Help clarify harness adaptation existing HEI to OE points
I’m looking to revert back to the original points distributor in my 72 Blazer. The engine harness is an American Autowire example made for use with an HEI distributor. Am thinking the hot wire to the distributor will require modification with use of a connector that jives with the OE type threaded post on the external coil.
Am I thinking correctly? If so, is there an adaptive connector by chance that I can screw into place on the external coil and plug the existing HEI connector on to without modifying the harness at all? Here’s what AAW claims: “This harness is modified for a 12 volt HEI ignition. We replace the original resistor wire with a standard 12 volt feed, and will include a connector for a GM large cap distributor. If you are not using a GM large cap HEI distributor, the connector end may need to be replaced to connect to your system.” Thanks. |
Re: Help clarify harness adaptation existing HEI to OE points
You should remove the HEI wire from the harness, and add a resistor wire that goes part way to the engine, and resumes in 2 yellow wires that go to the starter R terminal and the coil. You would probably be able to get that wire from another member by posting a want-to-buy ad in the parts section, or dig it out of your stash if you have the original harness. Harnesses can be unwrapped and re-wrapped because they usually have non-adhesive vinyl tape.
This is the wire you would be putting in. The junction shown by the dot is inside the wire harness before it gets to the end of the wrap that attaches to the engine at the transmission bell housing wire clamp. https://67-72chevytrucks.com/vboard/...1&d=1465078686 It is the white cloth-covered resistor wire that you would use to replace the wire at your firewall plug, you may have a pink wire there now. https://67-72chevytrucks.com/vboard/...1&d=1465078686 Squeeze the terminal like this to release it from the connector. https://67-72chevytrucks.com/vboard/...1&d=1465079038 You'd be doing the opposite of this job, where if you had an orginal harness replacing a points distributor resistor wire with an HEI wire. https://67-72chevytrucks.com/vboard/...d.php?t=708975 |
Re: Help clarify harness adaptation existing HEI to OE points
Here is one thread that has a diagram.
Link: https://67-72chevytrucks.com/vboard/....php?p=9061422 Hope this helps. |
Re: Help clarify harness adaptation existing HEI to OE points
The alternative is you can cut your HEI power supply wire, and install a ballast resistor which you would mount on the firewall, change the terminal on the end to the ring terminal to fit on the coil, and run another wire with ring terminals on both ends to the coil and the R terminal on the starter. The ballast resistor or resistor wire reduce the voltage at the coil to preserve the coil and your points. The additional wire going to the R terminal on the starter is to bypass the resistor and provide full voltage to the coil only during start, to give a bigger spark during start.
|
Re: Help clarify harness adaptation existing HEI to OE points
Guys thanks a ton for the replies. I’ll contact AAW and see if they have a schematic of their HEI engine harness.
Was hoping it would be more straightforward like a cut-then-crimp on OE coil connector to the existing harness HEI end. Sounds like doing so would result in electrical failure. Stupid me, I assumed the harness were the same except for something like a packard style connector at the HEI rather than a ring or C clamp connector for an external coil. I’ve got spare OE harnesses that I can poach from at least. Tempted |
Re: Help clarify harness adaptation existing HEI to OE points
I don't think it would be all that bad. This is the HEI diagram you would be converting from. Here the wire is pink, not sure what color AAW would have picked.
https://i.imgur.com/n4ZGNrw.png |
Re: Help clarify harness adaptation existing HEI to OE points
1 Attachment(s)
There are several ways to do what you want depending on how factory you want the truck to look.
Replace the HEI harness with a points harness. This would be the factory correct style. Or disconnect the HEI power from the firewall connector and add a new ballast wire to the existing harness. If you remove the HEI wire and re-wrap the new ballast wire with the correct harness wrap tape it would be the correct factory style. Or add a ballast resistor to the end of the existing HEI power wire and run a new wire from the other connection on the resistor to your new coil. Mounting the resistor on the coil is a convenient way to do this. See photo. The ballast resistor in the photo has the flat terminal adapter that should allow your current HEI wire to hook right up. Or leave the underhood wiring as it is and put the ballast resistor under the dash splicing the resistor into the ignition power wire from the ignition switch. |
Re: Help clarify harness adaptation existing HEI to OE points
Or you could replace the coil with an IC14SB coil from napa. It does not need an external resister.
That would be the way I would do it , I dislike the porcelain resisters as they are prone to be a problem down the road. David |
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
|
Re: Help clarify harness adaptation existing HEI to OE points
Great help all.
That external coil might be the simplest means. I’ll cross reference that number and see what’s the best quality example on RockAuto but it may be that very NAPA item. If I go with an inline ballast resistor, can you recommend what I need? I imagine the resistance varies and I want to ensure the correct example is in place. |
Re: Help clarify harness adaptation existing HEI to OE points
IC14SB coil as working without resistor is interesting, I didn't know there was such a thing. I find nothing really technical when searching on the web, just forum posts and some pictures of it from different angles than on NAPA's website showing an imprint on the side about no resistor required. So this seems to be something NAPA would rather not mention.
|
Re: Help clarify harness adaptation existing HEI to OE points
I have used hundreds of them over the years, no problems at all. I use to use the Ecklin coils before they got sooo pricey
https://www.ebay.com/itm/16654367590...3ABFBMlI35mLNj |
Re: Help clarify harness adaptation existing HEI to OE points
That is a good price
|
Re: Help clarify harness adaptation existing HEI to OE points
I pay that for the IC14SB ones That are imported
|
Re: Help clarify harness adaptation existing HEI to OE points
Great info, I think I'll bookmark this thread.
|
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
Not the much higher for the coil I dont have stock in the co, lol Just trying to help |
Re: Help clarify harness adaptation existing HEI to OE points
This article should help. Basically the difference between 6v coil or a 12 volt coil is what the internal ohm reading of the primary coil windings are. All this confusion started when the automobile went from 6 volts to 12 volts. Instead of making a different coil the manufactures for the most part added resistance to the ignition wire to drop the voltage to the coil. It was cheaper than engineering a new coil and any old coil would work on any car. Plus there was an advantage just down the road.
About the same time engine compression was increasing. The increase in compression lead to more of a voltage drop when cranking the engine over. That voltage drop caused the volt to the coil to drop and in turn the coil putout became weak and the engine was harder to start. To compensate for this the manufactures bypassed the resistor while the starter was cranking so the voltage at the coil was enough to provide strong spark. https://blog.simonbbc.com/ballast-re...nce-and-coils/ |
Re: Help clarify harness adaptation existing HEI to OE points
That is correct, most coils have 2 oms of resistance the but in these ones have from 3 to 4 oms
This is also the type coil you would need if you put a Pertronix electronic ign in |
Re: Help clarify harness adaptation existing HEI to OE points
5 Attachment(s)
Just got back from Napa with the coil. Shocked that one was in stock and grateful to have but will work real hard to discover one that is not made in the PRC. The parts guy says Echlin has a version of IC14 (no SB) that might not be PRC made but unsure whether or not it needs external resistance.
Happy to report the cap is US made and uses brass not aluminum. The gasket is US made. Advanced Distributors in Shakopee, MN is rebuilding the points distributor that’s original to the engine. I’ll ask the owner what he recommends for points and rotor. Good thread guys, I’ve learned a lot so far. |
Re: Help clarify harness adaptation existing HEI to OE points
All of Ecklin use to be made in the USA now some of it is made in Mexico The last Ecklin points I bought were made in USA
|
Re: Help clarify harness adaptation existing HEI to OE points
1 Attachment(s)
I’ll post back what I discover. Another local Napa has that Echlin example in stock (allegedly) and I’ll call about it tomorrow. Will also call Wells tomorrow and inquire where theirs is made. NGK has one too I’ll look more into.
Thinking this spade adapter might be useful and spare me from splicing in a ring terminal at the coil. |
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
|
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
|
Re: Help clarify harness adaptation existing HEI to OE points
Here's a Delco parts list for use with a points distributor I'm posting from member 1970CSTBlazer:
"I just rebuilt the original points distributor for my 1970. Here is a list of genuine USA made NOS Delco parts I used to bring it back: List is for 1972 350 Blazer: Cap: D308R/ 12338667 OR 1971244 Rotor: D409/1932015 The light duty rotor D426R 1852722 is an option, but I never liked them. Points: D106P/1931988 Condenser: D204/1932004 Uniset points/condenser: D1007 1876600 Vacuum advance can: 1973437 Coil: D512/1115238" |
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
|
Re: Help clarify harness adaptation existing HEI to OE points
4 Attachment(s)
Quick update. Yesterday I dropped in the OEM, rebuilt points distributor from Advanced Distributors. I think it’s clocked appropriately.
The internally regulated coil diameter is slightly larger than an OE example but fits in the OEM bracket although I had to use a #8 bolt and nut to secure it instead of the larger diameter original screw. If I get time today I’ll run the new plug wires. |
Re: Help clarify harness adaptation existing HEI to OE points
OK, so is it the IC12SB coil that one would use with the resistor and bypass wires?
|
Re: Help clarify harness adaptation existing HEI to OE points
Quote:
|
Re: Help clarify harness adaptation existing HEI to OE points
Well I think that is the one we just discussed using without resistor wire and without bypass wire.
|
Re: Help clarify harness adaptation existing HEI to OE points
Adjusted the timing to 18 btdc and went on a brief drive. Idles smoother than ever and there’s no hesitation. Very pleased at the moment.
Thank you for all the help! |
Re: Help clarify harness adaptation existing HEI to OE points
I had similar results when I switched the Pro Billet MSD distributor out for a correct distributor for my 1972 Cheyenne 402. The truck has a lot more pep and idled smoother.
The few downsides to points are the occasional rubbing block and contact wear. For as little as mine are driven, it will be years before they need a tune up. Using USA made old issue parts does make a difference, and also using the proper distributor cam lube. |
Re: Help clarify harness adaptation existing HEI to OE points
I'm with you. For the amount of driving I'll do this is a good way to go in. In fact, I'm tempted to swap out the HEI in the K20 but that hasn't given me any issues. I will send another points distributor off for a rebuild and keep that on the spare parts shelf. Maybe that'll be a project for next winter. The builder made some advance curve and weight adjustments to this one and remarked that it will will perform better than the "truck distributor" GM supplied.
The USA made plug wires from Lectric Limited are a real nice product and are cut to match a 4wd 350 engine HERE. At least right now, it's not difficult to cobble together (nearly) all US made ignition products. There's a guy here in WI selling reproduced copper terminal caps and black D409-style rotors (rotor is in the above photo) both of which are solid. NOS/NORS examples can still be had too. The Echlin NAPA IC14 coil is made in Mexico and I did install it after returning the PRC-made IC14SB. I wasn't able to source a US coil. |
All times are GMT -4. The time now is 12:25 AM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com