63_Distributor won't drop unless bumped

[Charles D.]

Re: 63_Distributor won't drop unless bumped

Steve check to see if the plastic lock on pump to shaft isn't cracked causing shaft to move to one side .

[Steve D.]

Re: 63_Distributor won't drop unless bumped

The link below is to a clip in which I attempt to show what I have been trying to explain in this thread. The intake manifold is off because I removed it to determine if it was somehow keeping the distributor from dropping; but it was not. I hope the link works.

https://youtu.be/UN6shsuiFVU

[Michael W.]

Re: 63_Distributor won't drop unless bumped

The video is marked as private.

[Steve D.]

Re: 63_Distributor won't drop unless bumped

My first effort. Let me see if I can correct that

[Steve D.]

Re: 63_Distributor won't drop unless bumped

Try it now, and please let me know if you still can't view it.

[Terry B.]

Re: 63_Distributor won't drop unless bumped

I'm apparently missing something because I don't see the problem. Distributor drops freely when bumped, so I always set the timing, tightened the clamp bolt, and drove away. What am I missing. The position of the cam and hence the distributor drive is not aligned, therefore, rotate the cam (bump the starter) and the distributor drops in place.

[Richard M.]

Re: 63_Distributor won't drop unless bumped

I've followed this thread from the beginning and just watched the video. Several replies talked about the shaft to pump alignment. I agree.

I suspect that whenever the distributor or you primer tool is removed, it is drawing the pump shaft up and away from the oil pump driven shaft via the lower mating collar. Maybe there are burrs on the distributor slot hole or shaft slot and it grabs when raising. If it raises the pump shaft up, ever so slightly, it may be rotating it off of the pump driven shaft slot and no longer aligned. If the shaft is raised from the pump, it may be preventing the distributor gear from properly aligning and dropping into position. This is because the shaft is sitting above the pump driven shaft slot. When you bump the starter it may be allowing the lower collar to then find "home" on the pump driven shaft. Turning the shaft with a long screwdriver may not allow the shaft to drop for some reason. Maybe it's slightly misaligned.

Maybe try this......

When the "no drop without starter bump" condition occurs, pull the distributor out and use a long articulating needle nose plier and reach down and carefully raise the slotted shaft a little bit and rotate it until you feel it drop onto the pump shaft. Don't raise it too much to pop the collar off. Just lightly to see if the shaft drops down when turning and if it finds home. Then try to install the distributor at all iterations to see if it drops down without a starter bump.

In summary, I agree with the consensus, and I think the main shaft is simply raising up off of the oil pump shaft and dislocating the pump shaft and collar slots every time you remove the distributor or primer tool.

This same condition happened to me on a BB distributor a while ago. The distributor would NOT drop in, in any gear position. The main shaft was slightly raised above the pump shaft. I could feel it drop down using the pliers.

Rich

[Mark E.]

Re: 63_Distributor won't drop unless bumped

I've never encountered the problem described by Rich, but that could be what's happening since he's seen it before.

My theory is that as the distributor is removed and turned by the cam gear, it also turns the oil pump shaft slightly- just enough so it won't engage when reinstalled. This usually isn't an issue, but maybe in your case the slot and tongue have a tighter than normal clearance. So another idea is to rotate the oil pump shaft slightly using a slotted screwdriver before dropping the distributor. This reorients the oil pump shaft slightly in relation to the distributor. Bumping the starter accomplishes the same thing by reorienting the distributor in relation to the oil pump shaft.

Also, remember that the "walking" technique only works after the distributor is fully dropped and engaged.

[Timothy B.]

Re: 63_Distributor won't drop unless bumped

I've never encountered the problem described by Rich, but that could be what's happening since he's seen it before.

My theory is that as the distributor is removed and turned by the cam gear, it also turns the oil pump shaft slightly- just enough so it won't engage when reinstalled. This usually isn't an issue, but maybe in your case the slot and tongue have a tighter than normal clearance. So another idea is to rotate the oil pump shaft slightly using a slotted screwdriver before dropping the distributor. This reorients the oil pump shaft slightly in relation to the distributor. Bumping the starter accomplishes the same thing by reorienting the distributor in relation to the oil pump shaft.

Also, remember that the "walking" technique only works after the distributor is fully dropped and engaged.

Mark,

Walking the distributor clockwise is done because it's NOT engaged in the oil pump drive, that's the whole reasoning behind walking it around.

[Jim D.]

Re: 63_Distributor won't drop unless bumped

Thanks for the video. I had a problem picturing what you're talking about. Your problem appears to be with the distributor gear and cam gear not "meshing" unless you bump the starter. Why? I don't know, but it has nothing to do with the oil pump shaft. Your issue presents itself long before the distributor gear is close to the oil pump drive shaft. That's an odd one for sure.
I hate problems like this. I'm having an issue with an engine that defies all logic and nobody can figure it out. This is supposed to be a fun hobby but sometimes it will drive you crazy. Good luck.

[Mark E.]

Re: 63_Distributor won't drop unless bumped

Mark,

Walking the distributor clockwise is done because it's NOT engaged in the oil pump drive, that's the whole reasoning behind walking it around.

Walking the distributor is to properly clock the distributor housing in relation to the block, not for engaging the oil pump shaft. To walk the distributor, first it must be fully installed. The distributor is then gently pulled up to disengage the cam gear while keeping the oil pump shaft engaged. This changes the clocking of the distributor housing in relation to the block without disengaging the oil pump shaft. In Corvettes clocking is especially critical because of the tach cable, and clearance between the VAC and ignition shielding hardware.

I just learned this technique from this thread, and it works great for clocking. But pulling the distributor a bit higher and walking it one cam gear tooth at a time in an attempt to engage the oil pump shaft doesn't always work. Sometimes the shaft is 1/2 tooth out of phase and needs to be aligned before dropping.

[Mark E.]

Re: 63_Distributor won't drop unless bumped

Thanks for the video. I had a problem picturing what you're talking about. Your problem appears to be with the distributor gear and cam gear not "meshing" unless you bump the starter. Why? I don't know, but it has nothing to do with the oil pump shaft. Your issue presents itself long before the distributor gear is close to the oil pump drive shaft. That's an odd one for sure.
I hate problems like this. I'm having an issue with an engine that defies all logic and nobody can figure it out. This is supposed to be a fun hobby but sometimes it will drive you crazy. Good luck.

I think there's a good chance that moving the oil pump shaft a little will allow the distributor to drop. As mentioned earlier, this effectively does the same thing that bumping the starter does.

Also mentioned earlier by another was that once the distributor drops (either by bumping the starter or other means), the problem is solved. It can then be properly clocked by "walking" it as described in the PDF.

[Jim D.]

Re: 63_Distributor won't drop unless bumped

Mark, Watch the video and look at how far the distributor drops after the starter is bumped. That's a lot more than engaging with the oil pump shaft. Also, when he removes it, watch how it turns as it disengages from the cam gear (it would already be above the oil pump shaft at this point) but it won't re-engage with the cam gear once it's been lifted. Very strange indeed.

[Timothy B.]

Re: 63_Distributor won't drop unless bumped

Steve,

I watched your video, try to work clockwise when you walk the distributor around and make sure there is some oil on the distributor lower gear. For some reason I thought of that because if it's dry for sure it will be more difficult.

That could be a aftermarket cam where the drive gear is not cut exactly or a burr at the top of the gear (more likely) causing the problem. Did you rotate the lower gear 180* and could the distributor shaft be very slightly bent and it would slide in better with the gear back where it was.

Regardless, I really don't think it will cause a problem.

[Frank D.]

Re: 63_Distributor won't drop unless bumped

I have nothing to add really - except I've 'stabbed' a LOT of distributors in cars (mostly GM) and have never encountered this....quite strange and the video is perplexing.