67 distributor rebuild

[Justin N.]

Dear Members,
I just received my small parts kit and other stuff from Corvette Central to complete my rebuild. I dropped in the bronze gear button and there doesn't seem to be enough room(threads)for the set screw. Bubba had slammed a bolt in there originally. Do I have it assembled correctly? First, the button went in, then the gear, then I slipped over the thrust washer, and finally the coupler.
Thanks mucho! Justin

[William C.]

Re: 67 distributor rebuild

If you are using the setup I think you are, the thrust washer between the coupler and gear must be removed for clearance. The replacement front "stop" is much thicker than the plastic one GM introduced in the 70's

[Brian Monticello]

Re: 67 distributor rebuild

Are you planning on using the button and set screw together somehow? I think they are seperate solutions. When I did this (button route) I had to remove the thrust washer and shave the button. The button started about .053 and ended up ~.036. It was shaved by rubbing it across sandpaper.

Brian

[Timothy B.]

Re: 67 distributor rebuild

Where does the "button" fit? I rebuilt my 67 SB 300HP dist. recently and I could not find anywhere for such a part. I had ordered a plastic button from LI Vette, but it apparently didn't fit my dist. I am assuming you are talking about in-between the tach drive gear and the dist. housing? There is a tiny hole in the end of the tach drive gear with nothing in it.

[Joe C.]

Re: 67 distributor rebuild

Tim:

The "thrust button" came into use after 1967...not sure when, but might have been 1969 or so. You must drill a hole thru the dist housing at the point that the cross shaft contacts the inside of the housing. There are 2 ways to do this:

1. Drill a hole completely thru the housing, then fill and paint.
2. If you're good, then drill a blind hole from the inside. This is the way to go.

BTW, you bought the "right" button. I had no trouble installing the nylon button into my 1965 dist. It seems that the bronze buttons are too thick, and have to be shaved.

Joe

[Justin N.]

Re: 67 distributor rebuild

Dear members,
Thank you for the advice. I think I'll sand off some of the button and leave out the thrust washer. Bubba left out the washer and the button and had some 1 inch bolt sticking out like Frankenstein's neck. I think I just need to get the gears to line correctly. Hey Tim, I also have a 300hp 67 with the (ms 355 15)vaccuum advance dist. I wish the picture would have shown up, but it's a nightmare to download the pictures to a site. Obviously I hadn't done something correctly. As you slide the gear into the housing, on the other side(180 degrees) is a threaded hole. I now look into the hole and see the top of the bronze button, which doesn't seem to have enough threads to hold a screw as Paragon's picture on page 19,vol.28, 2003 catalog.

Justin

[Timothy B.]

Re: 67 distributor rebuild

OK, I am throughly confused. Why do I need to install a button at all on a 67 that didn't have it in the first place?? What is the button's purpose? Which year used the plastic versus the bronze button? My car has the thrust washer and no button, and does have a slight amount of play in the gear, but everything seems to work fine. What is the driving factor that would convince a person to drill into their dist housing??? Seems radical to me, but I likely don't understand the rationale. The part from LI Vette was a large black button that looked somewhat like a push-pin. If there was a hole in the dist the pin part would have stuck out the side of the dist.

[Brian Monticello]

Re: 67 distributor rebuild

In this picture you can see the wear caused by the cross gear and the hole I drilled. YES.... I KNOW -- I WAS NOT ON CENTER

Go here for some more pictures

http://65corvette.nonethewiser.net/monthly_journals/winter03-04.htm

There are two main methods for curing this problem

1. Set screw: hole is drilled in housing and a set screw is inserted so that the cross gear rides on the set screw instead of the housing. This is a good method because you can adjust end play by rotating the set screw.

2. Bronze Button:hole is drilled a a bronze bushing is pressed into the hole and the cross gear pushes against this surface. This solution is good because it does not require dead-on accuracy but the useful life of the button is questionable. End play is not adjustable and needs to be set up initially by shaving the button.

Sounds like Justin had a set screw (or a bolt) at one time and is now going to use the button. The button requires very little force to push in and out. If the cross gear burrows too far into the housing, the cross gear teeth will eventually be sheared off/chipped and you'll need a new cross gear and
mainshaft.

There is a specified endplay (can't remember now) but as you rotate the main shaft in different directions, the cross gear will move in and out. Measure the difference and you have your endplay measurement.

Brian

[Joe L.]

Re: 67 distributor rebuild

Tim, et al-----

The "button" is designed to serve as a low-wear thrust surface for the tach drive gear. These buttons were first installed in Corvette distributors for PRODUCTION about 1970. Soon thereafter, they became part of the SERVICE distributor assemblies for most older-model distributors then still available from GM under original or replacement part numbers.

These buttons are very important for tach drive gear longevity. Without them, the cross gear will often gall the rear of the distributor housing cavity, move laterally, and create gear mis-alignment which will result in the destruction of BOTH gears.

ALL GM distributors with the buton used the nylon button. The brass button is an aftermarket item but it works very well.

In order to install the button (either type) in a distributor housing not originally so-equipped, the housing has to be drilled for a retaining hole for the button locating pin. With the nylon button, the pin may protrude to the outer surface of the housing unless it's trimmed.

With the brass button, in order to get proper fitment, the best thing to do is to spot face the inside of the rear of the housing. This should be done centered on the button hole, for a diameter slightly exceeding the OD of the button, and for a depth of about 1/2 the thickness of the button.

Drilling the housing for the button is NOT radical, at all. As I say, all housings from about 1970 onward were so-drilled and a nylon button installed. The operation can be done in the ways that Joe described so as not to be externally apparent.

[Howard Nardick]

Re: nylon button

Joe,

Are you saying the nylon button is still available from GM?? If so please send or post a part number. THANKS!! HN.

[Joe L.]

Re: nylon button

Howard----

No, the nylon button, GM #1957329, is long-since GM-discontinued. I think that it's available in the aftermarket/reproduction, though.

[Jack W.]

Re: 67 distributor rebuild

Hey Brian, your button hole is off-center!

not that it irks you or anything like that . . . .

[Terry M.]

Re: 67 distributor rebuild

We begin to see the hole in the distributor housing in 1970 Corvettes about serial number 12,000. About this same time the Radio Frequency Interference (RFI) shield appeared on standard (points type) distributors. The distributor shielding changed from the box style used from 1968 to 1970 to the one-piece bent style used from around this point to 1974(5?)- or whenever HEI came into production. The small blocks also no longer used the front two flash chrome spark plug ignition shields at about this same time in 1970 production. I believe there are more detailed serial numbers in the 1970-1972 TIM&JG.

[Joe C.]

Re: nylon button

Howard:

See Tim Bond's post, above. He says he got his from LI Corvette Supply. I probably got mine from them also, as I buy the bulk of my parts from them.

Joe