ID this distributor shaft

[Gerald L.]

Still contemplating my 63-340 distributor. Unit was rehabbed in the 80s o/a the usual tech gear shredding, i. e. new shaft. Any idea of the meaning of the stamped underscored 54 at the end of the shaft football? Does not seem to be the last digits of a part number.

Incidentally the weights show 37 and the cam/weight plate 724CCW, no peg bushing, springs are huge and longish. From others on the forum these are correct for a 63 340. I have replaced the 201 VAC for a more 2" rule compliant B26 for my 15" idle vacuum (cam is unknown).

Ignore the rubber bands in the pix. I considered doing a timing check with the peg fixed at the slot beginning end but I elected not to. I feel certain that springs take a slight set at idle rpm and so the peg advances in the slot and adds to initial advance. You can actually nudge the weights with your finger and they, with the cam plate, will stay in place. I estimate this to be 6 to 8 distributor degrees. I do get a full 24 crank degrees mechanical advance above idle.

I elected to not test this as I was looking for distributor reasons why it is up against the manifold. Then I realized it was working for me.

Maybe it is true that replacement cams have poorly indexed distributor drive gear teeth, compared to original, and so they don;t set in the middle between the coil bracket and the manifold.

[John D.]

Re: ID this distributor shaft

Gerald, The 54 means you have the correct "football" at the end of the shaft. The correct shaft.
If you had a 54W that was sold over the counter that would be incorrect.
You have the correct 724 and the
correct #37 weights.
You are missing the peg bushing.
15" vacuum is decent. My '63 has 16" at 900 RPM. John

[Gerald L.]

Re: ID this distributor shaft

John, thank you for your reply. So everything in the distributor is like original, ex VAC and my new springs. So the distributor is not the reason it is jammed to the manifold. Since the timing tab does correctly mark TDC I guess I am in the camp that feels the cause lays with poor gear alignment in after market cams.

[John D.]

Re: ID this distributor shaft

Sounds like you may be one tooth off Gerald.

[Gerald L.]

Re: ID this distributor shaft

Sounds like you may be one tooth off Gerald.

John, I did pull distributor, the driven gear dimple did face the rotor, and I did rotate it 180 on the shaft. Result was the distributor then initial timed well but was hard against the coil bracket. It had been against the manifold for 30+ years, I was accustomed to it there, so I rotated the gear back to dimple being correct and back to the manifold it went. A half of a full tooth rotation is just greater than the gap available for the VAC between the coil bracket and the manifold, which is no more than about 7/8 inch.

The rest is a little geometry and just this person's thinking. Rotating the gear 180 on the shaft is a half tooth rotation and is about 14 distributor degrees, 360/(13X2)=14. A full tooth is twice that at 28 degrees, 360/13=28. The gap of 7/8" cited above is about 4 inches from the dist center line so this gap is about 13 distributor degrees, (0.875/(4x2x3.14159))/360=13. This is a math check for the real experience cited above, a half tooth is the entire gap available to set the distributor on this 340 engine.

This sort of puts me in the camp with those who think the issue is not in a rebuilt distributor (at least mine) but is with replacement cam gear indexing during the cam grind. It only needs to be off +/- 6 or 7 degrees to push the distributor to the end of the gap on this engine, ie to the coil or the manifold. Considering how critical the indexing of the ramping of 16 cam lobes should be I find it hard to accept such slop for the gear. But then again it would not be noticeable on engines with more room for the distributor.

[John D.]

Re: ID this distributor shaft

Gerald, Don Baker is our guru on distributors. He taught me a lot.
I mostly talk with fuel injection owners. Here's something I tell them. If you remove the distributor clamp and lift the distributor up in the air a few inches and put it back down in the hole you are one tooth off.
Don and I have so much trouble with the above. John

[Roger W.]

Re: ID this distributor shaft

John,
Can you refresh my memory? What is so special about this distributor shaft?

Thanks