I purchased and installed an MSD 8572 distributor this afternoon. Got everything back together, got the engine running and the initial timing set, but my tach drive has quite working. There was reference to the tach drive in the installation instructions:

When using a stock GM mechanical tach drive the supplied square tach drive adapter must be used.

To aid in the installation, the gear drive assembly can be removed and rotated 180* by removing the two allen screws. If this gear drive is reversed, a Reverse Rotation Tach Drive Gear Set, PN 8492 will be required.

No square tach drive adapter was in the box? We disconnected the drive until we can sort this out.

Any ideas?

 

Hmm, there should have been an adapter that you must install at the end of the tach cable. This adapter is bronze looking it attaches to the end of the cable and it has a small cross pin that goes into a slot inside the distributor tach port. Look for it it should had been in the box. BTW, you need to cut the tach cable by the length of the adapter.

 

I bought the same unit two weeks ago. I had to buy the tack-drive adapter separately. It doesn't come with the MSD distributor. You can go to Summit Racing's web site and do a search and a pic will come up.

 

I bought mine about two months ago and it came with the adapter.

 

Why would you have to do that? The square cable fits inside the adaptor. Also, no mention of this in the instructions from M.S.D.

 

Because the adapter will make the cable about an inch longer, but the cable housing is the same old length.
I first installed it without cutting the cable and it started to make all kinds of noises and erratic reading on the tach.....You can try it with out cutting it, it may work for you.

 

Thanks for the assist guys! The adapter was in the box, was looking for something larger. Will get that installed today, and get the curve sorted out.

 

Don't cut the cable....I have run several MSDs in corvettes, never once cut a cable. The adapter is just a small brass insert that slips over the part of the tach cable that goes into the distributor. It does not change the length of the cable....

Note it goes in correctly only one way, you can flip it end for end but it will not go all the way into the distributor like that....if you put it in backward it will make the cable seem too long as it will not seat all the way in as it should.

 

You are correct sir! Just finished the task, and things are back in order. The brass tube did not fit the cable at all. Had to file the flats on the tach cable to get it to fit the adapter, then slide it on, insert the adapter into the distributor (correctly oriented), and done. It's amazing to me that this isn't covered in the instructions from MSD!

Again, thanks for the assist, now on to the timing curve!