I recently bought a '72 Supreme with a 350 4bbl motor. Car runs great on the road feels a little sluggish off idle. My question is should this car have an idle stop solenoid to help with maintaining idle speed under load. My car doesn't have one, there is a bracket for one however. It seems to run better off idle without the A/C being on. Thanks for any help.

 

I think the idle solenoid was actually an anti-diesle device . Wired to the acc post on the starter , it held the idle open for idle speed , and when key was turned off it de-energized and let the the throttle fall below run-on speed . So no knockity-knock for 2 minutes after you shut it off .

How ever I'm with you on this and am using mine to bump-up the idle by wiring it to the A/C clutch relay .

 

Don't confuse a solenoid with a slow idle dashpot. The latter has no wire or electronics -- only a spring and internal damper to keep it from moving too fast. It was used to keep the throttle from slamming closed too quickly which can upset the mixture enough to stall the engine.

The usage of the dashpot changed over the years. Some applications that often used a dashpot were those with A/C and/or those with manual transmission. Automatic cars without A/C might not need the dash pot, since the engine is back-driven through the torque converter when you take your foot off the gas.

Sorry I don't have a specific answer for your '72 Supreme. But if there's a bracket and it looks original, then you can bet there used to be a dashpot or solenoid, depending on which was used in '72.

 

Actually, according the the chassis service manual, the idle solenoid is used as part of the low idle setting procedure if the car came equipped with the solenoid. reference: page 6M-37

In it's capacity as a solenoid, the idle is set while the car is running and the solenoid is energized. Once the key is turned to 'off', the power to the solenoid stops and it retracts - and prevents dieseling too.

 

Thanks for the responses guys. Any thoughts on improving slow speed drivability with the a/c on? Runs great w/out a/c but that's not an option during a Mississippi summer.

 

I installed an electric idle stop (pick and pull) on mine inline with the compressor. brings the idle back up with the AC on. Works great.