I'm running a Holley HP main body on a 350 with a Performer RPM, Vortecs, Comp Cams XE274, about 10.5 compression. The problem is, it's running so rich at idle you can't stand behind the car. It burns your eyes and nose.

What can I do about this? I'm running a PCV off of the carb, I have the vacuum advance connected to the manifold vacuum port, the floats are adjusted right, but the mixture screws have almost no effect. I can set them to get a noticably higher idle, but I could still have flamethrowers from my tailpipes if I put a lighter close enough.

The Holly main body has replaceable air bleeds. How much would those help? I have 75's in there from the factory, any idea how much higher I should go? Is there something else that would work?

Any help would be greatly appreciated.

 

do the mixture screws when turned in shut the car off?

 

sounds like you need more initial timing. that cam would want 20-ish at idle, so you'd need to limit your mechanical advance. your other choice would be to lock the timing out like I did on my vortec combo. It cleaned up my rich idle extremely well. Also make sure that your power valves are not open at idle which will cause a rich condition as well. Check them/replace them and it should help as well.

 

I'll try bumping up the base timing and see if that helps.

If I were to lock out the timing, how well would it run on the street?

 

try disconnecting the vacuum advance and locking the timing out. drive it on the street it should be fine, just don't lug the motor at low rpms. or you can try just advancing it at idle in your driveway to see if that helps with the eye burning exhaust, just don't rev the motor otherwise it'll overadvance the timing.

 

althou you will need more initial timing (recurve the distributor) you should remove the carb. flip it over. Look at the throttle blade opening relitive to the idle transision slots. make sure the blade edge only exposes about .030" of the slot on both pri and sec. reinstall the carb. do not touch the idle speed screws. Give it as much intial timing as it wants 18-26deg at idle. readjust the idle mix screws once it warms up. Locking out the distributor temperailrly (36deg @ idle) to prove the concept is ok but the motor will be hard to crank over when hot. use ported vacuum. make sure the fuel bowl screws are good and tight. (fuel cross feed).

Idealy you want a timing curve like this 24deg intial 32-36total with 15deg max additional vacuum advance at high cruise vacuum. shouldn't have to get into idle air bleeds. but could try smaller 36 on the secondary side of you have a 2 corner idle system. temperairily put two pieces of (.025-.035") mig wire in the sec idle air bleeds and see how it reacts.

 

a pic