[brad11957]

Alright, I got a new 383 stroker and am still trying to get things just right. One thing I am having a hard time with is this strange idle. It usually has to Idle for a long time for it to start bogging down. I figure the idle mixture is too rich. So I have adjusted the mixture screws for best vacuum. Problem not solved. I pulled the plugs and they aren't wet but they do have a lot of carbon build up on them, so I am wondering if I put too cold a plug in. I am running r43ts ac delco's which are 2 ranges colder from the stock 350 had. Car runs good, and actually idles good unless I get stuck in traffic for a while. Then it's power braking just to keep it from dying. Thanks for any input.

Brad

 

[Mr Ed]

carb

what sort of induction do you run? if it is a holley type carb then it sounds like it is slowly bogging down due to slightly not enough airflow. thing to do is open up the secondary throttle blades (small screw underneath on one side) this will raise the idle so then you lower the idle using the main idle adjuster screw. In extreme cases you can drill very small holes in the throttle blades to achieve the same.

 

[brad11957]

I am running an edelbrock 600 cfm. I have been told that it is too small for a 383, that I should have at least a 750. What say you guys?

Brad

 

[Mr Ed]

600cfm

it would only be a bit small, 600cfm is perfect for a 350ci and the only problem may be that it 'goes away' after accelerating hard for a period of time(cant deliver enough fuel under high demand situations) but this can be corrected by changing jets/powervalves etc but this circuit is seperate to the idle circuit. It may still be causing your idle problem even if it is only a 600. i've had the same prob with a Holley 600cfm as i have a big cam and it 'hunted' at idle and due to the fluctuating airflow it would give it too rich an mixture and end up over rich unless i kept the revs up a bit. i opened the secondaries a touch and then lowered the main idle, it worked well but if i leave it idling for say 5-8 minutes it still starts to bog. Also if you are running an aftermarket fuel pump then you may need a regulator as too high fuel pressure will richen it up at idle too. 7psi constant pressure is okay for a 600cfm