Tach drive gear in pieces

[gary wilkerson]

I was driving home the other day and noticed the tach started hoping. I was only several miles from home so I didn't pay much attention to it UNTIL! I lost power and the engine bickfired a couple of times.
I shut it down and went and got the trailer.
I found the tach deive gear had come apart and must have let some pieces get lodged in the dist. between the shaft and housing.
The dist. had turned.
What do I do? I need to repair the dist. but what then? Do I have pieces in the oil pan? Do I just change the oil and forget about it?

Any help would be appreciated!

[Joe L.]

Re: Tach drive gear in pieces

Gary-----

Usually, when a tach drive and/or driven gear "disintegrates", the pieces will remain within the distributor housing. It is possible, though, for some to "sneak out" the 1/2" hole near the base of the housing vertical section. VERY unlikely, though, since the distributor shaft rides very close to the inner surface of this hole and will, itself, prevent debris from falling out into the engine.

What you need to do is to remove the distributor and rebuild it. You'll need, at a minimum, a new mainshaft and new cross gear. Also, if the distributor housing is not fitted with a thrust button for the cross gear, you should add one of those. I'd also recommend replacing the upper and lower bushings. Don't attempt this part of the job yourself, though. I recommend sending it off to Hi-Tech Innovations in FL for the installation of new bushings AND jig boring them to precision alignment.

[Ed Jennings]

Re: Tach drive gear in pieces

The same thing happened to my 71 BB when it was a pretty new car. I just disconnected the tach, timed it by ear, and drvoe it home. I repaired the distributer, set the timing and drove the car for another 50K miles before trading for a 280Z. I didn't change the oil immediately, but maybe I should have. The gears really weren't torn up too badly, just enough to lock the distributer.

[Gary Wilkerson]

Re: Tach drive gear in pieces

Thanks Joe and Ed,

I'll remove the tach and send it off. I'm not in a real hurry to get it back on the road.
But I will change the oil. It's cheap!!

Thanks again

[Ed Jennings]

Addendum

I should add that when I made my roadside repairs, I removed the crossdrive gear before I restarted the engine No teling how far the distributer would have rotated if the tach drive cable hadn't stopped it.

[LONNIE WIGGINS]

Preventive Maintenance???

You know, this sounds like the kind of problem that you just don't want to have to deal with :-( .

How about preventive maintenance? I don't know the details of construction here, but would it be practical/necessary to replace the gear, on some mileage basis, before it self destructs and screws everything up?

[Ray C.]

Re: Tach drive gear in pieces

I was shopping for a replacement distributor for my 1965 250HP at Carlisle Corvette meet and came across a vendor that sold mostly distributors. I explained how the original distributor tach drive gear had worn a spot in the back of the main casting and that I was looking for a brass bushing that is used to prevent the gears from becoming misaligned and destroying the gears. He stated" I use JB Weld on casting at the rear of the tach drive gear and fill it smooth. I have never had a returned distributor." I tried this process and the distributor and the tach drive are working great. I plan on checking for wear at the end of this driving season. Has anyone repaired a distributor using this method?

Ray

[Clem Z.]

Re: Preventive Maintenance???

the ones i have found had the cross gear tighten up in the bronze housing. they now sell a needle bearing one in the aftermarket to prevent this.i would guess taking out the cross gear and lubing it regularly would help. i always used moly kote when i put them back.