HEI Application Question

[Guest BJM]

I saw a 75 Buick Limited in local Pick-A-Part junkyard today with the HEI distributor. Will this fit a 430 Buick engine? If so, what do I need to make sure I remove other then the distributor?

3Jakes

[The Old Guy]

If it is a 455 engine, it will fit with no changes. If it is a 350 engine, it will require a different gear, The 430-455 has a 13 tooth gear, and the 350 has a 14 tooth gear. The only change is that you will need to run a new wire to it,as the HEI needs 12 volts, and the standard uses 8 volts. The wire in the loom for the standard ignition is a resistance wire.

[Guest BJM]

Thanks Joe.

I am a little worried about switching but my Oldsmobile friends swear by HEI and say it's such an easy swap. I suspect I can replace the wear items like the distributor cap and I will inspect. Can I / should I replace something inside like we would replace points and condensor in the old set up? Pardon my ignorance.

3Jakes

[The Old Guy]

Check the rotor and cap, and if they look good, i would put it in the engine.

[NTX5467]

Many Buick owners have upgraded to the GM HEI also. One reason the Olds people might like it could have to do "where" on the motor that their distributors are located (i.e., on the back rather than on the front). As with other GM engine families that used points and then used HEI, you'll probably need a new spark plug wire set (OEM spec pre-terminated) to match the year of the distributor and donor vehicle to complete the change.

If you are concerned about BCA judging issues (even for the Driven Class!), you might desire to consider an "incognito" upgrade to a Pertronics system. This would not significantly change the underhood "look" of the vehicle as the HEI would. Your judgment call on that!

Points can work well, provided the contact cam is not worn from miles and/or lack of lube on the rubbing block of the points. Points also have no "minimum battery voltage" issues as electronic systems can--which can relate to the vehicle not starting with a marginally weak battery with the electronic ignition vehicle, although it will spin over and has clean spark plugs. If the points will "spark" when they open or close, the spark plug will get a spark of some intensity.

In general, though, the electronic conversions can be much easier to deal with in our "no maintenance" orientations of modern times/vehicles. What type of system you decide to use CAN relate to what future uses you might have for the vehicle.

The normal HEI is a very good unit with lots of spark capacity in stock configuration--a "design" spec from back when was for it to fire a .100" spark plug gap, although it was observed that when it was over .080", plug wire condition might be an important issue. Therefore, running .035"-.045" is no problem. There's also supposed to be some variable dwell design in the factory modules too, which the aftermarket units supposedly do not have. Only issue is that potential spark output starts to decline past about 4000rpm, but I doubt that's not a "normal cruise rpm" for many of use in our normal driving situations. Even with the large reserve capacity, the "decline" might not be significant if spark plug gaps are in the more normal .035" range with a generally stock engine. Add in some of the more modern Iridium or other .040" wire electrode spark plugs (which take less juice to fire) and the "decline" can be pretty much a non-issue for the generally stock engine--plus even LESS maintenance.

Enjoy!

NTX5467

[Guest BJM]

Got the HEI distributor today. One large red wire going to it? I don't know why but I thought there would be more wiring. I have yet to inspect to see how this thing works. I suspect I will need some new parts. I like the cap that holds the plug wires in place on the distributor. The car I took it off is a 75 Limited 455 with 75,000 miles. Shaft and splines looked OK. I will sand the aluminum body, which showed corrosion. It's going on a 68 430 engine that will be heavily modified.

The 4000 rpm comment worries me a little. This 430 will be going into a car with a numerically low rear 2.56 gear but 1st gear in the TH400 is 3.00 instead of 2.45 stock. Cruising at 65 mph will probably be below 2000rpm but if I need to pass, then I expect rpm will rise to 4000 to 5000 rpm.

I don't foresee a circumstance where I go over 5000 rpm. But, new Mallory Unilite distributors for Buicks are $400 to $450. This one cost me $25.

[NTX5467]

It's not that the output past 4000rpm goes "to pot", just that it decreases from what it is at lower rpms. Still higher than what a point system would be and still most probably less of an issue with the more normal .035"-.045" plug gaps. ALSO note that HEIs were used in factory applications (i.e., Chevy L-82 Corvette motors) that were capable of well past 4000rpm engine speeds in stock form.

One book on ignitions noted long ago that all it takes to get rid of the higher rpm spark output decrease in the HEI is an MSD module for the HEI. It's pretty much a bolt-in situation, but can require some re-wiring internally as some connections are in different places from stock.

The spark plug wire retainer on the cap was on the earlier models and the spark plug wire boots at the distributor indexed with the retainer so that the whole wire set could be removed as "an assembly", but this was deleted in later models. The "pre-HEI" electronic ignition (which had limited optional availability on some 1972 Pontiac V-8s) had a similar spark plug wire holder on the cap.

The spark output of the stock HEI has been well documented over the years, but the output at lower rpm ranges proves that the basic setup if quite good in many respects. I've not seen any graphs or figures on the variable dwell situation of the stock module, though, of it is was only on the earlier modules. If you put a dwell meter on a vacuum advance point distributor and rev the motor (to get vacuum from the ported vac advance port), you'll see the dwell decrease as the vac advance works. Dwell decreases the "charge time" of the coil so ultimate coil output could similarly decrease. Perhaps having a module that has a constant dwell situation at all rpms would similarly have a higher spark output at the higher engine speeds too? Usually, after the higher output electronic ignitions came out, we didn't "need" dwell meters any more (no points to adjust, no point gaps, no maintenance--just "plug and play") and some engineers stated that although you could get a dwell reading, it would not be accurate--hence, "no worries" about those things.

In our current times of fuel "issues", using an HEI module from a middle '80s Chevy pickup and the attendant knock sensor hardware could be a good salvage yard setup to be scouting for. The knock sensor plugs into the right hand bank block drain plug and then the harness goes to a stand-alone controller and then to the "more pins" module in the distributor. They were on Chevy 305s and 350s of that era--if you find an engine with a silver dollar sized sensor with one wire coming out of it rather than the normal pipe plug in the block on the right hand side, that vehicle has the system on it, called "Electronic Spark Control". There were different part number sensors for 305s and 350s, but I don't know why other than if one needed less sensitivity than the other one. I see that MSD also has a new knock sensor system out now too.

I'd say to proceed in the direction you're headed in with the HEI conversion. It'll probably work well. DON'T forget to put the dielectric grease under the module after you get everything cleaned up and reassembled!!!! The module generates heat and the dielectric grease helps dissipate the heat (via a "heat path") through the distributor body (heat sink). If you get a new module, it should come with a small packet of said grease. As the distributor body serves as the heat dissipator of the module's generated heat, it might be adviseable to just clean it up and not make it shiney or "more pretty" than the stock appearance ("shiney" might reflect heat, but it doesn't dissipate heat nearly as well as "satin" or "dull" does).

I suspect you're also going to replace the spark plug wires. I have used magnetic suppression plug wires by Borg-Warner with great success for many 100K miles on my vehicles. I like them as they USED to be in the same colors as the factory GM wires, but had massive correct-color boots on them. They were KoolWire and KoolWire II in the earlier times. I think they are now "Select", though. There might be other companies that have them now too. They come pre-terminated so that they are direct factory replacement part. Don't be surprised if they do not have the tabs to index with the plug wire retainer of the earlier HEI plug wires--even if you get an ACDelco set of "normal" resistance wires. Magnetic suppression wires also have about 1/10th the resistance of "normal" resistance plug wires.

Just some additional thoughts. Enjoy!

NTX5467

[Guest BJM]

Thanks again for the update. For peace of mind I will probably replace all replaceable parts but there is no rush. There aren't that many $25 HEI take offs around anymore though so i am glad I got it. Checked TA Performance and the Mallory Unilites and Mallory HEI's are $400 to $450. I'll have $125 in this one. Plug wires are down the road BUT the plug wires on this car looked brand new - 8MM. I thought about taking them. Sometimes a car owner "tries" a tuneup before giving up on a car and there are all these new parts under the hood.

[NTX5467]

All of the earlier HEIs used 8mm wires as factory production, but they were the normal resistance wires.

Enjoy!

NTX5467