like 2k rpm. Sometimes it slowly comes down to 1100rmp but normally it’s 850ish. Throttle is on the idle screw slack in the throttle cable and kickdown cable.

Any thoughts on what the cause is?

throttle is on the idle screw & it can be 850 or 2K RPM? Just a WAG but any possibility that the dist weights are sticking (& advancing the timing)?

Thanks RapidRobert, that’s definitely a possibility. I was thinking it was possibly something with the timing. I’ll pull the distributor cap after I warm up the car and see if there’s anything sticking or binding.

Thanks

You didn't inadvertently put the vacuum advance hose on the manifold vacuum port?

The vac advanced port is plugged/not used.

Thanks

And will add it could also be due to the advance springs being to light. Get a timing light on it and see what the timing is doing.

Also, is this a new problem with no other changes ??

I would check the secondary's are closed all the way.