Downdraft

Car was running well, then today my tach started acting erratic and clattering first I disconnected the cable on the tach side, (MSD with the brass adaptor) to see if it was all OK then behind the tach - now I notice. When the tach cable was inserted all the way the tach would not budge - when it was barely inserted (but not secured with the nut behind the tach) the tach worked fine - as soon as I would tighten it would stop. After fiddling around sometyhing happened - now when the car runs the tach drive in the distributor no longer spins - I guess there is a gear inside the distributor? Will call the MSD help line on Monday - rev limiter will get me though the weekend. Should have left it alone .... Grr......

larrywalk

How large is the square drive hole in the distributor compared to the square end of the tach drive cable? It may be so loose that the cable to the tach is not turning.

KC John

That is what I had happen with mine. Over time the hole in the gear got sloppy and I replaced the gear and it worked perfectly. You can check to see if the end of the cable is still square, but they don't usually wear compared to the gear.

Downdraft

The tach worked fine for a while - now if I don't attach the cable to the tach and the engine runs, the tach piece does not spin - with or without the brass adaptor. Something inside the tach must be broken.

KC John

Sorry, I should have been more clear. The piece I'm talking about is in the tach. The other end of the cable is also square and goes into a gear.

This is the part I'm talking about.



You can get it with or without the brass sleeve.



Check this web site and you will see your options if that is what you find you need.

http://www.ecklerscorvette.com/catal...+gear&x=25&y=7

larrywalk

Downdraft, you are correct - with your last comment that "the tach piece does not spin" indicates that the cross gear is stripped where it meshes with the distributor shaft. When this happens it also destroys the gear on the distributor shaft itself - it too, will need replacement.

http://www.ecklerscorvette.com/catal...shaft&x=20&y=6

Downdraft

Do I need to replace the distributor shaft or can I find only the gear that goes on the shaft?

JohnZ

The mainshaft drive gear is an integral part of the shaft. When the gear fails, it also takes the steel gear on the end of the cross gear with it, and both get torn up; photo below shows a typical failure. If yours looks like the photo, you'll need a new mainshaft and a new cross gear.

Downdraft

Can I use the main shaft from my 327 - is it the same as that of the 383? Anything I need to check for?

What about the debree from the grinding gears, did it go in my oil?

wmf62

yes on the 327 shaft, and the debris should have stayed in the distributor housing as there is no oil flow through the distributor like an FI distributor. even if it did i wouldn't worry about it as the debris is small and it usually happens over time and the oil filter would take it out..

Bill

Downdraft

Thanks Bill

wmf62

i'm not sure if you were speaking about the stripped distributor being a stock GM as you said something about MSD, if GM, then yes, as a matter of fact your entire 327 distributor will work.

if not GM, then probably not..
Bill

Downdraft

Problem solved - it was just the pin. The tach drive gear was not lubed through the grease nipple - the pin had snapped. Reinstalled with a new pin, lubed, set the timing at 38° at 2,500 rpm and it runs like a champ!