HEI Conversion Question and Holley 2280 Lingering Issue

[nblanton]

1983 W-150 318 2-V. Mostly stock with a Melling MTD-1 cam and the aforementioned HEI conversion. OE emissions equipment is installed and (mostly) working. The thermostatic ported vacuum switches to the EGR and vac advance are effectively "failed open" but my issues are cold & hot, so not thinking those are part of the problem. Rebuilt Holley 2280 made from three different Holley 2280s until I got enough parts that were good enough to feel comfortable with the carb. Rebushed the throttle shaft on the installed carb.

Starts and idles great (most of the time; more on that.)

Coil and module are mounted on the driver fender well. Recently, I pulled the factory harness and rebuilt it using Weather-Pack and Metri-Pack connectors and made an underhood fuse/relay box to tighten up the wiring as well as to fix a few things that had been going on with the truck since I purchased it, specifically extremely high voltage from the alternator. This was fixed by adding an "ignition" relay for the voltage regulator. This relay also powers the coil. It is triggered by the original "Hot in Run & Start" circuit fed from the bulkhead connector at position 2 via J10-14RD wire.

First, the persistent issue I've had with the carb. Occasionally and usually without warning or anything I can determine to be a trigger, the needle will hang open after the vehicle has been heated up and the engine will not start due to flooding. The only remedy is to take the air filter housing off, tap on the fuel bowl, and then it will be fine. This doesn't happen after an immediate restart, but it also doesn't require the engine to completely cool down either. It is seemingly random. I have also had three different carb bodies on the engine, several needle and seat sets, and a few floats. No combination seems to be immune to this. I can't believe that this level of a flaw was just acceptable in a production carb. Sometimes I go for months without an occurrence, sometimes twice in a week.

Second issue is a random stumble/misfire. I can't tell if it is completely tied up with the rewire or if it is a slowly worsening issue. The HEI conversion has been on the truck for well over two years, I just never really cleaned up the wires until a few months ago. During this rewire I also realized the distributor was bad and it was replaced as well (reluctor was banging into the pickup; clip on the advance mechanism broke and the pickup was tilted in, surprised I saw no noticeable misfiring, or at least no more than what I had considered "normal"). That said, since I've been driving the truck since the rewire, I've noticed more and more stumbles and now sort of a random but consistent with RPM misfire. After some hunting around, I noticed that the pick-up wires are supposed to be a twisted pair. This is not the case with my set up. Would this alone be enough to cause a random and worsening misfire trend? Anything else I should look at in the interim?

 

[George Jets]

You need to run the E-coil and full 12 volts that powers it, they run cool to the touch with the Mopar HEI conversions.

Not the original tower coil and ballast resistor setup.

Simple 2 spade (+) and (-).

Exact same coil used on Ford 1995 F150. Like 20 bucks at Rock Auto.

Handy lead from mopar distributor to male post on E-Coil.

The E-Coils are designed to work with the High Energy Ignition systems.

Way hotter spark. You don't want to mistakenly grab a plug wire when it is fireing.


☆☆☆☆☆

 

[nblanton]

I've already got one of Henry's coils on the truck. Guess I left that out. The current ignition setup has been on the truck for three years now. The old ballast resistor went into the shitcan about two days after I got it along with the coil and ECU ignition module which had left a nice stain of potting material down the firewall.

I did check the reluctor gap earlier today and it was >.010" on the one I checked. .010" was the smallest brass feeler gauge I have, so I snugged it up with a .006" steel one per the factory manual. Didn't make an appreciable difference.

 

[George Jets]

Need to put a new HEI Module on there, yes they fail.

Don't forget the Thermal Paste. (Best Buy)

HEI Modules on Ebay > 20 bucks new.

☆☆☆☆☆

 

[Bewy]

It is a good idea to twist the p/up wires, but not mandatory. Check for p/up air gap, should be 0.008". Make sure there is an air gap for each reluctor tip. Contact between p/up & rel tip results in no spark on that cyl.

Keep the p/up wires away from: coil - wire, tach wire, high tension leads. Too close can induce no-fire or misfire.

 

[nblanton]

I keep seeing .008" but my 1983 manual has .006". Granted, when I checked it yesterday, it was >.010" and I've set it at .006". My truck came with the 4111950 originally.

I'll be up front that I'm definitely not a Mopar guy. I grew up messing with Fords, Jeeps, and mostly imports. So, if there is some inside knowledge about the .008" I'll set it for that. The only place I see .008" in the service manual is for a "go/no-go" check. If it's wider than that, it says to set it to .006".

That is also of course with the engine off. It's a new Chinesium dizzy, so it may be fluctuating with advance. That is something I'm not really set up to test, or at least I'm not sure how I could. Any ideas would be helpful; the manual just says to "mount in a reliable stroboscope-type distributor tester" which I would if had access to one for checking the mechanical and vacuum advance curves. I'm sure I could rig something up with a drill press, but an actual old Sun 404 or 504 would set me back more than 4 or 5 distributors. If there is a "trick" I'm all ears.

I also remember from my days as a parts-counter guy at Autozone in the 1990s (store 0499 in Gastonia, NC where the old A&P was on Franklin Blvd) when Autozone still did component testing, ignition modules were, for the most part "bad/not-bad". I do remember testing a lot of Henry's modules bad (and selling Henry's special 5.5mm socket to swap them) but The General's HEI modules seemed much more reliable. We definitely sold them, as during the 1990s the common opinion was that anything "with a brain" (Gastoniaese for "part where the magic smoke was kept", i.e. anything more advanced than a motor or solenoid) was always the problem. Additionally, the module on the vehicle is an OE GM part.

I took the truck for a drive yesterday after adjusting the reluctor gap and nothing particularly improved. I feel that it is either a wiring issue or with the distributor. At this point I'm leaning more towards the dizzy, as the misfiring seems to be more associated with acceleration. Especially off-idle and low to mid RPMs. High speed and full throttle feel smoother, but even at cruise it is somewhat noticeable, but is worse when accelerating. The truck definitely ran better with the old dizzy even though the reluctor was literally grinding into the pick-up. This three-wing clip had broken in my old distributor (not my picture) which was allowing the contact. The issue is, I found this when I was redoing the wiring, so I changed both at the same time. The HEI module and conversion was done probably close to 15K miles ago in the Summer of 2019 when I pulled the heads and changed the cam.

As for testing to see if a twisted-pair wire would improve the signal, which is likely the easiest thing for me to do, could I use a twisted pair out of a Cat5e ethernet cable as a temp test cable and if it solves the issue get a nice 18ga twisted pair with shield ordered or would the 23ga Cat5e be too small? Also, the coil wire to the distributor is routed along with the rest of the cable bundle, but it always has been since I did the HEI conversion. While the spark plug leads are standard old Packard 7mm, the coil lead is a spiral wound 8mm as I had to build it to work between the Chrysler distributor and the Ford TFI coil.

Thanks for the help so far. I know this isn't a Ramcharger/1st Gen Ram board, but I've been less than pleased with the technical discussions on the sites specifically for my truck. Y'all seem to be a much more technically competent bunch and I really do appreciate the ideas.

Also, any ideas about the carb issue? I'm positive it is something that I'm doing wrong with that as it has occurred across multiple carbs with nothing in common other than the intake they are bolted to and the person doing the bolting.

 

[Bewy]

As I said.....keep the p/up wires separate from the coil neg wire & HT leads.

If you look at the MSD 6 box [ & others ], the p/up wires exit the box on their own...& at the other end of the box from where the coil wires exit. They did that for a reason.....
Similarly, on modules such as HEI & Bosch, the p/up wires are kept way from coil wires.
Twisting p/up wires will do nothing if high voltage transients are nearby [ 200-400v back EMF from the coil ]. I use microphone cable for p/up wires & earth the shield.

 

[nblanton]

Update.

Decided to check the simple stuff and thought I had figured out the issue. I made a twisted pair cable out of an old distributor pickup cable end and two female insulated connectors. Installed that and moved the coil wire away from the new jumper between the module and distributor. Drove the vehicle about two blocks and immediately felt the stumbling return. Turned around went back to the house. This time I swapped the female disconnects on the HEI module. Drove about 80 miles. Truck ran great. Thought I had figured it out. However, it had no power at idle and would die if the steering wheel was turned in a parking lot. Figured I would probably need to go back through the carb settings and ignition timing since I had fiddled with the module wiring. First thing I noticed was that I could not get the idle speed to drop below around 850RPM even with the idle screw completely out. That concerned me, so I threw a timing light on it, and it was advanced around 28 degrees. So, I figured I would need to reset everything back factory including base timing and carb idle settings.

After doing all this I had 12 degrees BTC @ 750RPM. I then reset the idle mixture using the factory propane assist method. Readjusted the accelerator pump linkage to zero clearance and the mechanical power valve to the new idle throttle stop position. Then reset the high idle speed, which took a lot of turns to get to 1500RPM, which should have set off my spidey senses, but so far everything was working well.

Jumped in the truck for a test run. No power whatsoever. The more throttle I gave it, the more sluggish it ran. I then reconnected my timing light and did some checks to see how the advance curve was. Well, it was the opposite of advance, as soon as it came off idle, the timing would retard fairly dramatically. At a steady throttle position, as engine vacuum would build I did get vacuum advance to pull a bit of timing, but the engine was steadily loosing timing as RPM increased.

At this point, I swapped the leads back just to see if the timing responded similarly. Well, it didn't, granted the base idle with the leads swapped was around 300RPM and timing was about 18 degrees ATC so, barely running. I did managed to grab the throttle linkage and get it to rev up and the advance did work in the correct direction.

I'm leaning to having a bad ignition module. The attached pic is the diagram I used when I originally did the conversion years ago. It ran fine like this for years until the original distributor ate itself and I replaced it. It was actually running pretty well even with the pickup grinding into the reluctor wheel.

 

[Bewy]

Those modules are pretty cheap. I would replace it. Use heat transfer paste between it & the mounting. NOT dielectric grease!