63_Distributor won't drop unless bumped

[Steve D.]

In another post, I related a vacuum leak saga. To cure that I pulled the intake and reseated it. I marked the distributor, but when I wen to replace it I could not get it to drop all the way in. It will however drop in if I bump the starter. It is not in a bind, because I can easily remove it; but once the gear clears the cam if I try to set it back down, it will not go all the way. The only thing that has changed is that the intake was pulled and re-installed, so the only thing I can thing of is that the geometry has changed very slightly. I loosened the intake bolts and tapped the intake, trying to tweak it enough make it drop on it's own, but without success. Is there a known condition causes this result?

[Mark E.]

Re: 63_Distributor won't drop unless bumped

Steve,

The distributor will only drop its final 3/4" if the slot at the top of the oil pump shaft is aligned with the blade at the end of the distributor shaft. If the engine and oil pump shaft were not disturbed since the distributor was removed, then the dist. should go right in. If not, try clocking the distributor one tooth clockwise or counterclockwise. If it still doesn't go in, then you'll need to turn the oil pump shaft as needed to align with the distributor. Use a large, long slotted screwdriver for this.

[Terry B.]

Re: 63_Distributor won't drop unless bumped

What you are experiencing is perfectly normal per my past distributor installations. The pump drive and the distributor pin are mating and hence the distributor drops the remaining maybe 3/8 inch. Usually I have someone bump the starter with the ignition key and I just apply slight down pressure and it drops into place. If you can't get the vacuum advance can to set correctly, then you may have to raise the distributor just enough to move it one tooth and again bump the starter to get it to fall into place.
Hope this helps.

[Timothy B.]

Re: 63_Distributor won't drop unless bumped

Steve,

What's happening is the gears turned on the oil pump just because the distributor shaft is removed and not holding them still. What you can do without bumping the starter is to turn the distributor clockwise until the shaft finds the oil pump slot and then walk it clockwise back around to the correct gear position.

The pump shaft will move around with the distributor shaft and keep the slot in line until you get to the correct position, no need to bump the starter. What you are experiencing is normal when a distributor is removed and you can walk it around in less than a minute to the correct position.

I hope the car runs better.

[Steve D.]

Re: 63_Distributor won't drop unless bumped

I don't think that the oil pump slot alignment is not the problem. My usual procedure is to adjust the alignment of the slot on the oil pump shaft with my marked primer tool so that the distributor will turn and drop in the right position. But something is different this time. As I mentioned above, I can easily lift the distributor up , and watch the rotor turn counterclockwise as the distributor gear pulls past the cam gear, but then if I try immediately to set it back down, it will not reseat. And no matter what position I turn the rotor to, it still will not drop (unless I bump it). I have had the distributor in and out lots of times over the years and have not run in to this before.

[Steve D.]

Re: 63_Distributor won't drop unless bumped

Tim,

Thanks for the good wishes. The problem is that manually I cannot get the distributor to drop (i.e. have the dist shaft blade slip into the oil pump shaft slot) in any position. In your note above, I don't understand what you mean by "walking" the distributor after the dist shaft engages the oil pump shaft slot. At that point, isn't the dist gear engaged with the cam gear and the distributor is unable to turn unless the cam turns?

[Frank D.]

Re: 63_Distributor won't drop unless bumped

"Bumping" and "aligning" the oil drive gear aren't necessary. It is quite easy to "walk the distributor" parts into position as Lars describes in this article. Too darn easy and the only way I do it. Steps 4 and 5 in the attachment....once you do it you'll never try any other method.

[Steve D.]

Re: 63_Distributor won't drop unless bumped

I saved the attachment, thanks. The problem is that manually I cannot get the distributor to drop in any position. I can rotate the rotor in small increments through 360 degrees and the dist will not drop in any of the positions.

[Larry M.]

Re: 63_Distributor won't drop unless bumped

By some chance, has a small piece of debris fallen down the manifold hole and lodged in the mating groove of the oil pump drive shaft, preventing the tang on the distributor gear from engaging?

Larry

[Steve D.]

Re: 63_Distributor won't drop unless bumped

I don't think so, because it drops in fine when the starter is bumped; I just can't get it to drop when I am manually positioning it.

[Duke W.]

Re: 63_Distributor won't drop unless bumped

1. Set the balancer notch to the normal initial timing point on the tab on the #1 compression stroke. Since you've been bumping the starter you will need to remove the #1 plug and feel for compression while you rotate the crank with the balancer center bolt

2. Place dist. above hole with the rotor pointing about 20 deg. CW from engine centerline.

3. Rotate bottom of dist. 90 deg. forward and note angular orientation of shaft flat.

4. Check that the oil pump intermediate drive shaft slot is oriented so the dist. shaft will slip in to the slot as the gears engage, which will rotate dist. shaft about 20 deg. CW as they do. A paint mixing stick can be used to "tweak" the oil pump intermediate drive shaft if necessary.

5. Start dist. installation with the rotor pointing along engine centerline. It will rotate about 20 deg. CW as the gears engage, and if you properly oriented the oil pump intermediate drive shaft, it should seat. If not, tweak the oil pump intermediate drive shaft as required.

6. Once the dist. seats rotate the housing until the points just begin to open. At this point the cap window should be near perpendicular to engine centerline, and the initial timing should be within a degree or two of where you set the balancer notch on the timing tab.

6. Snug down the dist. hold down bolt, but only enough that you can still turn the dist. by hand.

7. Start engine and set timing.

As long as the dist. is out you should verify that the dimple in the drive gear is oriented in the same direction as the rotor tip.

Duke

[Steve D.]

Re: 63_Distributor won't drop unless bumped

Update _ I pulled the intake manifold, and with the manifold off I set the distributor in and walked it around but still could not get it to drop without bumping the starter. So whatever is going on, this should eliminate misalignment of the intake manifold as a possible cause. I will try to make a short video clip of my installation efforts and post it.

[Mark E.]

Re: 63_Distributor won't drop unless bumped

"Bumping" and "aligning" the oil drive gear aren't necessary. It is quite easy to "walk the distributor" parts into position as Lars describes in this article. Too darn easy and the only way I do it. Steps 4 and 5 in the attachment....once you do it you'll never try any other method.

Thanks for the article. I didn't know about the walking technique.

The only thing I would add to Lars' article is that the #1 plug wire is not always on the same distributor terminal. On most models #1 is specified to be the terminal over the window; but on some it's one terminal clockwise from that. Check the AIM or FSM to verify.

[Stuart F.]

Re: 63_Distributor won't drop unless bumped

I discovered the walking technique by myself over 50 years ago and have used it ever since and described it to probably a hundred Chevy V8 owners over the years. I have found that lately in my old age I've lost a little of my touch or feel for doing it and I sometimes have difficulty.

Stu Fox

[Mark E.]

Re: 63_Distributor won't drop unless bumped

Why would bumping the starter enable the distributed to drop, when other methods failed? Maybe the dist to oil pump shaft connection is hanging a bit, and the shock of the starter bump overcomes that?