Disassembling a SC Distributor

BradH · 07-30-2003, 01:48 PM

During the PPI on my car, the tech noted that he thought the distributor weights were sticking, causing a higher than spec idle once the engine was warm and had been reved. I adjusted the idle down manually, but the problem has been creeping back lately, so I decided to remove the distributor and check it out.

I have the distributor out of the car, but for the life of me, I can't figure out how to get it apart. I removed the circlip at the top of the shaft, but the spider-looking thing on the top of the assembly won't budge. Is this part supposed to come off? How do I disconnect the vacuum advance arm that attaches to something inside the distributor body? This doesn't look that hard, but the dang thing just won't come apart! Any ideas? Am I going to risk breaking something expensive if I continue?

Thanks,

Brad
'83 SC Coupe

JK-81SC · 07-30-2003, 03:16 PM

Do some archive searching to help you out. I took apart mine a few months ago, so I'm trying to remember. I attacked the distributor from both the top and bottom. Don't break anything, since parts are hard to find. The whole thing comes apart by removing 3 screws and the gear on the bottom, if I'm remembering correctly.

To remove the vacuum module, remove the screw(s) holding it to the housing. Then the vacuum module comes off once you lift the arm going into the distributor off of a pin. Use a flashlight to look into the distributor through the slot in the side of the housing. You should be able to see the arm and pin.

There are 3 screws that need to be removed from the top of the distributor. Look for the cutouts at the edge to gain access to the screws. The spider-looking thing is held in place with a very small dowel pin that lines up with a vertical groove. You don't need to remove it in most cases. Be very careful with the magnetic coil assembly under the spider. It has very fine wires in it, and if you break the coil you might not be able to find a replacement.

On the bottom of the distributor is a steel pin that is a press fit into the shaft. The pin holds the gear onto the shaft. I had to drill out the pin to get the gear off. Once the gear is removed the entire assembly comes out of the distributor housing. Keep careful notes of the stack-up of the shims once the gear comes off. My distributor was a mess inside. I had 20 years of dirt and grime, and magnetic particles had come off of the coil.

I cleaned up the mechanical weights and re-oiled the moving parts with 3-in-1 oil. I had to make a new pin to replace the one I drilled out. I used a roll pin, filed down to the correct diameter. There are some very knowledgeable distributor people out there, and the archives should give you all the info you need. Search for posts from Early_S_Man, Superman or JDub.

Good luck,

Jeff

BradH · 07-30-2003, 05:55 PM

Jeff,

Thanks for the thorough reply. I unscrewed the vacuum advance as you advised, and see where the arm attaches to the baseplate. I've tried prying it off of its attachment, but it appears to be riveted on there. Any ideas? Was yours difficult to remove?

Thanks,

Brad

Kemo · 07-30-2003, 06:41 PM

i was able to pry up the TOP spider part using 2 screw drivers 180 deg apart. it is a tight fit for that piece, so trying to pry on one side only wont work. once you get that part off, you will be able to get down into the area where the mechanical advance mechanism is. BTW, my distributor does not have a vacume advance, so im hoping this info is correct for yours. you will see down in there how the internals of the advance unit works. there should be two springs, one small one and one slightly larger. The way i remember/understand it, is that one of the springs is for lower rpm advance and the other is for higher. In any event, just know that they are NOT supposed to be the same size. My distributor was completely siezed from rust. From a cost perspective, I had nothing to lose by opening it up. Of course I didnt know how bad the rust was until i got down into it. I used some sand paper and a dremel to smooth out the bottom part and I used a real light coat of marine grease to lube it. My car ran great after that since the advance finally started working and I was able to set it up right. My car seemed to run best at 7 deg BTDC. Prior to that, I had never opened up a distributor. If I can do it, i am sure you can. Just make sure you dont force anything and you should be fine. I was able to do mine without removing the gear pin at the bottom, maybe you can too. Post some pics and good luck.

JK-81SC · 07-31-2003, 07:06 AM

Brad,

Once I took the screws off the vacuum advance, mine came off with no trouble. Maybe someone with an '83 can jump in, since I don't know if the '83 is different than the '81 I was working. Is there any way you can take a picture of yours? The vac advance arm just slid up off of the pin, no retention of any kind on mine.

Kemo's right about the top spider. You have a choice in how far you want to disassemble the distributor. Take off the top spider and work from the top, or drill out the pin on the gear shaft, remove the 3 hidden screws and the whole thing comes apart. Mine had magnet chunks everywhere, so I was forced to do the whole tear down.

Jdub · 07-31-2003, 07:16 AM

The vacuum advance pod can be removed by tilting the unit up in a pretty sharp angle. This causes the arm from the pod to disengage from the bottom of the advance mechanism. If yours is somehow on tightly (rivet would be very odd...) then you'll need to first drill/press out the pinion gear pin, remove those three recessed screws, then move the internals up as you "break" the pod arm from the mech. adv. pin.

I did not remove the spider - no need because there isn't much I can do to these windings. As is described above you can get to most everything without removing the spider.

The pin, just FYI, does not act as a shear item that must shear should the pinion-to-crankshaft lock for some reason (God forbid). This means you can use about anything. I went to Home Depot and purchase several alternatives. I ended up finding the perfect fit using a chain link section, but one roll pin, into which you can insert a second, was a worth alternative. The pin does need to be locked to the pinion by centerpunching the pin at the edges. This is just insurance - if the pin fits tightly it probably won't slide out and into the bottom end.

John