The Stovebolt Site Forums The Shop Area The Electrical Bay 58 283 HEI Conversion

I am getting close to the point of rewiring this truck and I want to swap over to HEI at the same time. Consensus from searching appears to be that it is a "pretty simple" swap.

Anyone have tips on gotchas to look for? My intention is to grab a full distributor from an 80s SBC (with delco electronics in it), swap a bronze cam gear from Summit onto it, and wire it up like it was installed on the later model trucks.

I know the early V8 distributor housings had a flat for the oil passage that had to be lined up properly for the lifters to get lubricated properly, but a later distributor should have a groove all the way around to remove that requirement.

The later model (mid 70s-mid 80s) SBC distributors were pretty much all interchangable, but do they match the length/diameter/etc of the early V8s?

Anything else I should watch for in this project?

You're going to encounter an extremely close fit between the big distributor housing and the firewall. Be sure the motor mounts are in "as new" condition or you'll break distributor caps frequently from torque reaction. The housing length and the interface with the oil pump drive is identical to the point type distributor- - - -no problems there. A late 1980's electronic advance HEI distributor will not work- - - -be sure to get one with a vacuum advance on it. Rebuild the flyweights and bushings in the centrifugal advance and make sure there's no lost motion- - - -they're notorious for wearing out the pivot pins for the weights. The old style distributor for the point type system with the window in the cap for adjusting the points can be converted to work with the HEI pickup coil and reluctor components, but the module needs to be mounted remotely on a heat sink. I have a system like that in the process of being converted, as well as an original stovebolt six distributor that's getting the same kind of modifications. It takes some machining to the breaker plate for a pivoted vacuum advance for the pickup, and a pointed steel plate mounted onto the rotating cam to trigger the pickup coil. The end result will be a stock-appearing distributor with hidden electronic components.

If you're running a cast iron camshaft, the bronze gear isn't necessary. The original gear will work OK unless you're also running a roller cam with a steel core.
Jerry

Jerry is right. The fit at the firewall is tight. I cut a flat tip screwdriver down just for install.
All that other info is an experienced genius at work.

Before spending any money, look at the R2R distributors. They use a much smaller cap than the HEI's ,allowing for more firewall clearance. They still use a remote mount coil . I bought the Jegs house brand for my BBC, which I believe is the same as a SBC. It's worth taking a look , imo.

Also, I've got a new bronze gear that I didn't use. My cam required a mellonized distributor gear.

RB

Per the Vehicle Information Kit, I should have a cast iron cam so it is good to know that a standard gear is fine.

The R2R distributors run a much lower voltage spark (~30k vs ~65k), but I am not building a race rig here. That should be fine for this engine.

Thanks for the tips, I will do some more reading. I am inclined toward the R2R setup with an external coil though.

Since a clean, properly gapped spark plug fires at <10 KV, all that high voltage isn't going to be needed anyway. HEI was invented to meet the government requirements in the Clean Air Act of 1968 that all emission related components, including ignition systems had to run 50K miles without being serviced. A HEI will fire a spark plug with the ground electrode completely cut off- - - - I've proved that on dyno runs for my high school students when I was teaching oscilloscope pattern interpretation.
Jerry

I have seen some pretty horrible firewall hack jobs to make a HEI distributor fit in a TF truck. While I appreciate the performance
HEI's provide, It wouldn't be my choice for a TF with the engine in the stock location.
Fred

The primary reason I want to do the conversion is to increase the service life of the ignition system, so that seems like a solid vote in its favor.

Looking at:
Distributor

Coil

Why pay all that money for a yellow paint job on a coil that can be bought at any local parts store? Try a Ford or MOPAR coil for a vehicle from the mid-1980's. It will work just as well at half the price of the Accell unit.
Jerry

The mid 80s chevy ones are the wrong resistance (0.7ohm). The 90s square remote coils from the 4.6 are also 0.7ohm.

Per the manual, this needs a 1.4ohm coil.

I will look at the Ford ones, thanks.

Ok, it looks like Ford also used the lower resistance coils (0.7ohm) up through at least 96.

The 79-91 Dodge trucks had a 1.2-1.9ohm spec, so a coil from one of those should work.

Thanks for the tip.

The only drawback to the low primary resistance coils is the current surge just as the power transistor turns on. It's almost a dead short condition until the inductive reactance kicks in. GM HEI modules have a built in current limiter to prevent module damage during that surge, but the aftermarket modules that supposedly interchange with GM eliminate that feature due to cost of manufacturing. I have no idea what the circuitry of the small cap aftermarket distributor looks like, so using the higher resistance coil is probably good insurance.
Jerry

Don`t skimp on the module. Get a high quality one.

If you haven’t bought yet, ask about the 1 or two year extended warranty. I bought the JEGS house brand,but bought the 2 yr warranty, just in case. It was 35 bucks, I think. Normally I never buy extended warranty but since the house brand I bought was about 1/2 the price of a high end MSD unit. Just a thought…..