My stock points distributor to computer controlled HEI conversion

I finished converting my stock 430 points distributor to a magnetic pick-up to that signal can be connected to a GM computer controlled HEI module.
I'm going to use this with a megasquirt and a converted SPX manifold for EFI.

I used a late model magnetic pick-up that I got from the autoparts store. It's used in a GM HEI distributor. I then got a reluctor wheel attached to the shaft from an old GM HEI chevy distributor. I took the points cam and shaft off of the plate that the points rotor mounts to. I then attached and welded the HEI reluctor and shaft to the points rotor plate. I re-assembled the distributor and locked down the mechnical and vacuum advance mechanisims.

I'm going to use an 8-pin HEI module from an early 90's chevy distributor and remote mount coil. I haven't installed and tested it yet, but I'll report back when it's in.

Here are some pics:

 

one more:

 

That's pretty COOL!

Dean

 

I had IgnitionMan (Dave Ray), do one for me for my Nailhead, one of his "convertibles", to my stock point distributor. It uses an 8 pin module I mounted under the dashboard. He built the distributor with both a mechanical advance curve in it, and vacuum advance, and the ability to lock the mechanical advance out. This way, with a 4 pin module, and the lockout removed/vacuum advance connected, it works as a standard carb'd HEI system. Once the vacuum advance is disabled by plugging the hose fitting on the vacuum advance, and installing the lockout for the mechanical advance, and switching to an 8 pin module, it works for any EFI or feedback carb'd system (I use a Holley Commander 950 EFI system in TPI mode). I can switch the distributor over from the 4 pin, working advances, to locked out in less than a minute.

I'm going to have him do another one of these convertibles for my International Harvester 392 CarryAll when I EFI it soon. It too will be a Commander 950 set up as a TPI.

 

Very cool! I am going to need to do something similar when I fuel inject the 401 Nailhead in my 62 Electra. I am planning to use Megasquirt. I have looked at other options, but the Megasquirt appeals to my geeky side. :laugh:

 

Have you verified the rotor phasing? I ask because you haven't mentioned making sure the rotor is pointing at a distributor cap terminal at the point where the reluctor and armature are in firing position.

 

Ture...that will have to be something I will have to play with once it's in the car and running. I tried to put it into the running 430 I have set up in that 3rd gen camaro but the rubber fuel line from the tank to the hard line had gotten hard and cracked and fuel was spewing everywhere. So I'll need to fix that, then I can get it in with a timing light.

I wanted to build in some reluctor phasing adjustment so I may have to revise it some. One thing I'm not too sure of is if the points of the reluctor should lined up when the rotor arm is at the begining, middle, or end of the cap contact. It seems like that would affect possible dwell and timing.

 

Nope, do it before you install the distributor. If it's way off, you won't get the engine running, or you'll crossfire between 5 & 7. Then the distributor comes back out anyway.

Easy. You're going to add a fore-and-aft adjustment to the hold-down screw you're using to prevent the pickup coil from rotating.

You want the rotor to be nicely aligned with the terminal on the cap within the operating range of the ignition advance. And that ain't easy. Best bet: rotor slightly after the terminal with no advance, slightly ahead the terminal at maximum advance. You may want to bias the alignment to provide better alignment when under maximum power, even if that means that the alignment is a bit worse under idle conditions.

Dwell is controlled by the module. Timing is controlled by the alignment of the teeth of the reluctor and pickup coil, then modified by the module and/or computer. Rotor phasing has NO effect on timing or dwell. You're just synchronizing the position of the rotor to the position of the distributor cap and the position of the reluctor and pickup coil.

 

That's a good answer to a question I've had about it. I knew the module controls the dwell, I just thought that if you had the rotor/cap alignment off enough from the reluctor/pickup alignment that the module would pick up the signal when the rotor is already partially past the cap contact and you wouldn't get the full contact time needed for the spark event. But now that I think of it the dwell/spark/coil-collapse event is probably a ton shorter than the time that even a portion of the rotor/cap contact time is at even high RPMs.

So are you suggesting that the distributor is flexed outside of some tolerance when it's being stressed under heavy load?

When you say slightly before and after do you mean from center-on-center of rotor contact and cap contact, or do you mean actually not having them contact eachother when they are before or after?

I believe the module has a built-in "limp-home" advance of 10 deg BTDC if the bypass line doesn't have +5V applied to it. I'm not sure if I could somehow use this for when testing on the bench. Basically are you shooting for when the teeth on the rotor/pick are exactly aligned then the rotor/cap contacts should be exactly aligned dead center? And you're only suggesting trying to have it after at 0, and before at max adv because there's no way to get it dead-nuts-on?

 

I've never done rotor phasing when the advance is controlled electronically.

It's not a matter of flex, it's a matter of rotation. When the spark is advanced, the rotor is not going to have traveled as far around as when the spark is not advanced. So at idle with no advance, you need to have the position of the rotor--in relation to the position of the distributor cap terminal--just a bit past the point where they're "perfectly" lined up. That way, as the spark advances, the rotor doesn't get too far in front of the distributor cap terminal when the spark is trying to jump the rotor/cap gap. Since the rotor conductor is about a quarter-inch wide, and the distributor cap terminal is at least an eighth inch wide, you've got about 3/8 inch of total rotation where the rotor and cap are for all intents nicely lined up.

If that 3/8 inch of rotation isn't enough to accomodate the amount of advance, I'd prefer the rotor to be nicely lined up at max power, even if that meant the rotor wasn't aligned as nicely at idle.

 

Hmm...well now I know how useful those transparent caps can be...

 

Alright, I made a plate that allows for some adjustment. I'm able to align the pick-up points and corispond that to when the rotor and cap contacts are aligned.

Here are some pictures.

 

Other than dressing the pickup coil wires--or trimming the plate--so the insulation isn't abraded--LOOKS GOOD!!!

Why'n'cha cook up a couple for me...

 

an ounce of prevention

Guys..

Just a note here.. those of you that are using some type of HEI module.. make sure you carry a spare..

I was reminded of this at 7am this morning, when I went out to start the shop's 89 Surburban that we just finished installing a 70 STG 1 455 in.. Just threw in a 76 HEI distrib, and it worked fine, right up until it wouldn't start this AM..

I was wishing for points about then..

I always carried a module in it for the 454 it had in it, with a couple screwdrivers .. it's an easy 10 minute fix if you have the parts..

But since we just finished this up, and I am driving it to shake the bugs out before it gets put into towing duty, I had not picked up a new module..

It was the original... or a GM replacement.. but it had the pink dot on it, so I am thinking it was 31 years old..

They do fail, sooner or later.. and yes, I bought two of them this AM, put one in the distrib, and one in the glove box.



JW

 

That's a good idea. I'll be using the 8-pin sealed connector version of HEI module. It's from a '91 SBC so hopefully it has a few more good years left in it.

I once helped my wife's grandfather replace the HEI distributor in his 454 suburban. It looked like the pick-up coil had rusted and came all apart. Probably due to it not being driven much.

 

Got any pics of the 8-pin module install? Is there a handy connector that makes the wiring easy?

 

The worst part would be connecting the pickup coil to the module; you'd have to scrounge a junkyard pickup coil (or sacrifice a new one, but that'd be crazy) to get that connector. The other two connectors are available as pigtails from any "real" parts store, but you'll need a helpful counterperson to look up the numbers--or--the illustrated parts catalog so you can find 'em yourself by looking at the pictures--or--clip the connectors off of a junkyard vehicle.

In all, there are three connection points on the 8-pin module, and two on the coil (assuming you use the OEM coil that matches the pickup). So there'd be five molded connector bodies to obtain for the system.

From there, its just a matter of mounting the module to a heat sink with some heat sink compound in place; and then finding a place to mount THAT near enough to the distributor to make for decent wire routing from the pickup coil and to the ignition coil

 

OK, looks like I'm off to the local wrecking-yard...

I've got one of Dave's small body hei distributors that I was using as an MSD trigger, with the MSD and coil located in front of the inner fender...see pic below (MSD box is right in front of the coil):


I'm thinking of swapping in the 8-pin module (w/ heatsink) for the MSD box and using my existing coil. So I'd be splicing the wrecking-yard pickup coil connector onto the end of my existing pickup coil wires, and using the other connectors to hook up to the other module wiring, and making my own connector(s) to hook to the coil. Sound good?

Any idea on how to tell which pickup coil wire is which, since the polarity seems to matter?

 

Yep--as long as your ignition coil is HEI-compatible. First Guess: you might as well grab an ignition coil while you're at the salvage yard.

The original HEI pickup coil wires were white and green; they connected to the original HEI module at the terminals marked "W" and "G". Not too easy to screw up.

The 8-pin module/pickup coil may use different color codes; and I don't remember how the terminals are labeled. The HEI triggers on the negative side of the pickup coil waveform; so if you reverse the polarity the timing shifts quite a bit. An oscilloscope would make this easy...otherwise you put it together and if you have to move the distributor a bunch to get the timing right--the wires are probably backwards.

 

I have the whole set up at home(ignition coil, connectors, etc) I can take and post some pictures of...including the 8-pin pick-up coil with attached connector.