I was cruising yesterday in my 1973 and suddenly the tach went dead. I thought it me be the cable that went off or broke. So when I got home i checked the distributor and the cable was in its position, so other thing is the problem. So I disconected the cable started the engine to check if the drive in the distributor was spinning: Diagnosis no drive spinning, so I have a busted tach drive. Now I need feed back on how to dissasemble the tach drive, should distrubutor be removed to do this? Is it only the drive or should I check the distributor main shaft? Also what replacemnt parts you recommend OEM style ones or aftermarket ones that are made of bronze or ss?

 

Chances are both the drive gear and shaft are damaged,and yes it requires removal and rebuilding of the distributor.Given your location,you may want to consider either getting a replacement unit and rebuilding your original for a spare,or upgrading to a MSD or equivalent and getting rid of the points at the same time.

 

I forgot to menction my points were replaced by a Ignitor II module wich runs ok... as I wanted to keep original style tach drive. MSd offers a tach drive dist but is en the $300 range and up? I also saw on ebay other brand of hei dist with tach drive (i donn't recall brand) on the 150-200 range. Ever heard of them?

 

You can get a good tach drive HEI distributor for about $175 from Star Performance - I got mine about 7 years ago and it works fine. I'm sure there are other vendors as well.

 

Remove the brass from side of dist. and look inside and inspect the mainshaft gear.If it looks good you will probably have to but a new driven gear and a new brass coupler.Chances are the main drive is worn.

 

Is this normal that they die suddenly or other symtoms awares you that the drive is about to die?

 

it did wobled a bit but not much....

 

Its gear to gear so until the gears slip you probably wouldnt see much but a little flicker.

 

update 5-11-2009
got the parts to do the rebuilt on december..but this saturday I did the rebuilt. I went to a friend that is mechanic and he borrowed me the shop and tools to do the thing myself... he helped me a little in some parts but i did all..my goal was to get it satrted when the thing was finished...Thing that I sactisfactory accomplished....I took the dizzy appart clean it well, had to shim it in the upper part cause the petronix module was rubing the magnetic pickup on the rotor (guess that was the culprit for missfires at high rpm). Old shaft was shot the tach gear was almost gone and the cross drive was also shot with some missing teeth....(i´ll post some picks later). Then put it all togheter..slipped it in the engine cranck it and fired right up...then tuned with the light and good to go... What I find out was that the vacumm advance was hooked to a constant vacuum source of the carb edelbrock (the one in the front drivers side...) so we changed to the port on the passenger side and engine changed (no vacuum at idle but increased while giving throtle) ..it runs smoother (guess that that also caused bad comsuption)...
Test drive great.. car runs lighter, tach reads ok, it bounces a bit when you pump gas on neutral but reads strong while going on a continuios acceleration...
And more important it quitted missfires at high rpm...I went the whole range up to 5-5.5k and it ran perfect...in 4th gear I put it to 120mph (don´t recall exact rpm but it was in the 4.5-5k) it had more to go but highway was short and some cars around....