Distributor Shaft

[Jeff Y.]

I am rebuilding my distributor and need to replace the shaft, the tach gear is shot. Having trouble figuring out which one to get and from who. I have a '72 454 4-speed. Could someone help point me to a vendor and a part number? Same question for the Vacuum Advance.

Thanks,

Jeff

[John M.]

Re: Distributor Shaft

Jeff, Scroll down to Joe Ciarravino's Post on "Distributor Main Shaft Photo."
It may not make you happy but it's informative.
John

[Joe L.]

Re: Distributor Shaft

I am rebuilding my distributor and need to replace the shaft, the tach gear is shot. Having trouble figuring out which one to get and from who. I have a '72 454 4-speed. Could someone help point me to a vendor and a part number? Same question for the Vacuum Advance.

Thanks,

Jeff

Jeff------


None of the replacements have an auto cam that is configured like your original. So, your best bet if you want to retain the original centrifugal advance characteristics is to purchase a new shaft and transfer the auto cam from the old shaft to the new. This requires brazing. If you are not comfortable doing that a distributor specialist like Dave Fiedler at TI Specialties can do it for you.

[Jeff Y.]

Re: Distributor Shaft

Thanks John. I did purchase a new shaft and the cam is on upside down and does not match my original.
Joe - I like your approach. I'll contact Dave.

[Jim T.]

Re: Distributor Shaft

Joe do you know if there is a special position for the old auto cam to be reinstalled on a new distributor shaft?

[Joe L.]

Re: Distributor Shaft

Joe do you know if there is a special position for the old auto cam to be reinstalled on a new distributor shaft?

Jim------

I don't think it's critical, but I'd install it so that it is in the same position as original relative to the drive gear pin hole and blade on the bottom of the shaft.

[William C.]

Re: Distributor Shaft

Joe is correct with respect to the orientation of the autocam to the drive gear pin hole. If off position, you will have difficulty getting the correct initial advance without the vacuum can hitting one solid object or another. The easy fix if you have this issue is to pull the distributor and pull the pin from the bottom gear, rotate it 180 degrees, reinstall, and you should be back in business. Odd number of teeth on the distributor gear makes this adjustabilty feasible.

[Jeff Y.]

Re: Distributor Shaft

So before I spend money to get my cam brazed on a new shaft I have to ask if it is really worth it for something that will never be seen. Is the performance I'll get out of a repro shaft going to be that different from the original? I'm leaning toward get the cam brazed on the new shaft but had to ask.

Thanks,

Jeff

[Joe L.]

Re: Distributor Shaft

So before I spend money to get my cam brazed on a new shaft I have to ask if it is really worth it for something that will never be seen. Is the performance I'll get out of a repro shaft going to be that different from the original? I'm leaning toward get the cam brazed on the new shaft but had to ask.

Thanks,

Jeff

Jeff------


This has absolutely nothing to do with originality for "judging" purposes. I'd never recommend that one go to the effort of maintaining original configuration for a part that can't be seen or judged. However, in this case it's all about maintaining the original auto cam for the purpose of maintaining the original centrifugal advance characteristics. When one goes "messing around" with advance characteristics in a stock engine, one often ends up with disappointment and problems. The "reproduction" shafts with more-or-less generic auto cams can have this effect. There are 2 ways of keeping a distributor's performance characteristics the same as original:

1) Build the distributor with all of the internal components, including the shaft/autocam, as specified in the original blueprints for the distributor. This involves obtaining components that are long-since GM-discontinued;

2) Have someone with experience and a Sun distributor machine set up the distributor to the original specifications.

[Jeff Y.]

Re: Distributor Shaft

Thanks Joe, I didn't mean to imply your comments were cosmetic or for judging only, sorry if I came across like that. You answered my question as I expected. I really knew the answer just needed to hear it I guess. The cost is going to be quite a bit more to transfer the cam, just wanted to know what I could expect from a replacement before I spent the $ to restore the original.

Thanks,

Jeff

[Joe C.]

Re: Distributor Shaft

Jeff,

The clocking of the autocam relative to the roll pin or oil pump drive blade has no bearing on timing, distributor clocking, or engine operation, whatsoever.

[William C.]

Re: Distributor Shaft

Well I'd take a slight issue with the clocking comment as the relation of the autocam (that actually drives the distributor points lobes) is required to be in a specific location to allow the timing to be adjusted within the available "swing" of rotation between the vacuum advance and the manifold. Fortunately, if interference is encountered, all that is required is to take the pin out of the lower gear, and rotate the gear 180 degress and reinstall the pin. The "factory" setting is to have the dimple on the lower gear aligned with the tip of the dist rotor. If that is not allowing proper initial timing after the repair, the fix is to pull the distributor and rotate the lower gear so the dimple points away from the rotor. Just something to be aware of if you are going to replace the autocam on a new shaft.

[John D.]

Re: Distributor Shaft

Where are all these bad distributor shaft coming from guys. The ones with the football welded upside down.

[Jeff Y.]

Re: Distributor Shaft

John, Mine came from ZIP, they were really good about taking it back. They also told me they had no more in stock, might be a good thing, maybe no one else will get one upside down.

I'm still wondering if someone has used one of the reproduction shafts in a LS5 and can tell me how it performed?

[William C.]

Re: Distributor Shaft

One of the good ideas with ANY of the reproduction shafts is have the finished assembly tested on a distributor machine and adjusted as close to the original (or your idea of what you want) as possible.