I've not fooled much with carbs or tuning them honestly, i have a 390HiPo with a .533 Crane Cam, stock heads, electronic ignition, edelbrock performer, 600cfm edelbrock. I had a 670 Truck Avenger which ran alot better but sold it for more than my cost and I am gonna get a new one later. Right now it's only hand timed by ear. I was wondering what you guys would recommend. Carb hasn't been tuned yet, Runs fine for a little while then it will begin to sputter and drop to 450-500rpm after running a little while, however usual idle is 850-900rpm on it right now. It will keep just enough to not stall out but barely sputter and run until I gas it. all is brand new and fuel system is brand new fromthe tank to the pump.

 

Oh yea it also diesels when shut off for maybe 1-3 seconds

 

To rich. .

 

Bring the engine to normal temp and set the idle, then set the timing. Now set the idle mixture by turning the idle mixture screw one at a time until you get the highest idle. Start by turning them in until the engine starts to slow down and then start turning them out until you get the highest idle you can. and then reset the idle to what ever you want. Another way to set idle mixture is with a vacume gauge. same as above but you are looking for the highest vacume.

 

set timing, carbon on pistons and chambers is a possible cause for dieseling-could run Napa's MV4 intake plenum cleaner through, works great! just change your oil after doing so.