Tach Drive Gears gone.

[Rich W.]

Re: Tach Drive Gears gone.

I looked at that a good bit after I cleaned it up..its only a scratch type mark..not really all that bad..can feel it with my pocket screw driver..I got a new button to go on the gear..I may do the gear mesh check on it to see where it ends up..like a rear end set up! Might be fun to try.

[Rich W.]

Re: Tach Drive Gears gone.

Ok I figured out how to search in mobile..I have been trying different keywords for the brass button in the distributor for the tach drive gear that mine doesn't have to install one myself..the one that is a plastic in the 70 up stock housing..I took it to a machine shop and they want to use a bridgeport to drill it into the housing..costing $$$$ ..if anyone can point me in the right direction for self install I would appreciate the keyword help.

[William C.]

Re: Tach Drive Gears gone.

You don't really need a bridgeport, a standard drill press will do, or even a hand drill. The secret is to use a guide to center the drill in the hole. The tip of the brass bushing can be shortened to fit the depth of the hole (once assembled the tip will have only a little room to move so "falling out" is not an issue, so you leave enough meat in the housing that the drill doesn't go thru the back. The housing is cast iron and machines easily.

[Rich W.]

Re: Tach Drive Gears gone.

I think what I have run into is that I need to recess the brass bushing flush with the inside of the housing..drilling the small hole into the housing is easy..I could use the old tach gear holder as a guide ..perfect center..its the recess part that gets tricky..I need a .520 drill bit that has no point..a mill type drill bit is needed..and they cost more than what it will cost me to have them drill it for me..so that's what I was looking for..a bit or another way to drill it flat..just an FYI on what I am using..its from Corvette America part number x2557..

[William C.]

Re: Tach Drive Gears gone.

You are still making it too hard, there is enough clearance in the setup if you remove one of the small shims on the crossgear, and make the pilot pin hole deep enough to get the large brass surface flush against the existing machined surface of the housing you will be A-ok. Try it once before you go to extremes.

[Larry M.]

Re: Tach Drive Gears gone.

I think what I have run into is that I need to recess the brass bushing flush with the inside of the housing..drilling the small hole into the housing is easy..I could use the old tach gear holder as a guide ..perfect center..its the recess part that gets tricky..I need a .520 drill bit that has no point..a mill type drill bit is needed..and they cost more than what it will cost me to have them drill it for me..so that's what I was looking for..a bit or another way to drill it flat..just an FYI on what I am using..its from Corvette America part number x2557..

There are "kits" available to do this job. Centering bushing and special drill bit and instructions, etc. I think Paragon, CC, and Ecklers have them for sale. If you can't find them, let us know and I will do a search for you.

Larry

[Rich W.]

Re: Tach Drive Gears gone.

Well I know you're right..I think part of it is the new design of gear and coupler is machined to remove all but end play of the gear..its a brass piece with needle bearings in it..the gear itself only has one washer on it that seems to be so it doesn't chew up the coupler..the gear is machined longer where it rides on the brass piece I am trying to put in..makes me wish I had a 70! I understand what you mean..don't recess the new bushing..just drill the small hole and let it ride..it wont fall out and it can't go anywhere..makes sense..if I do that then I will have to machine or sand down the end of the new gear end where it rides on..I barely have movement now with the worn distributor when I test fit the new coupler and gear..so then is the answer right in front of me..don't screw the coupler all the way in..I guess that's the question I have now..will the gears..shaft and tach..mesh properly if I leave it out a few turns..I took it out by hand so the stripped one wasn't all that tight to begin with...

[Timothy B.]

Re: Tach Drive Gears gone.

Rich,

There is a post by me some time ago about this process, look in archives.

After you drill the pilot hole, I believe you need what's called a end mill to mill approx 1/16" depth so the new button will sit flush with the housing. By doing this you can keep the hardened washer as the factory installed to protect the brass bushing. You can also turn the new button in a drill and file down the OD so it fit in the end mill recess as it's plenty big in OD.

[William C.]

Re: Tach Drive Gears gone.

Frankly, never saw one of the large brass collars that hold the gear wear out. IMHO, the needle bearing setup is Gross Overkill.

[Rich W.]

Re: Tach Drive Gears gone.

Rich,

There is a post by me some time ago about this process, look in archives.

After you drill the pilot hole, I believe you need what's called a end mill to mill approx 1/16" depth so the new button will sit flush with the housing. By doing this you can keep the hardened washer as the factory installed to protect the brass bushing. You can also turn the new button in a drill and file down the OD so it fit in the end mill recess as it's plenty big in OD.

Tim that's what I was looking for..I figured it needed a mill to recess it..its really hard to explian what is going on with these parts unless you have it in your hand..I don't have a mill but that may be the way I need to go..I agree that the roller bearing setup is over kill...that's why I am doing it..just need to get over that hump to get it done..oh and Tim..you do realize that you have over 6k posts..kinda tough to narrow down the one I need to see..on another note Tim..I see you are in the Mason Dixon chapter..I have looked at your site and see you have a couple of things going on Sunday May 1st..I got an invite email a while ago when I joined the NCRS to look into your chapter here..I may just end up down there! Thanks for everyones input..it means alot!

[Dick W.]

Re: Tach Drive Gears gone.

Agree with Clup. I have rebuilt many of those distributors and have never seen the brass worn out. The thrust load forces the driven gear into the cast housing, causing the wear. You can use the button, or you can drill the housing all the way thru, tap it and then use a socket head set screw to adjust your end play. If you do that, locktite the threads of the screw, set your end play, then grind off the excess screw sticking out. A little dab of epoxy, a little paint, and the judges will never know 'nuttin'

[Rich W.]

Re: Tach Drive Gears gone.

Now nobody mentioned that yet..drill thru and set screw..

[Timothy B.]

Re: Tach Drive Gears gone.

Rich,

Bill and Dick are correct in that the brass bushing will not wear out the thrust is inward. I just like to keep everything as original so using the mill and keeping the hardened washer is the way I have done these.

If you drill the small hole and install the button without the end mill the hardened washer will need to be removed to allow everything to spin freely. The set screw is a good idea, I used one but it stuck out the back just a fraction and I didn't like it.

[Rich W.]

Re: Tach Drive Gears gone.



Ok..here use the finished product..at least the bushing..I am still waiting on the vacuum advance..not sure but I was told I got one of the last ones in stock..plan to get that tomorrow ..

[Rich W.]

Re: Tach Drive Gears gone.

Got the vacuum advance today..its gm box was labeled from 95..I had a GM DPSM check for me..I got the last one from GM..it comes in at 8 lbs and all in at 14lbs.. so I put it in and popped it in the car..set up the dwell and did a quick basic timing..car runs awsome..tach is smooth as glass..and a straight a shot out of the coupler with no bend..thanks for the input all