I have a 64 dart GT with a 225 leaning tower of power. I am running a HEI conversion with excel coil (2 years now). After the engine warms up I notice a drop in idle speed which in stop and go traffic at night results in stalling. The gauge shows that I am discharging at idle, however, the system does charge at higher rpm. The battery, regulator and alternator checkout OK (autozone in car check).

I cannot figure out what is causing the rough idle when warm?

Any ideas?

thanx

Possibilities:

Carb idle mixture too rich
Choke not opening all the way
Float level too high
Carb heat flapper stuck in "heat on" mode

Less likely- coil going bad when hot.

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What carb do you have? Mine dies if I come to a stop too fast and I have tikered with everything. Finally I decided it's carburetion and something to do with the float level. Haven't had a chance to work that yet. I just bump the idle up a bit and it idles a little high. I also thought it might have to do with tranny pressure or something related to the torque converter pulling the motor down at idle but no one here thinks thats the problem. If I was a betting man I would say it's carburetion.

Good luck

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Sweet Emotion

Manifold flash, actually. You're tooling along at some throttle opening, and there's liquid fuel on the walls of the manifold. You snap the throttle shut, manifold absolute pressure goes deep into vacuum, all that liquid fuel evaporates and the cylinders get a super-rich mixture, causing a stall.

You need a dashpot. The original poster in this thread should follow 440_Magnum's checklist for a start.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanx-I have some issues to check out.

Here is some addition information:

I am running a carter 1-barrel (BBS) with NO dashpot. The choke pulls off completely when warm and the float level is correct. The exhaust heat valve operates (open and closes with pressure) however, I am not sure that it locks open when hot-I will verify this.

The condition occurs after the engine has reached operating temperature, at night (lights on), in drive at idle. The idle slowly falls, stumbles and stalls within 30 seconds up to a couple of minutes. Once this happens the time to stall becomes shorter and shorter. The engine does feel as though it is loading up (rich)-does this sound consistent with manifold flash?

I had a similar problem with the stock coil after installing the HEI. The Accel coil has an internal resistor-is there any way to check the coil short of buying a replacement? What coil(s) would you recommend to go with the HEI conversion?

Thanx again

Dave

Manifold flash causes an immediate stall upon abrupt throttle closing (you're cruising along at 60, you yank your foot off the gas and cram on the brake -- engine stalls.)

Your situation isn't like that. You report that your idle gets ragged and eventually the car stalls. Now, you mention that it occurs at night—are you saying it does NOT occur during the daytime? The only significant difference between day and night driving as far as underhood systems are concerned is lights vs. no-lights. If you've tried driving with the lights on during the day, and the problem doesn't show its ugly face, then you might need to call in a priest to do an exorcism.

Ordinarily, your symptoms of a gradually-roughening idle and eventual stall would tend to point in the direction of carburetor percolation, which would be a handy excuse for me to recommend you do the fuel line mod to reduce percolation. (it's a good idea anyhow).

But, with your symptoms only(?) showing up with the headlights on, it suggests the trouble is ignition-related. You mention using a coil with an internal resistor: No good with HEI, which doesn't want/need any resistor on the primary side. That said, your stock coil didn't have an internal resistor and you report that the car had the same trouble, which makes me wonder about your HEI module itself. Where'd you get it, where'd you mount it, and what kind is it? I assume you did delete the external ballast resistor when you went to HEI?

As far as best coils with HEI, an MSD Blaster coil works well and fits the stock bracket.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

My HEI module fits a 1977 chevelle (NAPA #TP45) and is mounted on the passenger side fender well. I scraped the paint off and used the couplant for good ground and cooling. The coil is an Accel superstock street coil. I did bypass the ballast resistor, however, the instructions I rec' d with the conversion stated that an internal resistance coil was required.

I read the info on the gas line-my problem may be vapor lock. I plan to rubberize the system as recommended. Thanx for the tip!

Not sure what "conversion" came with instructions calling for an internal-resistor coil; that's wrong. The HEI system uses no primary resistance. That's one of the reasons it's able to supply a hotter spark.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It sounds like your alternator is not keeping up with the load placed on it at night at idle. Check for volatage drop between the battery and the high side of the ballast resister at idle. If it reads 13 at the battery, and 11 at the ballast resister, you have too much current loss in old wiring. You should see 1/2 volt drop max. You will need to replace at least the connectors, but better yet, the main wiring harness. That sounds like a big job, but if you unwrap the wires, and go at it one wire at a time, you can do it all yourself. Old amp meters will cause high resistance too, and result in the same symptoms. I bypassed the am meter on my '69 Dart, and took a wire directly to the battery, and then added a volt meter.

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69 Dart Swinger, 230 ci slant, t-5 five speed, intercooled turbo, 4 wheel disk brakes, tubular upper control arms.

Thanx for all the help. I plan on replacing the coil next payday and have already adjusted my fuel filter to 45 degrees as recommended in the postings you referenced (was horizontal). I will check out the voltage drop issue this weekend and post my results next week. I really appreciate the advice-it really helps with troubleshooting when you have a place to start.