This 72 is driving me nuts with it's "little" problems, here is my latest. The tach was not connected when I got the car (cable removed from distributor) so I just thought it was the "normal" bad side gear & shaft. Over the weekend I installed a new main shaft & side gear (both from the same vendor) after cleaning all the old junk out, and found that if I tightened the coupler all the way, it jammed the shaft was very hard to turn, if at all. If I loosened the coupler just a bit, it spun clockwise without issue, but made a sound that did not seem normal for a "gear to gear" drive. I also had purchased a 90 degree adapter so the tach cable would not be crimped with the tight spacing at the back of the engine, and found the "removable shaft" that comes with it, would not go into the side gear like the O.E. tach cable would. So I took the whole thing apart and installed the main shaft, side gear & coupler into another housing that I have. After doing this, the same problem was encountered with the coupler tightened down causing the shaft & gear to be jammed and it made the same noise when loosened (could this be just gear to gear noise, with slight stiffness?). I then looked back into catalogs & spoke to people at the vendor site, to see if there was a washer or spacer that was missed and should be behind the coupler (both distributor housings have brand new GM driven gear buttons installed) limiting how far in it goes (or is it supposed to be slilghtly loose..?), but nothing could be found.

Corvette America has a good picture of the coupler, side gear, gear button & side gear washer (and all are in the distributor when it jams) and here are their numbers if you want to see what I have tried on two different housings with the same results.....X2601 Tach Drive Gear Assy....

If anybody has an idea please let me know, this is making me crazy

 

You may need to mill the button a tad.
On a side note, the Paragon parts fit the best.

 

Index the distributor correctly when you install it and you will not need the 90 degree connector.

 

Instead of using that 90 degree adapter just clock your distributor so the cable has a straighter shot at the hole in the firewall. I think there was even a service bulletin out on this by GM back in the day.

Ooops. Mike beat me to it!

 

Hi LB,
I don't know if you want to move the distributor in to the proper position or not.
If you do that will make the connection much simpler and direct but WON'T solve the problem if the cause is the distributor shaft or gear drive.
I'll post 2 photos and a page from the AIM to give you an idea of the proper clock for the distributor on a Corvette engine.
Regards,
Alan

Notice the position of the spark plug wires too.

 

There is a thrust washer that goes between the coupler and the distributor. It's #1284L in the illustration below.

You will have some noise from the gears, when the distributor is assembled correctly, it's just how much noise are you experiencing.

 

Dave Fiedler has a good servicing article on the tach drive distributor. http://www.tispecialty.com/articles/article6.htm

 

Alan, if nothing else was to come out of my posting this thread, your photo proves one thing I've been trying to confirm. That is that a previous owner has installed the incorrect distributor cover bracket on the right side of the engine. He not only put the wrong one on, they attached it to the incorrect manifold bolt. On my car, the right hand vertical bracket is under the last bolt on the manifold, not the "next to last" as your picture shows. That is why I could not index the distributor... I have now ordered the correct bracket and hopefully that will allow proper indexing from that point on.

 

That problem may be corrected, thanks to Alan's picture showing I have the wrong bracket on my engine, but I still need to know about the fitment of the cross gear & coupler. I would think that the coupler "should" be tightened down all the way (to keep it from moving, or allowing increased clearances on the main shaft & side gear) but if I do that, it locks the gear and will not turn. That is also the same issue on two distributors that I have, and one has had new bushing installed by High Tech Innovations and I doubt they would not have done the job correctly (noted in the article by Dave Fiedler) causing the issue. Even if they did not align correctly, that does not explain why the O.E. distributor also jams the gears if the coupler is tightened down. Also, as shown in Alan's picture, my AIM and aftermarket pictures, all the correct parts are there for the side gear and coupler, also the bushing in the distributor is an original GM one from my time with Chevrolet Parts (still have more with GM shims, points wires and some other parts)

 

Assemble it without the main shaft. If it binds, you need to mill down the button.
Assemble afterwards with bluing, and check the mesh. Should be close to center.

 

Are you aware that the GM button is nylon, not metal ? I will try assembling it without the main shaft to see what happens, thanks

 

out of curiosity where did you find a GM button?

 

I don't have the GM button but I do have a replacement teflon button that will work just fine...

But..

Installing reproduction side and main shaft gears is not as easy as it my appear.

First off... did you check the distributor bushings for play. You do this while running and you use a dwell meter... if the dwell opens when you torque up the engine then you have slop in the upper bushing.

Secondly.. it's rare that we get a set of gears and install them in a distributor and they actually work out of the box... The best way to tell if you'll have any issue is to rotate the distributor in both directions... it should move forward and backward without any binding what so ever... It should be smooth..

How do we accomplish this in house... I have a lathe... so if the gears are binding I can dress of a bit and then re-assemble and test again....

Other issues would be the brass button... If your distributor is correct, installing a brass button would be a mistake because it will cause the gears to bind. Use the teflon button that snapped into place in the side wall and you'd be set.

https://willcoxcorvette.com/corvette...n-62-74-teflon

The only time I use the oylite button in a distributor is when it's a 1969early or older distributor and/or if the side wall is worn out to a point where it needs to be milled and then the oylite button makes up for the wall thickness that I remove on the mill.

The distributor below has a oylite button installed inside it... but it was also machined down so that the button made the original side wall the original size. On your distributor you would have had a hole where the middle of that button is.. but inserting the oylite button will only make the wall too thick. the teflon button should make it the correct size and work considering you buffer the gears to mesh properly.



IMHO,

Willcox

 

If your using the nylon button and it locks up, surface grind or file the thrust washer. Give it .003" to expand when hot, or it will lock up and trash the gears.

 

To make sure I'm thinking of the same part, what is the thrust washer you are referring to?

 

The washer between the C/S gear and the coupling. Or alternately machine down the face of the coupling.

 

Normally, the issue is the cross gear is too long. The new cross gears have a brass end to them that always seems to cause a binding issue when installed. We dress the end down in the lathe to acquire the proper end play.

 

That's why the blueing. Have to see which way to go.

 

Wow, so I thought I had a pretty good grasp in my head how this laid out in my head, however now in finally getting around to do this, I took the old parts out, (tack gear). Inside I see the what looks to be old brass button, thought it just came out and replaced with the new one. No it doesn't come out. Is that the part you speak of to be drilled out and milled to accommodate the new button, or does that stay in plus the new brass button? Also, no sign of nylon button anywhere in the old system on mine. I had it in my mind that the new brass button sat in behind the gear with the flat side against the back distrib wall and the prong part of the button against the gear, now I think I am backwards on that, or am I? Wish I could draw a more specific picture and post what more clearly my question, but I guess easiest way is, what direction does the button prong face, to gear or drill out old and prong slide into the hole? I actually have the new assembly with both the nylon and brass buttons. I would be fine using whichever is easier, yet if I use the nylon I don't see how that snaps in either, which looking at it appears to just snap in a hole? To be honest, I don't think there was any problems with the old gear and not sure how to check for play, perhaps because maybe there was none, but had to take it out to check gear and all else, gear looks fine but since it is out I'll put new in. Perhaps you could show how and what direction both the nylon and brass button sits in the distributor and just what you are drilling and milling?. By the way, In adding the soft top to my 69, I had purchased the fastener kits for the weather strip from one of the other outlets. As I was doing it I was pulling my hair out in disbelief that they used so many washers and made putting it together ridiculous. I happened onto your online catalog looking for other parts and stumbled onto your kit. Ended up ordering it and can't even tell you how much easier and clean looking it was.

 

The brass button is typically used to repair the 1969 Early and older distributors that don't have the Teflon button. So if someone has installed one in you distributor I'd make sure that the button is flat to the inner wall of the distributor. The buttons when installed are pined into the housing when they are installed so if the wall isn't flat then you'll need to remove it. If it is flat then I'd go to the cross gear and index it appropriately. (I'm also just curious if you removed and replaced the bushings).

There are several things that will cause the cross gears to wear out and the main one is the bushings.

So, if the wall is flat to touch, then I'd go with it. But if the button is elevated to the wall then I'd remove it and install the Teflon button... That's the simple fix.

The gear when installed correctly should rotate freely in both directions.

If the button is elevated and you remove and replace it with Teflon, don't do anything to the cross gear until you do a test fit.

Willcox