Inconsistant Idle

[zmanrc]

This one I can't figure out. Brand new motor less than 50 miles.
SBC 388 Stroker with vortec heads and intake. Had a Speed Demon 650 carb and HEI set up without vacume advance. Would set the idle about 900 and idled fine. But drive it a block, push in the clutch and it idles at 1300. the rest of the time the motor is running it idles at 1300. Shut the engine down for 5 min and restart it and it idles at 900 again. Drive it a block --- back to 1300.
Changed the Speed Demon out for my Edelbrock 750 and it does the same thing.
Changed the HEI out for one set up with vacuum advance and it does the same thing.
Changed the Edelbrock back to the Speed Demon but kept the vacuum advance HEI and still the same thing.
Assuming it has to be a vacuum issue of some sort but what? Am I building to much vacuum? Is there a vacuum leak I just haven't found yet?
Ideas???

[camaro42]

My brother in-law had this problem after getting a 350 crate put in his nova. turned out to be the spring on the accelerator at the carb didn't have enough "pull" to bring the accelerator back all the way to idle. when you let off the gas pedal, can you pull it back up some with your hand? that's how we figured out what it was. hope this helps. If not, good luck with the search.

Lewis B.

[hoogiesngrinderz]

Huh...vacuum or slight chance it is heat related. Might sound like a silly question, but is the choke on a bit with either carb?

[sman]

I was thinking choke, had a similar problem with my CJ-7 when the joke was getting stuck.

[zmanrc]

I checked the return spring like 10 times lol but installed a heavier spring and problem solved

[OIF1VET]

Sound clip!

[camaro42]

Awesome! I thought that might be it when you described exactly what my brother-in-law experienced. Glad that it's working and ready for the streets. Enjoy the new setup!