Tach Drive Distributor Bushings

[Joe L.]

Re: Tach Drive Distributor Bushings

OK, here's the problem with the bushings that are currently available from ANY Corvette Warehouse! When the bushing is driven into the distributor housing the ID of the bushing is decreased and makes the bushing either tight or too tight.
The perfect bushing is a bronze-silicone-aluminum bushing or oilite with teflon. Either can be obtained from ANY distributor that specializes in bearings. Specify the correct OD and make sure the inside (ID) is either the same or smaller than the stock bushing.
NOW the problem is making the ID correct and this cannot be done with a DRILL BIT! You will have to borrow or obtain a set of reemers with the correct ID size.
OR you can have a lathe like Gary R. suggests and turn (reem) the ID to the correct size.
What I am really saying is that this is not a job that the shade tree mechanic can accomplish without the correct equipment.
Bite the bullet boys and PAY someone to do a professional job.

JR

JR------


Yes, and this is why I've always figured that GM never offered the bushings in SERVICE for 1962 and later distributors---they did not consider the bushings to be "field serviceable". If one needed the bushings, then one could best do it by replacing the complete housing which included factory-installed bushings.

Of course, the housings are long-since discontinued so now methods for proper field service of the bushings are necessary.

[Gary R.]

Re: Tach Drive Distributor Bushings

To add to the soup on distributors, when I did mine I couldn't find a quality main shaft or especially a cross gear. I did what everone does, go through a couple of vendors and got the same part from them all. All of them were no good. The gears were not machined correctly, which caused them to bind-by hand. I was told to fit them to get the correct lash on them, this sounded like total BS to me since most guys aren't going to have a lathe or mill to fit them. Since I do I took them up on it and faced the brass button on the gear head end that was on all the new cross gears. I faced them in 001-002" increments and attempted to get a mesh that would work. I couldn't. I then removed the brass button, installed a longer one and started over. Still no good. I ended up finding a good used GM cross gear in my box of vette junk and it worked perfect. I also went to the bearing cross gear of the time, that was better much still no where as good as the GM gear was.

The main shafts I bought were a mix of good and bad. I ended up returning all of them and making up what I needed from older parts I found.

Maybe this has changed since them, that was about 7-10 years ago. The distributor I built is in the car and I have no problem with it, the others are sitting in boxes somewhere in my shop!

[Stuart F.]

Re: Tach Drive Distributor Bushings

Boy! This is a scary topic. I have about 44k miles on mine and had it apart twice - last to shim the shaft end play for my Pertronix conversion (10k ago), and previously to change the advance plate to a ball bearing unit. Each time I checked the shaft side play and it seemed fine. How much longer can I expect it will give me good service?? (I'm 72 yrs old, which will go first?).

Stu Fox

[Dick W.]

Re: Tach Drive Distributor Bushings

If you want a round ID, ream it. A drill bit will wobble. I rebuilt distributors for years (not now though) and bought a sized reamer (not for sale) just for that job. Here is what I bought

[Joe L.]

Re: Tach Drive Distributor Bushings

If you want a round ID, ream it. A drill bit will wobble. I rebuilt distributors for years (not now though) and bought a sized reamer (not for sale) just for that job. Here is what I bought

Dick------


Are you talking about one of the adjustable size, hand reamers?

[Dick W.]

Re: Tach Drive Distributor Bushings

Dick------


Are you talking about one of the adjustable size, hand reamers?

Yes Joe, you just have to take your time with a hand reamer, use plenty of lubricant ( I use mineral spirits) and measure often with a either an appropiately sized small hole gage or snap gage, ever which one you have access to. I use both, depending on which one I get to first, and have found no measurable difference with either

[Clem Z.]

Re: Tach Drive Distributor Bushings

the best type of expansion reamer to use is the one used for bushed electric motors as they have a extension that goes thru both bushing so everything is in lined when reaming the bushing

[Dick W.]

Re: Tach Drive Distributor Bushings

the best type of expansion reamer to use is the one used for bushed electric motors as they have a extension that goes thru both bushing so everything is in lined when reaming the bushing

That is what I have Clemster

[Mike Z.]

Re: Tach Drive Distributor Bushings

Clem & Dick-
So, what is the part number and/or source of the reamer for "bushed electric motors"-I went all through the link Dick posted McMaster-Carr. All they had was a 3" ream and total of 6" in length-at least that is what I saw.
I do a ton of distributor rebuilds in my shop. I made a hone that uses emery cloth-works great, but I can see the value in a ream that sizes both ends straight. I think part of the key is a straight installation, which I made another tool to install the new bushing out of an old mainshaft and lower gear, which aligns the new bushing with the other end-works great, especially if you don't have to change both out: 98% of the time it is only the lower.
I agree with several other comments that the extra drill hole is not necessary, as there is an oiling hole in the lower housing-later housings have two holes. The bushings are readily available from most all the "big box" suppliers, as are the mainshafts.
Word to the wise: if there is any detectable movement laterally in the shaft, more than a few thousands-almost certain the bushing is gone. If you catch a finger/thumb nail on any grooves on the shaft-it is toast also=both need to be changed out.
Thanks,
Mike Zamora
#12455

[Dick W.]

Re: Tach Drive Distributor Bushings

Mike, I have not a clue as to where I purchased mine. I probably have had it for 35-40 years. I would think that a good machine tool supply would have one.

[Clem Z.]

Re: Tach Drive Distributor Bushings

Clem & Dick-
So, what is the part number and/or source of the reamer for "bushed electric motors"-I went all through the link Dick posted McMaster-Carr. All they had was a 3" ream and total of 6" in length-at least that is what I saw.
I do a ton of distributor rebuilds in my shop. I made a hone that uses emery cloth-works great, but I can see the value in a ream that sizes both ends straight. I think part of the key is a straight installation, which I made another tool to install the new bushing out of an old mainshaft and lower gear, which aligns the new bushing with the other end-works great, especially if you don't have to change both out: 98% of the time it is only the lower.
I agree with several other comments that the extra drill hole is not necessary, as there is an oiling hole in the lower housing-later housings have two holes. The bushings are readily available from most all the "big box" suppliers, as are the mainshafts.
Word to the wise: if there is any detectable movement laterally in the shaft, more than a few thousands-almost certain the bushing is gone. If you catch a finger/thumb nail on any grooves on the shaft-it is toast also=both need to be changed out.
Thanks,
Mike Zamora
#12455

if you have a electric motor repair shop near you check with them. i think they were made by blue point. reaming electric motors may be a lost art these days as the cost of bushing motors is so low it most likely does not pay to rebuild them. if you have access to a machine shop you can have them take a regular expanding reamer and add a extension to it. the standard way of oiling the bushing is the oil runs into the bottom hole above the bushing but if the bushing is a tight fit it will not get much oil and that is why i suggest full pressure oiling or spiral groove the shaft so the oil get into the bushing. i always used moly kote(camshaft breakin compound) on on the shafts so they would not dry start on a rebuild. when i retired 17 years ago i sold a lot of the small tooling i had.

[Gary R.]

Re: Tach Drive Distributor Bushings

Just a note to those who may machine oilite. In most cases you do not want to machine it smooth. I have with some applications such as a steering bushing because the shaft never spins fast and never 360*.

Oilite is oil impregnated for those that may not know, the surface is very porus to allow the oil to flow when heated to lube the bushing and shaft. It works very well for the intended purpose. However when you machine the ID of a oilite bushing and make it smooth the pores are then machined "closed" and in effect looses the properties it was designed for. I would cut in some oil grooves if you go in that direction, same as if you use 660 bronze. Unlike a steering pitman shaft, the distributor main shaft spins just a little faster so you want to have the engine oil getting to it.

Several years ago I had a long discussion about this the VP of Beemer Precision, the makers of oilite. You can look them up on the web as well.

[Joe C.]

Re: Tach Drive Distributor Bushings

Just a note to those who may machine oilite. In most cases you do not what to machine it smooth. I have with some applications such as a steering bushing because the shaft never spins fast and never 360*.

Oilite is oil impregnated for those that may not know, the surface is very porus to allow the oil to flow when heated to lube the bushing and shaft. It works very well for the intended purpose. However when you machine the ID of a oilite bushing and make it smooth the pores are then machined "closed" and in effect looses the properties it was designed for. I would cut in some oil grooves if you go in that direction, same as if you use 660 bronze. Unlike a steering pitman shaft, the distributor main shaft spins just a little faster so you want to have the engine oil getting to it.

Several years ago I had a long discussion about this the VP of Beemer Precision, the makers of oilite. You can look them up on the web as well.

It now appears that the better choice for the lower bushing is bronze, not oilite.

In order to mitigate any potential problems resulting from a non concentric lower bushing, I will take Clem's advice and use pressure oiling. It makes sense that this approach will emulate the functioning of main/rod bearings in that the pressurized oil will ensure a constant film which will prevent metal-to-metal contact.

[Joe R.]

Re: Tach Drive Distributor Bushings

It now appears that the better choice for the lower bushing is bronze, not oilite.

In order to mitigate any potential problems resulting from a non concentric lower bushing, I will take Clem's advice and use pressure oiling. It makes sense that this approach will emulate the functioning of main/rod bearings in that the pressurized oil will ensure a constant film which will prevent metal-to-metal contact.

Hey Joe,

Pressurized oil is a good idea for the lower bearing. What about the upper bearing? It turns at the same rpm as the lower bearing. How is pressurized oil getting to the upper bearing when there is a hole in the housing the size of a dime (large anyway) ?

You think maybe oiling the wick at the top in the housing will keep it lubed for maybe say 100,000 miles or more?

JR

JR

[Clem Z.]

Re: Tach Drive Distributor Bushings

Hey Joe,

Pressurized oil is a good idea for the lower bearing. What about the upper bearing? It turns at the same rpm as the lower bearing. How is pressurized oil getting to the upper bearing when there is a hole in the housing the size of a dime (large anyway) ?

You think maybe oiling the wick at the top in the housing will keep it lubed for maybe say 100,000 miles or more?

JR

JR

i have never seen a top bushing wear as the only side thrust on it is from the points and if the dist is a TI there is no side thrust. the bottom bushing see a lot more side load from the oil pump