Originally Posted by cjskotni
All,

I have bee tinkering with my Charger trying to get some of the long-lived bugs out of it. One thing that has evaded me is getting rid of the horrible off-idle stumble. If I give the car more than half throttle from a stand still, it stumbles....much more and it will jump forward and cut off. Once I am moving I can blip the throttle and she is nice and crisp. This is just an off-idle issue. I swapped out the white cam and (28?) accel nozzle to the red cam and 35 without fixing it. Here are the specs:

- 73 Charger - 500ci engine 10.6:1 compression, mild.483 lift cam, 2500 converter, 727, 3.55 gear, 20* initial timing
- high rise single plane intake + 1/2" spacer
- Holley 4150, 850 cfm vac secondary (single pumper), red cam, 30cc, 35 nozzle

If this is so bad that it cuts off, I feel like I must be a mile away from what it wants. Otherwise runs pretty well. Very crisp at speed and pulls hard - just this annoying bog when you are getting moving.

Any suggestions on what to try next? I just swapped in a 45 nozzle (hollow screw) but it started raining so no testing today. I am hoping somebody here has a similar combo and could give me an idea of where to start.

Thanks in advance! thumbs


First things first. Ditch the red pump cam and use a blue one. Adjust the pump so you use ALL the pump stoke. I never leave .015 at the end of the stroke.

You have a pretty tight converter. It make take a big, short pump shot. That’s what the nozzle controls. The bigger the nozzle (.037 verses .028) the more volume you get and it it’s shorter in duration. The opposite is the smaller nozzle gets less fuel for a longer duration.

You didn’t mention power valve opening, but it’s important. You need to hook a vacuum gauge to manifold vacuum (not ported vacuum like is used for a vacuum advance distributor) and drive the car while monitoring the gauge. See what your vacuum is at a CRUISE and then set your power valve opening by that. I suspect you’ll have 16 or more inches at a cruise. That’s means unless you can find something that opens higher than 10.5 inches, you need a 10.5 power valve.

Do not set your power valve opening by idle vacuum. That’s wrong. Set it by cruise vacuum.

Start with that. As for the accelerator pump...the goal is to use the smallest nozzle that keeps the stumble out of it. If you need say an .045 the that’s what it needs. But, if you can get everything else in shape and you can use say a .033 nozzle without a stumble, that’s what you use. It will be better on fuel mileage and it will drive better.

Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston