SC Distributor advance

[boxer246]

Having some running issues with my '83 SC motor in a '75.

I jumped the gun and bought a new MSD ignition and Blaster coil as a result of thinking my CDI was bad.....after installing, still not working, thus discovered the notorious failed Green wire coming from the distributor (actually someone had poorly repaired it and it was shorting out). SO I temporarily (until I get the correct new green wire in the mail) made a couple of shielded connectors to put the two green wires back in place. Voila!! It started right up and ran beautifully.

But, after taking the car around the block several times, the idle crept up, and it began to run more poorly. I checked the timing with a strobe light, and found the idle timing to be way too advanced. So I backed it off until it was all the way at the end of the adjustment on the distributor, and the Z1 mark was just barely in line with the mark. However, upon revving the motor (it is now backfiring and running poorly) the timing barely advanced at all. Certainly not to the 30 deg mark or anywhere near it.

BTW this is a hot high compression motor and the distributor does not have the vacuum advance, it has the little block-off plate where that would normally be.

So I guess the question is, is it possible the advance mechanism inside the distributor is hanging up or sticking? Is it a mechanical advance mechanism inside there that can be disassembled and cleaned/lubed? All the info and photos im finding of distributor repair is the ones with the vacuum advance.

[Walt Fricke]

You will find all you need by using the search function. Don't be put off by the fact that you have ditched the vacuum function. Vacuum doesn't do anything at WOT, which is what you are aiming for.

You can deal some with a high idle by futzing with the air bypass screw. I'd use that rather than distributor advance to keep the hot idle where you want it.

Yes, the centrifugal advance parts can stick. Pull the cap and see how it feels to rotate the rotor - especially counterclockwise, which would be advance. I felt a sort of hitch in mine, which was reducing the high rpm advance enough to make the motor run rough.

Pull the rotor, and pluck out the felt plug inside the shaft. Put some oil in there and put the rotor back on and work it back and forth until the hitch goes away. You can also spray some light grease in through the inspection hole (oval plug), and by removing the block-off plate from where the vacuum pot was. If you have removed the distributor to do this, you can feel for rough spots while rotating it by its gear. You can also check for sideways play both up top and down by the gear. Play = worn bearings. In addition, check for end play. There should be very little.

************ sells a variety of distributor repair parts. Kurt I a wealth of knowledge on this score.

[boxer246]

Awesome Walt thank you. Yes I did feel a sort of pulsing type of slight resistance when rotating it, but I thought that was from the mag pickup coil or something. I will try the lube. I already took the distributor out so I can work on it on the bench. I will probably just wait until that new green wire comes in until I get too carried away worrying whats going on.

It just seemed wierd that I directly after I temporarily fixed the "green" wires, the car ran super.....then deteriorated.

[sc_rufctr]

ALSO...Check you MSD wiring. I had to reverse the trigger wiring on mine to get it to run right in my 78SC. When I first installed it I got a very high idle with popping and backfiring.

Once I reversed the trigger wires it worked fine.

This is a picture of my car. If you look closely you'll note the trigger wires are reversed (purple to green etc). I did this by swapping the two leads in the plug.
(This was a temporary measure so I could get it running and tested)

[jason2guy]

if youre at the end of the adjustment, you might be a tooth off.
id pull it apart. trickiest part is getting the gear off without screwing it up. a small grinding disc on a dremel worked for me. partsklasik has a bunch of unobtainium distributor parts, in case you need stuff

[Walt Fricke]

The pulsing you felt when rotating the whole distributor shaft is doubtless the magnets and the six pointy things.

You have to hold the shaft (by its gear on the bottom) and then rotate the rotor counterclockwise to feel if the advance is sticking. It won't go far no matter what, but if you feel any sticking that can greatly affect performance.

[boxer246]

All good tips....understood.
Jason....when you say a tooth off, your not referring to the drive gear are you? Because thats pinned in place I think.
Or are you talking about the spider looking rotor?

[Jdub]

He is talking about the toothed pinion at the other end of your dist. This pinion rides on the end of your cam, and might require a reset by a single tooth. When you pull your distributor, you will turn the pinion while holding the dist. body, feeling the notchy effect of magnets and spider, and get a sense of the smoothness of the advance.

I cannot tell you what a great fix it is to just pull the dist. and clean it. You will cry when you see all of the detris and crap that has accumulated in the dist. body, preventing smooth operation and causing the car to suffer overall. SUCH a cheap fix for such an important item. Again, Partsklasik will have the small pin you will be driving out of the pinion to remove the dist guts from the top.

[T77911S]

the wires from the dist to the MSD need to be swapped. the signal is "up side down" going to the MSD.

although i find it odd that it did not run like that as soon as you started it the first time. like rufctr said, it should run bad as soon as it is started.

[boxer246]

So the purple wire from the MSD should go to the green trigger wire, and the green wire should go to the shielded wire? Not what the MSD manual says.

Today I took the distributor apart, and cleaned the advance mechanism, which was fairly sticky, with some old grease and whatever. I;ll have to wait till Sunday to reinstall it and try it. One thing I noticed though, when the rotor is lined up with the little line mark (for #1 cylinder) on the rim of the distributor, the "spider" rotor fingers are not lined up with their respective posts. Seemed odd. I'm going to try and take a pic to show that.

[boxer246]

[Flat6pac]

That outer ring with fingers up should have 30 to 40 degrees of rotation with the vacuum pod off.
Bruce

[boxer246]

Uhhh, OK, so your saying that outer ring should rotate? I pulled that off along with the mag pickup, to access the advance flyweights to lube them. I saw no indication that ring moves. Maybe it is stuck and I didnt dig deep enough into the distributor. That would certainly explain the fingers not lining up when the rotor points to the line on the distributor, right?

[hdrockerroller]

+1 on checking the trigger polarity.
hooked up one way I got a very high idle and it just did not run right. Reversed the wires to the distributor and it ran fine.

[boxer246]

My understanding is that when the vacuum advance mechanism is removed usually for purposes of switching from CIS to carbs, the stator plate should be "locked down". If it is not, then it would be free to rotate back and forth, since the vacuum advance arm is no longer locating it in a fixed position.

So with mine, the stator plate appears to be locked in a fixed position, thus allowing access to the three Phillips head screws that attach it to the distributor body.

So is it in the wrong position? Since when the rotor is pointing to #1 plug wire, the trigger rotor and stator "fingers" are not aligned.??

[sc_rufctr]

You're over thinking this. Please reassemble your dizzy and reverse the MSD trigger wires and report back.

[boxer246]

I hope your right I probably am.
I've got the distributor back together already, I'll put it back in on Sunday and see what it does with the wires reversed. Waiting for the new "green" distributor wire to come in the mail.

[boxer246]

Well I installed the distributor, and started it up, it ran better, and seemed to advance a little smoother. But, to get the 5deg BTDC mark nearly lined up, it again took virtually all of the adjustment in one direction of the distributor.

I put it at about 10deg BTDC, seems to run the best there, the motor is very cammy and high compression so I dont know what would be the correct setting.

I did switch the purple and green wires to the distrributor and it ran very very poorly so I switched that back to like it was.

There were other issues, however, that I spent a good 8 or ten hours getting straight.....all with the carbs and fuel pressure. I have the original CIS fuel pump, so I installed a PMO fuel pressure regulator, in place of the Mallory pressure regulator that was installed. Unfortunately, with the regulator dialed all the way out, 6psi was as low as I could get it. So, I installed the Mallory regulator back inline in front of the PMO, and using both, I could get the pressure down to 3psi.

After that, I adjusted fuel levels in bowls (they were way off), Then did a complete carb adjustment, which were also way off....plus I had three clogged idle jets, which, until I realized it, made adjusting the carbs impossible obviously.
I found a few other issues that I corrected like a leaky cap for the float needle, no O-rings on the idle jets, one gasket missing on the top of the right carb, under the air filter body, etc.

Now, the car runs awesome! I still have some work to do on the timing I think, as it pops through the exhaust alot when you let off the throttle coming to a stop. But the carburation is excellent, and it feels great. Now time to address the balky shifting

If anyone has some ideas on the PMO regulator issue, I'd like to hear it. Seems silly to have two regulators inline, especially since the PMO is designed for exactly the configuration I'm using it. And, before anyone asks, yes I did check that the return fuel line to the tank is clear....blew back through it with air line, and seems fine. I understand a blocked return line can cause too high pressure even with the PMO regulator. Who knows, I may just have to ditch the CIS pump and just go to a low pressure pump.

[T77911S]

your pic does not look right. the fingers need to be closer.
you need to look into the outer ring. without the vac pod on there that ring can move around.
if your timing started to advance slowly after you drove it, it could be the ring moving.
of your dist is CCW, it looks like the timing is already advanced.

as far as the wiring:
with the dist installled like it should be, with the rotor "close" to the mark on the dist. if you start the car and the timing is close, the wiring is coorect. if it is really advanced and you need to remove the dist to set it right, the wiring is wrong.
if the timing at the advance mark is correct and the timing at idle is waaay off, the wiring is wrong.
(i have only looked at the signal from the 930 dist. (CCW). i dont know if the SC would be different. the wires HAVE to be swappe on the 930.)

[wolds]

The post is correct. I replaced my Permatune last year with an MSD and went color to color as the MSD manual outlined. It is not correct for our application. They need to be swapped. Green to purple, purple to green.

Originally Posted by boxer246

So the purple wire from the MSD should go to the green trigger wire, and the green wire should go to the shielded wire? Not what the MSD manual says.

Today I took the distributor apart, and cleaned the advance mechanism, which was fairly sticky, with some old grease and whatever. I;ll have to wait till Sunday to reinstall it and try it. One thing I noticed though, when the rotor is lined up with the little line mark (for #1 cylinder) on the rim of the distributor, the "spider" rotor fingers are not lined up with their respective posts. Seemed odd. I'm going to try and take a pic to show that.