63 Tach Drive Distributor - Part 2

[Timothy B.]

Re: 63 Tach Drive Distributor - Part 2

Stu,

Do a google search for something like "corvette distributor cross shaft repair button" and hopefully a picture will pop up and you will get the idea.

I forgot to add that the button has a approx. 1/2" head so to get it to sit flush the distributor needs to be milled about 1/16" deep at approx 1/2"-5/8" diameter so the button sits flush with the inside housing. You can also modify the button to make the head smaller and get a smaller mill that will fit a hand drill. The button head only has to make contact with the cross shaft gear.

[Joe L.]

Re: 63 Tach Drive Distributor - Part 2

Stu,

Do a google search for something like "corvette distributor cross shaft repair button" and hopefully a picture will pop up and you will get the idea.

I forgot to add that the button has a approx. 1/2" head so to get it to sit flush the distributor needs to be milled about 1/16" deep at approx 1/2"-5/8" diameter so the button sits flush with the inside housing. You can also modify the button to make the head smaller and get a smaller mill that will fit a hand drill. The button head only has to make contact with the cross shaft gear.

Timothy------


I used to think that milling of the cavity was necessary to allow for the thickness of the button. However, I no longer think so. I measured the depth of the cavity for a GM distributor housing originally manufactured without provisions for the button and one manufactured with provisions for the button. They were the same as close as I could measure them. The GM nylon button is about the same thickness as the brass button.

The original distributor in my original owner 1969 lasted about 35,000 miles before the tach drive gears stripped due to wear by the cross gear into the housing. The replacement GM distributor I bought had the nylon button. It lasted about 165,000 miles and was still going strong when I took it out of service. The nylon button is still there and there is NO wear on the housing, at all.

[Timothy B.]

Re: 63 Tach Drive Distributor - Part 2

Joe,

Using the nylon button is probably the best repair for these older style distributors. Do you know if this button is available in aftermarket or GM?

My experience is that the fit is tight when the button is not flush with the housing and the washer needs to be removed. The washer only protects the large screw in bushing from the cross gear teeth.

[Joe L.]

Re: 63 Tach Drive Distributor - Part 2

Joe,

Using the nylon button is probably the best repair for these older style distributors. Do you know if this button is available in aftermarket or GM?

My experience is that the fit is tight when the button is not flush with the housing and the washer needs to be removed. The washer only protects the large screw in bushing from the cross gear teeth.

Timothy-----

The GM #1957329 button was discontinued without supercession in June, 1993. I do not know of any aftermarket replacements, but there may be one.

[Donald L.]

Re: 63 Tach Drive Distributor - Part 2

Joe,

Using the nylon button is probably the best repair for these older style distributors. Do you know if this button is available in aftermarket or GM?

My experience is that the fit is tight when the button is not flush with the housing and the washer needs to be removed. The washer only protects the large screw in bushing from the cross gear teeth.

Long Island Corvette lists a "plastic Thrust Button" on their catalog.

http://www.licorvette.com/pdfcatalogfiles/cat/48.pdf

[Stuart F.]

Re: 63 Tach Drive Distributor - Part 2

Donald;

Yes, another option. I wonder if Long Island Corvette has a minimum order. I'll check my downloaded catalog or call them tomorrow. Thanks.

Joe; Your 69 story makes me certain that this effort is worth it. I have a spare Non-tach drive distributor on the shelf, but I'd rather not have to use it due to a failure of my original.

Tim; Thanks for your insight.

Stu Fox

[Stuart F.]

Re: 63 Tach Drive Distributor - Part 2

Just as a few follow on questions, or maybe part 3;

I decided my main shaft had too many scratch marks at the bottom bushing position, perhaps caused by the wear in the tach drive part of the housing (?). Regardless, I'm going to change the shaft and both bushings. I've ordered the Bronze bushings from Eckler's that are more expensive and question my ability to remove the old ones, and specially press/pound in the new ones w/o damage - any thoughts?

Also, I use a Dyna-Flyte ball bearing plate which I clean and re-oil from the top. It does not get any lubrication from the distributor, perse. I question whether I still need the grease well re-packed and the felt washer oiled?? Is the purpose of these to lube the standard distributor advance plate only, or do they supplement the engine oil system for lubricating the top shaft bushing? Your thoughts please.

Stu Fox

[Joe L.]

Re: 63 Tach Drive Distributor - Part 2

Just as a few follow on questions, or maybe part 3;

I decided my main shaft had too many scratch marks at the bottom bushing position, perhaps caused by the wear in the tach drive part of the housing (?). Regardless, I'm going to change the shaft and both bushings. I've ordered the Bronze bushings from Eckler's that are more expensive and question my ability to remove the old ones, and specially press/pound in the new ones w/o damage - any thoughts?

Also, I use a Dyna-Flyte ball bearing plate which I clean and re-oil from the top. It does not get any lubrication from the distributor, perse. I question whether I still need the grease well re-packed and the felt washer oiled?? Is the purpose of these to lube the standard distributor advance plate only, or do they supplement the engine oil system for lubricating the top shaft bushing? Your thoughts please.

Stu Fox

Stu------

I recommend having the bushings installed by someone experienced with this operation. The original bushings were line-bored to achieve proper alignment. I recommend having the same thing done now.

I'm not familiar with the "Dyna-Flyte ball bearing plate". However, the purpose of the grease well in the upper distributor housing is to provide lubrication for the upper distributor housing bushing. The engine's oil system provides little, if any, lubrication for the upper bushing.

[Stuart F.]

Re: 63 Tach Drive Distributor - Part 2

Joe;

Thanks for your response. I'm inclined to agree about having the bushings pressed in. The vendors make it sound simple in their instructions, but I don't really know what i am dealing with regards to exact sizes, tolerances and clearances. Mr. Fiedler in his Restoration Article specifically says to use Bearing Bronze, not Oilite, brass or silicone bronze bushings, but doesn't say why. Most of the vendors only handle the ones advises against.

My question about the upper lubrication needs are better understood now that I have cleaned up the housing and noticed there is a small hole in the upper bushing that lines up with the grease well. What fooled me was that the bushing is installed so that 1-3/16" sticks up above the bottom of the well and the outside of it becomes the bearing surface for the standard advance plate. When I install my B. B. plate, I use loctite on that bearing surface to secure the inner part of the plate. The outer part rotates on a 1-7/8" diameter ball bearing ring. It's a nicely designed product with virtually no need for it in the market. I have had a few since the early 70's so I might as well use them. Trouble is, as I now know, they will easily outlast the rest of the distributor. I cut my teeth on early model distributors that were prone to having advance plates that wore the inner bushings and tended to tip.

Stu Fox

[Joe L.]

Re: 63 Tach Drive Distributor - Part 2

Joe;

Thanks for your response. I'm inclined to agree about having the bushings pressed in. The vendors make it sound simple in their instructions, but I don't really know what i am dealing with regards to exact sizes, tolerances and clearances. Mr. Fiedler in his Restoration Article specifically says to use Bearing Bronze, not Oilite, brass or silicone bronze bushings, but doesn't say why. Most of the vendors only handle the ones advises against.

My question about the upper lubrication needs are better understood now that I have cleaned up the housing and noticed there is a small hole in the upper bushing that lines up with the grease well. What fooled me was that the bushing is installed so that 1-3/16" sticks up above the bottom of the well and the outside of it becomes the bearing surface for the standard advance plate. When I install my B. B. plate, I use loctite on that bearing surface to secure the inner part of the plate. The outer part rotates on a 1-7/8" diameter ball bearing ring. It's a nicely designed product with virtually no need for it in the market. I have had a few since the early 70's so I might as well use them. Trouble is, as I now know, they will easily outlast the rest of the distributor. I cut my teeth on early model distributors that were prone to having advance plates that wore the inner bushings and tended to tip.

Stu Fox

Stu------

One thing to keep in mind: GM never sold the bushings, upper or lower, for 62+ distributors. The only way you got the bushings from GM was as part of a complete housing assembly. I'm pretty sure that GM did it this way because they did not consider the bushings to be "field serviceable". Of course, with the housings long-since GM-discontinued, a few have "stepped up to the plate" and developed the procedures and tooling to install the bushings the way Delco-Remy did.

[Charles M.]

Re: 63 Tach Drive Distributor - Part 2

Can anyone post some pics of these parts, not to familiar with this part or repair.
Thanks
Chalie

[Stuart F.]

Re: 63 Tach Drive Distributor - Part 2

The best source for good pictures of the bushings and tool kits is an on line catalog from Eckler's or Corvette Central. Just check Distributor or Ignition parts for C-2 or C-3 Corvettes.

Not that anyone is interested, but I will be taking pictures of my Ball Bearing vacuum advance plate before I re-install it, as well as other pertinent items and procedures I take in my distributor rehab project.

Sure wish I could get more respondents from those who have done this as well.

Stu Fox

[Duke W.]

Re: 63 Tach Drive Distributor - Part 2

If the shaft is snug in the housing bushings, then the bushings don't need to be replaced. Detectable side play should be nil to barely perceptible. Mic the mainshaft to see if it is worn. Any scratches can be polished out with some 600 paper wetted with mineral spirits.

Look up the thread I stated two years ago on overhauling an original 90K mile L-79 distributor.

Duke

[Stuart F.]

Re: 63 Tach Drive Distributor - Part 2

Duke;

Thanks for your response. I will try to locate your thread on the L-79 Distributor.

Basically, my shaft fits well in the housing with no detectable side play. My concern is for a section of about 1/2" long at the top part of the lower bushing area. There are several grooves that are perceptible to the naked eye in profile, and a few small ridges - none of which can be miced obviously. The shaft to either side of the area mics close to standard .489", with a little varnish above and polish wear below.

Stu Fox

[Steve G.]

Re: 63 Tach Drive Distributor - Part 2

Duke;

Thanks for your response. I will try to locate your thread on the L-79 Distributor.

Basically, my shaft fits well in the housing with no detectable side play. My concern is for a section of about 1/2" long at the top part of the lower bushing area. There are several grooves that are perceptible to the naked eye in profile, and a few small ridges - none of which can be miced obviously. The shaft to either side of the area mics close to standard .489", with a little varnish above and polish wear below.

Stu Fox

Just to provide a second opinion, if you have no measurable side play, leave the bushings alone. The chances of achieving that without a reamer of appropriate size or line honing are very low. And if the replacement bushings that you buy are already finished to size they can't be line honed.

It's not just about the id of the bushing. The id's have to be in perfect alignment with one another as well as perfect diameter. That's why in production an undersize bushing was pushed in and the bore size of both bushings finished together in one operation for perfect alignment and size.