Ive got a funny idle issue with my car. Its a 670 VS holley on a 355sbc. I start the car, choke comes on. Let it warm up a lil tap the gas and the idle comes down to 800. Start driving it and eventually the idle will work its way up to 1100. I can pull over and adjust the idle back down to 800 and itll stay that way for a few min then its back up to 1100. It only does this when the car is warm after Ive driven it for a while. What causes this and how can I fix it?
Matt

 

does this only happen in cold weather? do you have a double throttle return spring hooked up? any vacuum lines that may leak?

 

Today was the first time Ive really driven the car since putting the new motor in. I ahve a single return spring. It was about 65 here today. I the car was running between 160 and 190 degrees. Im thinking I may need a stiffer return spring.

 

try a stiffer return style spring setup. also check for any vacuum leaks, make sure your throttle cable bracket is mounted and adjusted properly. also try setting you a/f mixture screws at 1 1/2 to 2 turns.

 

Try a stiffer or double return spring. Thats likely your issue. Couldn't hurt to spray off the moving linkage parts with carb cleaner too, incase anything is starting to gum up.

 

I've never ran just one return spring. That could be your issue. I bought an el cheapo dual return spring from spectre at advance auto and never had any issues. Also, I see you're running a manual trans. you may want to look into running a double pumper carb.

 

Spray a good amount of WD-40 on the throttle linkage, as well as the choke linkage. If this doesn't do the trick, disconnect the choke lever from the flapper to keep it open constantly, just to see if the RPM still jumps to 1100 while your driving around town....

 

The double spring didnt help. As a matter of fact it made the gas pedal almost impossible to push. I have just one spring connected now and its still pretty stiff. I dont think any of the linkage is getting gummed up, this carb is brand new. Im gonna try disconnecting the choke linkage and see what happens.
Matt