Stratos

Need direction, I have had my Tach rebuilt 3 times by a restoration shop, each time I install the tach the cross gear breaks right in the middle after about 30 seconds. The shop replaced the shaft and made sure the play was in spec. They have not charged me for the multiple rebuilds. The tach cable was replaced, the tach is free and no binding is occuring, I can manually rotate the cable while hooked up to the tach and it feels free, I can drive the tach with a drill and it looks fine. I'm about to give up on this distributor and by a reproduction. If I go this route should I upgrade to electronic with a mechanical tach drive? What manufacturer would you recommend..My car is a 1972 with the base 350 (modified a little) and 4 speed.

Guru_4_hire

I have been dealing with this myself

Here are the options I have found
for a hundred bucks you can replace the parts in the distributer with the pertronix ignitor

For 2 undred bucks you can get a new dual points distributer with tach drive

for 3 hundred bucks you can get a mallory unilite

for 500 bucks you could get a mSD distributer with a tach drive

for 540 you can get an HEI ignition with tach drive from midamerica

Desertvette

I've never heard of the cross shaft breaking in two. Usually the distributor main shaft gear get stripped out from the cross shaft moving back and forth until it binds and wipes out the gear.
Remove the tach drive bushing/cross shaft and see if there is a button at the bottom of the well or if you have a set screw in the distributor body opposite the cross shaft.
If not, that's your problem and I think it's time to find a new shop or do the repair yourself. While your in there ,carefully inspect the condition of the main shaft gear. If it's damaged at all your looking at a new main shaft along with the cross shaft

Stratos

I'll look for the set screw tonight, the cross gear has broke all three times right in the middle and there doesn't appear to be any damage to the main shaft gear such as stripping. The shop I'm using is a corvette only restoration facility and dam big. The owner rebuilt the distributor the last time and is scratching his head, quote: I've rebuilt hundreds of these and have not seen the cross shaft break like that before. By the way, what is the set screw for? Is it used for setting the gear to gear contact ?

mrvette

Strat, my memory is clear on this from the olde tyme daze, and I can assure you the lifespan of a dist driven tach was about 2 years if you were lucky...ALL the vette mechanical tachs based on a speedometer mechanism were frought with failures, and high cost/repairs....

I never even considered anythng but an electronic 75-77 tach and HEI distributor well before even the TPI was installed....

seems to not matter a whole lot what is done with the mechanical tachs, the lifespan is short....and they ain't cheap either....vs my electronic changeover has been fine...knock on wood....

GENE

Desertvette

The set screw was a mod that I picked up from Corvette News 30 yrs ago. You basicly drill and tap the dist body opposite the cross shaft end. Install the set screw until it hits the gear and back up 1/4 turn. My current distributor is 35yrs old and although I've just recently overhauled it, the cross shaft and main shaft gear never failed. I also kept the gears lubed with high temp bearing grease
The set screw keeps the cross shaft from walking back and forth. An alternative fix to the set screw is installing a brass or plastic button in the bottom of the well. The Zip catalog has a good picture of the dist and set screw and they have all the parts including buttons if you want to go that way and not drill the distributor.
There's also the possibility your dealing with a batch of defective cross shafts. Being that this is a large shop they may buy there parts in large quantities and this could explain whats going on. Try another vendor for the next cross shaft. LOL
Bob


[Modified by Desertvette, 10:29 PM 8/27/2003]