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Old 06-16-2018, 11:22 PM   #4
hatzie
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Join Date: Oct 2008
Location: Wentworth, NH
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Re: Re Curving the Proform Distributor Timing Advance

I buy the recurve kits for the springs and plastic bushings. I leave the GM weights in the distributor.

It ain't rocket science to rebuild the stock GM HEI distributors. If the aftermarket housings and shafts are any good you should be able to install GM electrical parts in/on them.

Get quality GM OEM supplier electrical parts... Delphi and AC Delco.

Make sure the end play between the drive gear and the housing is as close to 0.015" as you can get it. Spec is 0.010" - 0.020". Shim kits from Moroso etc are inexpensive.

I posted a howto on another board...

Re-working with AC Delco & Delphi HEI electrical parts and Moroso or Accel or ... mechanical bits is not any more expensive than the cheap Asian knockoff distributors.
Cheap Chinese electrical parts are usually miserable excuses for parts. Delco and a few others have the resources to ride the manufacturers like a $2 horse so they get a quality product. The Chinese manufacturers then sell the rejects to the second and third tier outfits.
If you use quality internals then you'll have a good working distributor that'll last instead of one made from floor sweepings.

Electrical
AC Delco Professional D221 Module pigtail and condenser $15-$20
AC Delco Professional D1906 or Delphi DS10071 four terminal Ignition module $20-$35
AC Delco Professional D1907X Pickup coil for V8 $40-$45
AC Delco Professional D504A Ignition Coil $55-$70
MSD 8416 Brass contact Cap & Rotor kit $30-$40. Red MSD equivalent to the no longer made Standard Blue Streak DR450X cap and Standard Blue Streak DR318 rotor.

If you need them...
MSD 8402 HEI coil dust cover
Standard 6800R Spark plug wire retaining ring
AC Delco-1965864 Distributor shaft drive gear washer with tangs (If yours is missing)
AC Delco-1977937 Distributor shaft drive gear washer without tangs (If yours is missing)
Accel 170072 is a nice foolproof BAT and TACH connector. I'd use one of them if your 40-year-old BAT connector is hammered. You can extract the Packard 56 terminal from the stock BAT connector and the Accel plug and then insert the vehicle wire terminal in the Accel connector. If you don't have a tach just put some heatshrink over the end of the tach wire to cover the open copper end or remove the tach terminal completely from the Accel plug.

Mechanical
AC-Delco 456652 Distributor gear spring roll pin.
Standard Motor Products DG53 or NAPA Echlin ECH DP110 Grease well felt @ $10
AC Delco 1950569 Grease well felt plastic cover ***Obsolete*** If you can't find one and yours is damaged you can likely get away with just using the felt to cover the grease well.
Moroso 26140 Distributor gear shim kit around $9
Moroso 26150 Distributor body shim kit around $9
MrGasket 929G or MSD 8428 advance kit... I usually use springs, E-Clips, and plastic bushings from these kits with the original weights... Usually costs around $10
Accel 31035 Adjustable Vaccum Advance Can... Around $15-$20. BTW If your original advance can isn't leaking then don't replace it... You'll usually be better off with the old part.

Axle grease for the grease pocket at the top of the shaft.

Disassemble the distributor. I don't agree with his assessment of aftermarket coils and modules. It might've been true in the 70's but by the 1980's GM did some work on the ignition coil and module. Delco and Delphi electrical parts will be reliable for a long long time. Most of us are not driving race engines at over 5,000 RPM... more like 2,000-4,000.
http://www.rustynutscarclub.com/HEI.htm

DO NOT LOSE the thrust washer on top of the housing bushing between the bushing and the lower half of the mechanical advance mechanism.
Shown here stuck to the pickup tooth above the snap-ring. I've never needed a pickup coil so I'm not sure if the new coil has a snap ring or not. I'd be careful to not lose or damage the original.

If the bushings or shaft are scored, the bushing is worn into or past the snap ring groove, or the lower advance is seized to the shaft, get another core.

Take a picture or write down whether the advance weight ID stamps are up or down.

Clean the hard parts that you'll be re-using.
I usually blast the body with walnut shell after a dunk and scrub in Kerosene using a bottle brush and plastic bristle scrub brush. I leave it for a couple hours in the sun to dry before it goes in the cabinet. Stuff a cork or Kleenex/TP in the shaft holes to protect the bushings and rinse again with kerosene and a bottle brush and plastic bristle scrub brush when you're done.
The advance weight assembly usually cleans up by hand with Scotchbrite, a toothbrush, and kerosene even when it's rusty.
Any varnish will clean right off the shaft with Kerosene and careful scrub with a toothbrush.
I grease the rotor mount bushing with a thin layer of heavy grease on the distributor shaft.
The cam mating gear, thrust washer, and the shims usually just get a rinse in Kerosene and a dip in motor oil. If the thrust washer is missing get a replacement.

Make sure to replace the crusty grease in the wells under the pickup coil with some high temp heavy grease. There should be a plastic grease well cover and a felt ring. I just fill the wells and put the original back if it's not falling apart and nasty. My distributors didn't look like they'd been on the bottom of the ocean. If you can clean up one of those distributors... I'd put a brandy new NAPA felt in place.

DO NOT REUSE THE DRIVE GEAR ROLL PIN!!!!. The correct replacement is AC-Delco 456652.

You want the gap between the gear and the distributor body to be 0.010" to 0.020"... closer to 0.015" is better. I usually find the end play to be well out of spec. A wider gap will cause erratic ignition timing. This simple setup check causes a lot more trouble than it's worth if it's skipped.
The shim pak starts with the 1965864 tang washer, then shims, then the gear. Don't put the shims directly against the housing.

I've had distributors ride tight against the oil pump... usually with aftermarket intake manifolds. Shim between the distributor and the intake to lift the distributor body til it doesn't hit the oil pump drive. It's supposed to drive the oil pump not push down on the pump drive rod. Spec is something like 0.030" to 0.040". I usually go with "It doesn't push down against the oil pump drive anymore."

If the heatsink paste included with the module isn't in good shape or there's not enough to coat the whole module and mounting pad I use CPU Heatsink paste. I have a tube of Dow 340 Silicone Heatsink Compound that I used on the PMD on my DS4 Injection pump. The DOW 340 paste works great on HEI ignition modules. 3 oz tubes of SuperLube 98003 Silicone Heatsink paste will work fine and are around $6. Whatever you do DO NOT USE DIELECTRIC GREASE it's not thermally conductive enough.

When you assemble the coil and cap;
Be sure to put di-electric grease on the rubber washer but don't get it on the button or the coil contact... usually a pak is in the package with a new Delco coil.
Be sure the coil screws aren't too long or short to tightly cinch the coil to the cap... these should come in the package with a new Delco coil.
Be sure the stamped ground terminal makes good tight contact with the laminated iron transformer core plates.

More large cap HEI re-building info from the Corvette guys at Super Chevy...
http://www.superchevy.com/how-to/130...e-distributor/
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 04-10-2022 at 01:23 PM.
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