Still having issues...

[jackn440]

For those of you who haven't read my last post, i have a '70 Challenger with a newly rebuilt 383. 4 bbl Carter 650, 727, mild cam, hogged out stock intake, headers, hei distributor (the kind that just runs off of the voltage regulator). At first i was having issues getting it to stay running when it reached operating temp, which i discovered was due to excessive coil heat. After replacing the coil, it no longer stalled when it reached operating temp. I have been driving the car around every day for the last week or two. For the first couple days it ran fine, and then started to get a mild stumble when lightly accelerating. It seemed like the longer i drove the car (throughout the day, long enough for it to build more heat), the worse it would get, to the point of stalling. The baseline idle is set at 1000 rpm out of gear and 800 in gear. I noticed that when this problem arises, it doesn't want to idle in gear at all, even if i hold it at 1000 with my foot. So when i come to a stop light, i have to pop it in neutral, at which point in runs fine, accept for the fact that the idle has increased to around 1200 rpm. If i put it back in gear, it goes back down to 800, and then continues to run poorly until it dies. I pulled a plug and it looks fine, not black or white, just slightly used. I don't know whether to blame this problem on vacuum or what, but if you guys have any ideas, please throw them my way. Thanks.

 

[ramenth]

What's the general spark look like? Like if you pulled number one wire and put a screwdriver in it to spark across a metal surface or if you have an inline spark check tool (available at most parts stores?)?

 

[beepahh]

leak

take the complete intake manifold off and re-gasket and seal everything you have a vaccum leak start here.......

 

[jackn440]

Spark is good, nice and blue. I'll reseal that intake tomorrow and see where that gets me. Thanks for the input fellas.

 

[jackn440]

Well i took the intake off, got new gaskets, sealed everything up, took the carb apart and cleaned it while i was at it. Just got back from a test drive, ran great for about the first 15 or 20 minutes, then it started doing the exact same thing again. It starts out as a slight miss at idle, and then gets worse until it won't run at low rpm while in gear. Has anyone ever cut the plenum out of a stock intake before? Think that may have anything to do with this?

 

[ramenth]

Still thinking on it. The fact that you say it starts out as a miss has me wanting to start there.

 

[ramenth]

Starts out as a miss in gear and wants to stall? Take a spray bottle with soapy water and spray down the plug wires. Tell me if it gets worse.

 

[jackn440]

My two thoughts this morning were torque converter, or still a loss of spark. Started it up cold and just let it idle in park for about 30 minutes, never putting it in gear. It still died, and wouldn't fire back up again for about 5 minutes. I didn't test the spark but i noticed the coil is building a lot of heat, even though it's on the fender well. What can cause a coil to build heat? I would guess poor ground?

 

[ramenth]

That's been my suspicion when said it would stumble and miss. Ignition break up along the lines there somewhere. You said earlier you were running an HEI? Is this a Chevy style HEI?

 

[jackn440]

I believe so. It's a Pertronix Ignitor system, it basically consists of an inductive module in the distributor and the only box is a Mopar electronic voltage regulator. It still has spark right up to when it stalls, but the spark seems to get weaker. Just went through and cleaned all my grounds and added a ground strap from the coil to the block. Took it for a test drive, still started stumbling and backfiring like crazy. I haven't tried the soapy water trick, i'll do that next. It's just strange that it never had this problem before i pulled the engine...

 

[ramenth]

Okay, now that you've told me that it's a Pertronix system and not a true HEI...I believe the Pertronix is going bad on you. To me it's acting like a GM HEI when the ignition module goes bad. They will heat up and break down. As you said the spark starts getting weak and the ignition starts breaking up. I take it you did the Pertronix to replace the points system?

 

[jackn440]

The Pertronix was already installed in the engine, which i took out of my 1970 Chrysler Newport a while back. I imagine the owner of that car installed it to replace the points, but i don't know how long ago. I was never really a fan of that setup simply because there was no real external ignition box. I think I can round up a different distributor and an orange box, so I'll try that next. Have you ever experienced something similar to this with an electronic ignition?

 

[ramenth]

The Pertronix was already installed in the engine, which i took out of my 1970 Chrysler Newport a while back. I imagine the owner of that car installed it to replace the points, but i don't know how long ago. I was never really a fan of that setup simply because there was no real external ignition box. I think I can round up a different distributor and an orange box, so I'll try that next. Have you ever experienced something similar to this with an electronic ignition?

The Pertronix actually started getting a bad rap for this kind of thing. The earlier ones were unreliable and would do the things you're describing. The GM and Ford ignition modules do the same thing if not treated right: i.e. treated with dieletric grease. That's what made me wonder when you said it had been upgraded to HEI. The GM ignition module under the cap will make poor contact and heat the coil. Important to use the grease on 'em. Ford mounting the module on the outside of the distributer seems to work better for heat dissipation, but as an old Ford tech, I've seen them go bad, too, leaving customers to have to do a "reboot" in traffic. (Put car in neutral, shut car off, re-crank.)
The Chrysler ECU set-up, in my opinion, is pretty danged bulletproof. The remote box mounted on the fender, firewall, etc, lends itself to staying away from engine heat, keeping the internals cool, which is important to electronics performance. The boxes do go bad, eventually, but so does everything mechanical.

 

[jackn440]

Interesting. Thanks for the info. Everything seems to point to the ignition as the source of my problem. I've been wanting to switch over to a Mopar electronic setup anyway, so i picked up a kit on ebay last night. In the meantime i'll just have to try and not drive it too often. I really appreciate your help, and i'll update you as soon as i get that new kit.

 

[Chryco Psycho]

is the Pertronics system connected to 12v at the ballast reisiter or is it connected to 8v at the coil + terminal , the Pertronics can be damaged by connecting to 8V at the coil & cause poor ignition or complete failure

 

[jackn440]

is the Pertronics system connected to 12v at the ballast reisiter or is it connected to 8v at the coil + terminal , the Pertronics can be damaged by connecting to 8V at the coil & cause poor ignition or complete failure

The ballast resistor was actually bypassed completely. I tried hooking one up when i got the car, and it ran like crap. I realized last night that i still technically had a points style distributor, so i went out and splurged on a shiny new set of points and a condenser. I've driven about 100 miles since then and not a single problem yet! Now we'll see if i can keep from frying the points with no ballast until my new ignition gets here! Thanks again for the help guys.

 

[moper]

Sounds to me like an engine that needs a good tuning hand. Why is it idling so high? Mild 383s should idle around 700rpm steady. What is the complete timing curve on this? Initial, and centrifical?

 

[jackn440]

I don't know exactly why it idled so high, maybe had something to do with the vacuum advance (i put alot lighter springs in a while back). But i got my new Mopar Performance distributor and box installed last night, and the idle seems much better. Haven't had a chance to do an overall timing on it, it was dark when i finished last night, so i just set it at 10 btdc and took her for a spin. After lunch i'll probably go finish tuning....damn, i shoulda gotten a timing tab that goes higher than 15 degrees!

 

[moper]

Invest the $5 in a Mr Gasket timing tape and install it carefully so there's no oil from your fingers on it. Wipe the balancer off with alcohol before you install it. You have to know where you are timing wise and chances are good that MP new dist will need some adjustment. Dont buy more stuff untill you have the tape in place and the timing curve properly set....lol

 

[ramenth]

Had a chance to do your fine tuning yet?