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To me it looks like someone converted to "pointless" ignition?
But did they convert the original distributor or is the whole distributor/ignition setup aftermarket?
It's a GM HEI (High energy ignition) GM made millions of them from the mid 70's to mid 80's. They are still produced by the aftermarket today.
You can get parts for it at any auto parts store or online automotive part sellers.
It's a complete unit and would replace an original points distributor and coil.
It's pretty much a plug and play installation into an older vehicle with the exception of the power wire. Typical GM points ignitions used a resistor wire to deliver less than 12 volts to the coil. The HEI unit requires a full 12 volts. To correct this (if it hasn't already been done) you need to replace the resistor wire with a 12 gauge wire.
It's a GM HEI (High energy ignition) GM made millions of them from the mid 70's to mid 80's. They are still produced by the aftermarket today.
You can get parts for it at any auto parts store or online automotive part sellers.
It's a complete unit and would replace an original points distributor and coil.
It's pretty much a plug and play installation into an older vehicle with the exception of the power wire. Typical GM points ignitions used a resistor wire to deliver less than 12 volts to the coil. The HEI unit requires a full 12 volts. To correct this (if it hasn't already been done) you need to replace the resistor wire with a 12 gauge wire.
Thanks.
When using rockauto.com i need to specify year, make and model.
When i type in 1972 oldsmobile cutlass supreme 350 it obviously shows me parts for the original points ignition system.
What vehicle could i shop instead that uses this HEI from the factory so i can find the right parts?
Edit:
And are the spark plug wires the same for points and hei distributor?
Last edited by Michael_; February 16th, 2023 at 01:38 PM.
Okay i did a little research and as far as i can tell 1975 this HEI became standard.
So i just shopped 1975 Oldsmobile Cutlass Supreme 350 (instead of 1972) on rockauto and now i see the right ignition parts.
I think i will go with 1975/HEI spark plug wires aswell just to be sure.
But what does this mean for spark plugs?
1975 and 1972 seem to use different spark plugs and gaps.
Having a 1972 with a 1975+ HEI Ignition which spark plugs should i run?
If it's a factory GM HEI it will have numbers stamped on the side of it that include the part number and date code that would allow you to more completely identify.
Using a 1975 Cutlass Supreme 350 to shop for parts should work just fine.
Yes, the plug wires are different between an original points cap and an HEI cap.
No, use the 1972 spark plugs as they will be the correct heat range for your engine. You can open the gap to .040" or so but it is not mandatory; it allows you to take better advantage of the higher energy that the HEI can deliver.
No, use the 1972 spark plugs as they will be the correct heat range for your engine. You can open the gap to .040" or so but it is not mandatory; it allows you to take better advantage of the higher energy that the HEI can deliver.
Great. So basically i buy everything distributor related and the spark plug wires for the 1975 model year but spark plugs for the 1972 model year.
Good to know, thanks.
The firing order of an Oldsmobile V8 is 1-8-4-3-6-5-7-2, but the wires are labelled 1-2-3-4-8-7-6-5 as the distributor turns. I cannot tell what the other end of the wire is connected to, so it is possible that it runs fine, but I would never label them this way.
The firing order of an Oldsmobile V8 is 1-8-4-3-6-5-7-2, but the wires are labelled 1-2-3-4-8-7-6-5 as the distributor turns. I cannot tell what the other end of the wire is connected to, so it is possible that it runs fine, but I would never label them this way.
It runs good but i can't tell you the logic behind that labeling.
I am not OCD, but the numbering of the spark plug wires has me shook. 😜
It made me go 😬 too.
Before you remove any plug wires from the cap, trace the #1 plug wire back from the spark plug to the cap. Mark that cap terminal "#1". That will give you a starting point when you install new parts. #1 plug is the front one on driver side of the engine.
Won't hurt to mark them all by tracing back from the plug so they can be put back in the correct order.
Run plugs at .035 and do not put them to later specs. That was only for emissions
THIS.
HEI was getting out of hand with emissions stuff by the 1980s Olds V8 engines I know were using gaps recommended at 0.060" per the initial tune-up standards and underhood labels. This put undue strain on the coils, epoxy coatings, and ignitions issues they didn't like fixing under warranty, apparently. There's some bulletins out there on this, but Chevy was a bit smarter about it, I guess because the Corvette guys screamed bloody murder. They had a campaign to actually replace the coil/ignition module and the emissions tune-up decal under the hood and to shorten the spark plug gap to 0.040" or 0.035" or something like that. Can't recall off-hand.
You can keep your original 72 gaps and plugs. Or even open them up a hair. You'll just (IMO) have a better spark with the HEI.
Ah, found it. Here it is. To note: the 1985 Corvette replacement parts were the same as the Olds V8 ignition components in 1985.
Last edited by 69HO43; February 17th, 2023 at 06:15 AM.
Only out of interest:
Do the negative side effects already come in at 0.045" gap (which a lot of people seem to run) or only at even wider gaps? Would there be any benefits in running 0.045" over 0.035" ?
I can’t address all of that, but I can say that I have gapped the plugs at .045” for 20+ years with no issues. I should also note that I have an Accel HEI SuperCoil and not a factory style coil. Dunno if that would make any difference.
I can’t address all of that, but I can say that I have gapped the plugs at .045” for 20+ years with no issues. I should also note that I have an Accel HEI SuperCoil and not a factory style coil. Dunno if that would make any difference.
Since i'm already using an HEI coil and spark plug wires i would also expect them to last using HEI specifications AKA 0.045" gap.
The AC Delco Spark Plugs i just bought are pre gapped @ 0.044" so i think about just dropping them in without regapping them.
Actually the factory gap for the early 307 was .080"! The only time we had issue was worn out plugs not starting one damp morning. Makes sense a gap close to .100" wouldn't fire! The later 307 were reduced to .060". Many of us run .045" wit HEI, myself included with zero issues. Crazy you have a different coloured rotor, cap and coil cover along with incorrectly numbered wires from the last owner. That .044" gap will work just fine.
Actually the factory gap for the early 307 was .080"! The only time we had issue was worn out plugs not starting one damp morning. Makes sense a gap close to .100" wouldn't fire! The later 307 were reduced to .060". Many of us run .045" wit HEI, myself included with zero issues.
That .044" gap will work just fine.
I think i will run them with the 0.044" pregap & if i should encounter any problems i will regap them to 0.035".
Crazy you have a different coloured rotor, cap and coil cover along with incorrectly numbered wires from the last owner.
I'm starting to think that this whole ignition might be a parts bin special. Maybe those spark plug wires have been used ones from another vehicle where that labeling made sense?
Last edited by Michael_; February 18th, 2023 at 09:11 AM.
I think i will run them with the 0.044" pregap & if i should encounter any problems i will regap them to 0.035".
I'm starting to think that this whole ignition might be a parts bin special. Maybe those spark plug wires have been used ones from another vehicle where that labeling made sense?
The advice read here to gap at .035" is correct. The weak point on these HEI systems was the wide gap caused and still causes a path of least resistance arc to ground right down through the middle of the rotor, over time this causing the mechanical advance assy to freeze up with lots of red rusty powder, for those units which actually have a mechanical advance. The factory wide plug gap spec was a service headache.
The first HEIs in 73-74 used .080 plug gaps which were quickly found to be unsustainable. Service bulletin came out in 1976 (may have been 75) instructing dealer mechanics to set the HEI plug gap at .060 which improved things but was still a lot for the HEI to fire consistently and reliably.
.040 to .045 gap has worked well for me. Makes a big fat spark but doesn't tax the system as hard as those wide gaps did.
Apparently, we didn't get that memo in Canada. The emissions sticker said .080" on my 81 Delta 88 with an Olds 307. I wonder why it wasn't changed by that point, .060" is plenty big.
Flat tappet G-body 307s got .080" specified through 1985 based on their emission/tune-up labels.
Y-roller 307s in 1985 got the .060" gap specification. Y and 9 307s started.
At some point, GM "replaced" the OE recommended R46SX spark plugs to use R46SX, which had a 0.060" gap out of the box. According to my information, GM p/n 5613881 (R46SX) plug got superseded to GM p/n 5613882 (R46SZ) sometime around 2000.
Unfortunately, the ACDelco Tune-up specifications book for 1987 (SD-100A) still showed 0.080" gaps for the R46SX recommended plugs. Yuck.
February 16th, 2023, 12:49 PM
