General Category > Quadrajet Carb Talk and Tips
HEI Distributor mechanical advance curve options
Cadman-iac:
--- Quote from: DJD OLDS 4MC on March 16, 2026, 04:37:50 PM ---All HEI except Oldsmobile - center plate numbers and fly weight numbers face up.
Olds HEI - center plate numbers and fly weight numbers face down.
According to Dick Paterson @ Springfield Ignition, Orillia Ontario Canada
--- End quote ---
Interesting, I've been going by information I got from another site that had quoted a guy named Rocky Rotella, and it says that the factory installed the center plate with the numbers down. I kinda questioned that, since it makes it necessary to remove it to find out which one you have.
I'm guessing that the Oldsmobile goes numbers down because of the counter clockwise rotation of the distributor, which does make sense.
Before finding that article, I've always installed them numbers up,it just made better sense to me.
Another thing I've noticed too, when checking them with everything in place, there's several center plates that don't seem to work well number down, the weights didn't want to retract fully, they seemed to be flopping between the plate and what would be the normal stop point on the weight, if that makes sense.
You wouldn't happen to have a link to this Paterson guy, or the article he wrote would you? Thanks for your help, it's much appreciated.
Rick
Cadman-iac:
Pontiac also rotates counterclockwise, so wouldn't those also be installed numbers down like Oldsmobile?
I'm doing this on a Chevrolet distributor, and another one for a Cadillac that'll be used later on.
These blanket statements, both from Rocky Rotella and Dick Paterson give one reason to doubt, as there always seems to be an exception for one reason or another.
Rocky Rotella's article doesn't mention anything about direction of rotation at all, at least not in any of it that was quoted where I had found it.
As for Dick Paterson's that you mentioned, it breaks out the Oldsmobile as being different, and having had a couple, I knew of the difference. I had had a '68 Pontiac back in the 70's, but I had to think about that one before remembering that it was also counterclockwise. ( Learned that in high school after replacing the cap and plug wires one day. Didn't make note of the wire positions before yanking them off. Couldn't figure out why it kept backfiring through the carb, lol)
I have an older GM unit repair manual for the HEI distributor from around 1975 or '76, gotta look at it again to be positive. Anyway, one of the pictures does show the weights and center plate somewhat clearly, and I'd swear you could see the number on the center plate. Unfortunately it doesn't mention anything about disassembly of the shaft or the advance mechanism, it was mainly for troubleshooting the electrical portion of the distributor since at that time it was a relatively new system for most mechanics, and an overhaul of the unit shouldn't have been necessary at the time of printing.
I did Google Dick Paterson and got his website. He doesn't give much information, other than advertising for his distributors, so I'm guessing he probably doesn't just give out information free of charge.
Unfortunately, information like this will probably die with him .
It's one reason why I'd like to post what I can about it for anyone who can use it, like Cliff does here for carbs.
Rick
70GS455:
I've seen some DIY distributor machines and it didn't look all that complicated. Just a support structure, a 12 dc motor, dimmer speed control, degree wheel, tach and timing light
Cadman-iac:
--- Quote from: 70GS455 on March 18, 2026, 06:53:07 PM ---I've seen some DIY distributor machines and it didn't look all that complicated. Just a support structure, a 12 dc motor, dimmer speed control, degree wheel, tach and timing light
--- End quote ---
That's a bit more complicated than I'm ready to get into until I figure out what exactly I'm going to do.
I did a quick search for a distributor machine, not much out there, and what is is way out of my price range.
Thanks for the idea though, I may have to try that if what I'm trying now doesn't help much.
Rick
70GS455:
--- Quote from: Cadman-iac on March 21, 2026, 05:23:47 PM --- That's a bit more complicated than I'm ready to get into until I figure out what exactly I'm going to do.
I did a quick search for a distributor machine, not much out there, and what is is way out of my price range.
Thanks for the idea though, I may have to try that if what I'm trying now doesn't help much.
Rick
--- End quote ---
How about this one, a VS drill motor, vice, plastic compass, timing light
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