Distributor Bushings - jig-boring
I have been reading some past posts regarding bushing replacement in distributors and see a reference to "jig-boring" the replacement bushings. Forty years ago I don't remember this as an issue but I understand the reason you would want to do it now. I also understand that it has been 20-30+ years since distributors were made so there is not a big market for this service. My reading and curiosity have raised several questions. Was this "jig-boring" tool supplied by Kent-Moore Tools? Was there a tool number? If Kent-Moore was not involved, where did the jig tool come from? Does anyone have pictures? How much gap should there be between the distributor shaft and bushing for a correct fit? In the age of computers and CNC machine tools I would think this could be done easily but maybe not cheap. The distributors in question are 1110914 & 1110905. Because this topic is new to me I would appreciate any and all education received. Thank you.
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Re: Distributor Bushings - jig-boring
Terry;
I am not sure what the reason for the question? Attempting to fact check old information or improve a stock distributor. I looked up the numbers given and it looks like you are working on a 57 FI distributor. I will give it a shot.
The jig borer is a machine that was developed primarily to fill a need for precisely locating holes in jigs and dies.
If you are referring to Jig boring the distributor bushings for a extreme close tolerance distributor I am not sure you would get much for your effort. Even finding a jig borer these days may be difficult. One could build custom bushings, on a lathe, and have them line honed and get close to the same tolerances you might expect with a jib borer for less money. Playing close attention to the end clearance(play) would likely do more for spark accuracy than any improvement over factory tolerances. Also eliminating the inaccuracy of a set of points with a points eliminator may also help, but ist's my guess this isn't what you want. Or are you having issues with the fuel pump drive?
Rick -
Re: Distributor Bushings - jig-boring
Rick------
In the case of distributors, jig boring refers to a machining process and equipment that results in the upper and lower bushings being precisely "in line". This is how the distributors were originally manufactured. As I recall, many, many years ago GM discontinued the bushings and SERVICED the bushings only as a complete assembly with the housing. Of course, this was an expensive way to replace. the bushings but I expect that GM found that field installation of the bushings was just not "getting the job done right" due to lack of the proper equipment and expertise.
Addendum:
By the way, there used to be a company in Florida that was set up to do jig boring of distributors. It was called High Tech Innovations and was run by a guy named Jim Dwyer. They did two distributor housing bushing installations for me and they both came out PERFECT. Unfortunately, Jim "cashed in his chips" many years ago and, after his passing, the company ceased to exist. Since that time, I don't know if anyone does this type work. Possibly, TI Specialties does, though.Last edited by Joe L.; July 29, 2018, 10:56 AM.In Appreciation of John HinckleyComment
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Re: Distributor Bushings - jig-boring
Richard - Joe
Thank you for for your replies and information. My reason for my post was to get an education on a topic I know nothing about - "jig-boring". Many years ago, if a distributor needed rebuilding, I would drive out the worn bushings and drive in some new ones. Then if a new shaft would slide in, spin and feel tighter then the old parts, I would call it good. I also understood if something went wrong i could go to Chevrolet and buy a new part.
In reading past posts I was given the impression that "jig-boring" was the recommended thing to do to correctly rebuild an older distributor. I assumed the reason to "jig-bore" was to precisely align the holes in the bushings avoiding undue wear on the shaft and bushings. Not knowing what information may be needed, I used the numbers of two distributors I had on the shelf as repair examples.
I am a little thick headed but what I am hearing from you is that "jig-boring" is needed if someone is looking for perfection in a distributor rebuild. But if someone is looking for the performance required for a nice Saturday night drive, reaming or line honing of the bushings would be the recommended way to go. Is my understanding correct? I appreciate the education you are providing. Thank you.Comment
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Re: Distributor Bushings - jig-boring
Terry------
Yes, I'd say you are correct. The vast majority of distributor bushings have probably been replaced just as you mentioned and the so-repaired distributors went on to provide perfectly satisfactory service. I would say that jig boring is a preferred method but certainly not necessaryIn Appreciation of John HinckleyComment
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Re: Distributor Bushings - jig-boring
Moore Jig Bore, Bridgeport CT. Also make Jig Grinders. We had one in trade school- pre CNC days, the teacher never taught us how to use it and locked it up in caged stockroom. I think I recall seeing just one kid use it during my 4 years there.
I agree, I have rebuild distributor and didn't use a Jig Bore, never had a problem.Comment
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Re: Distributor Bushings - jig-boring
Joe,
We're the original bushings oilite bronze like a crankshaft pilot bushing? I would think a machine shop could make bushings the same height and OD as the originals then reem the complete assembly for a straight snug fit.Comment
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Re: Distributor Bushings - jig-boring
A big THANK YOU to everyone who offered information. I've learned a lot and for me that is a big and satisfying part of this hobby.Comment
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