The Dodge Challenger Message Board

As some of you know from previous messages I am having some difficulty getting my 70 rtse to idle well. I have a california emmissions Holley 625 or 650 cfm carb on the car. We curved the distributor a bit and got the ping , under load, to go away. I have a Mopar Performance Purple cam installed with 474 lift and 280 duration. Heads have been done .040 over and everthing else is fairly stock. Fuel pressure is good, vaccuum is at 15. The problem now is that it seems to "diesel" or knock a bit at idle after it has been warmed up completely. I am going to put a Holley Street avenger on it with 670 cfm and bigger jets. Maybe it needs a bit more fuel at low rpms to stop the knocking. Does anyone think this cam is a bit much for a 383 with 9.5:1 compression? Dave, I know you have commented many times on my carb issues - maybe some feedback on cams is what I need.

Correction - my cam is MP # P4452993 with .474 lift and .280 duration. The o-lap really jumps up on this cam to 60. Can that be a bit too much with a stock intake and exhaust?

Forget about the cam.

OK Steve. If you really want help to fix this you need to do a few things yourself and give us the answers we ask for.

First of all. Stick a gas analyzer up the exhaust so you can read what the mixture is.

Next fit an accurate meter that will read engine rpm between the -ve of the coil and chassis. Red lead on the coil, black to chassis.

Now take off the tube from the distributor to the carb and fit a vacuum gauge to the carb 'spark' port.

Start the car and warm it up. At hot idle check the vacuum gauge. Open the throttle a little by turning the idle speed adjustment screw clockwise. Do this until you can see vacuum on the spark port. Now close the throttle slowly until the vacuum JUST disappears.

Now set the mixture so it reads right with the mixture screws.

Here is the question I need to know the answer to.

What rpm does it idle at now if at all?

Just changed the 600 cfm carb to a Holley Street Avenger 670. Car idles great at about 1,000, with no dieseling or knock on 94 octane fuel. The carb seemed to do the trick. Fuel pressure is good and vacuum is good. Still playing with the advance on the distributor since it is pinging slightly under load when full throttle. I appreciate the tech talk you given me but I'm a complete novice Dave. I was able to fit the carb and tweek the advance a bit but thats all I'm good at before I hurt myself! Now that I have the low end idle issue fixed what would you suggest may be causing the ping described above?

How many degrees total have you set it for? If you don't understand what I mean by that read the section on setting your timing. Aim for 34 degrees and see what it is like then.