Looking for some advice on my distributor advance.

The weights in the distributor in my 65 L79 were not wanting to spring back when released. They also had some red residue on them. I cleaned up the weights and thought I had everything acting normal, but I pulled the rotor again after about 50 or so miles of driving and now’s it’s back acting a lot like it did when I first got the car. Wondering if I need to step up my polishing game, or if new weights are a better solution? I mostly just cleaned them off with brake cleaner and a very mild abrasive. Or could something I’m not thinking of be causing this issue? Is there some sort of recommended polishing compound?

I’ll attach a video from when I first pulled the distributor to clean, and then when it working as it should before installing back in. Seemed all good, but now acting again like the first video. Not always springing back.

 

Trying to upload a short video, but keep failing. I’ll see if I can find another way to attach.

 

Hopefully this works.

Here is how it looked when I got the car


Here it is after cleaning it up, but back to acting gummed up again.

 

Prolly not the weights at all but the center shaft sticking. Just pull the weights, springs and points off and see if the weight pins move freely.

 

That's what I ws thinking - could be one of the shaft bushings. Remove the weights as JF said and see if you feel any binding when working the shaft back and forth.

 

I agree with the others here. It appears that the distributor shaft is sticking in the housing bushing. There is a shallow "well" with a felt ring that holds lubricant under the advance mechanism that is suppose to keep the bushing lubricated. The original lubricant is probably completely dried out. If it were me (and it has been) I would remove and disassemble the distributor, clean, lubricate. You will also be able to assess the condition of the shaft and bushings and determine if they should be replaced. You can purchase rebuild kits from most of the aftermarket Corvette suppliers.

Ted

 

That's what mine did, good time to set your numbers. Bottom side has A slot to limit mechanical advance.

 

Did you inspect the pads on the advance plate and bottom of the weights for wear? Did you lubricate the pads with a thin film of grease? Did you inspect the hole in the weights and the ends of the weights for wear? Did you inspect the bushing in the advance plate for excessive lateral play indicating wear in the bushing?
Have the springs been replaced with lighter springs to obtain a different advance curve than stock?
The Chevrolet Chassis Service Manual section 6Y-18 will provide guidance in lubricating and maintenance of the advance plate and weights.
The weights don't start the mechanical advance until the engine is at a specified RPM. Example, the 66 327 mechanical advance begins at 900 rpm if the springs are factory specification. The springs resist weight movement and begin to stretch at 900 rpm. Any initial movement of the weights that does not move the advance plate around the football on the shaft does not affect this initial advance.
I have seen using lighter springs than stock will allow some of said initial movement as well as worn springs stretched by years of service.
If you put your timing light on the engine and plug the vacuum advance, you can verify the mechanical advance start at the specified RPM. You can also monitor the timing to see if the weights are sticking as the timing will not return to initial or base timing after acceleration.
If the advance weights allow the timing to return to initial timing below the specified rpm, you don't have a problem. If they are sticking, you will see it with your timing light. Of course if you have a distributor machine, it will also show if they are sticking.
Hopefully, Duke, Lars, etc. experts will provide their opinion and mine is not off in space.
Just my $.02, can't buy bubble gum with it.

 

Sounds like the consensus is to pull the dist. back out and dig deeper. Will do.

 

It could be the unit, where the weights ride, and the main shaft has some hardened grease preventing the weights from returning. See picture.
I also included my article on how to recondition the distributor.
Joe

 

Wow. That document is great. However, it makes me a little nervous that I’m over my novice skill level. I suppose I could start working through it and see if/when I get stuck. I would assume there are still folks out there that I could pay to blueprint it for me if I get way too stuck.

Probably not much more than a week or so of driving season up here in MN. The car is generally driving great so I may enjoy it as is for the next week and then start in on Winter work.

 

Not a difficult project..........unless you need to remove and replace the upper and lower bushings. This requires a bit more finesse.

But there are a few good rebuilders out there that can also do this job for reasonable $$$. We can advise if needed.

Larry

 

Happy New Year everyone. I am working through my distributor per Joes excellent write up with pictures. Now that it’s apart, I have some questions on what I need to order, and also on the lower bushing.

Here’s is what I see:

New shaft due to scoring on the bottom end

New lower bushing? I tried to get the best pic I could. If I need this, I’ll have to decide what to do as that might be out of reach for my skills

2 of the 5 shims present look discolored and feel rough. I’m assuming I should replace those?

My end play before I took it apart was .016. Do I order some extras to tighten that up some?

Do you use a new roll pin, felt washer, c clip etc? How do I know if the points need replacing. They look like the’ve been in there a while, but the car ran well before pulling the distributor.

 

Hard to tell about the shaft from pictures. I would try polishing the area with some 600 sand paper wrapped around the shaft and a shoe string or similar wrapped around the sandpaper with 3-4 loops and then pull the string ends to rotate the sandpaper back and forth. A little WD40 on the sandpaper will help lube it and not.load up. The shaft can be mounted in a padded vice to hold it. If that still leaves it looking pretty scored it may be best to source a replacement shaft if possible. Have you measured the rough shaft dimension compared to the undamaged area? When in the distributor housing does the shaft feel loose in the bushing? You can mount the housing in a padded vice and set up a dial indicator reading the shaft and check it for lateral movement. If it’s over 4-5 thousands then the bushing should be replaced.

I wouldn’t worry about the condition of the washers but I would get a distributor shim kit (Mr Gasket) and shim the end tolerance down to at least 4-5 thousand’s.

After cleaning and light lubing does the cam assembly now move smoothly on the upper shaft portion?

 

I’ll try some sandpaper and then take some measurements in shaft diameter differences. Before I disassembled it, I could not feel any side to side play. I haven’t reassembled to see how smooth it turns now, but it was pretty gummed up in there, so a cleanup was defiantly in order.

 

Getting ready to drop the distributor back in the engine. I cleaned the lower gears so they don’t have anything on them. Do add put any grease or oil on them before reinstalling?

 

I would put some oil or chassis grease on the gear, but it is probably going to get oil from the pump and be ok.

 

For a new gear install, I have always used a bit of Engine Assembly Lube. For just pulling and re-installing the distributor, I have simply used a some motor oil, FWIW.............

Larry

 

Thanks all!