When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My project car 350 cu.in. needed to idle at 750 to keep it from stalling when shifted into reverse or Drive....which sometimes caused a jolt to the drivetrain (auto trans).
I did a complete tuneup/also readjusted valves/reset timing/adjusted floats in Holley carb….
now 550 rpm idle is perfect...no jolt/no attempts to stall when going into gear.
Is it the original carb? What gas are you running?
Here's where I'm NOT an expert, but I remember reading in a Pontiac Magazine tech section years ago how they'd idle great at 550 perfectly back in the day, but difficult to get on modern pump gas. However with minor mods it's possible. OK that's all I remember, I don't recall the details or mods outlined. People ...come and tell me i'm full of it ...or if there is merit to what I recall (go easy, the gears don't turn as fast as they used to) ha ha.
If you need to have it idle at higher than what the emissions sticker specifies (and your engine is stock), you have a vacuum leak [somewhere], timing issues and/or carb tuning problems. There are MANY reasons for having such problems, but almost all fall into one of those three categories.