[azbirds]

I have a 72 T/A that came with the unitized distributor. Will that tach work with an HEI unit? Don't want to hurt it experimenting.

[Peter Serio]

That tach should work on GM-HEI, if it is still functional. Why don't you post a photo of the back of the tach & I could tell you for sure.
I need to see the 2 plug-in tabs on the back of the tach right near the outer edge of the printed circuit.

[azbirds]

Ok, I'll take it out for a photo.

[azbirds]

So I finally had time to take out the cluster and take a picture.

[Peter Serio]

That circuit board is compatible with GM HEI. The 2 wires, one is 12 volts power (fused) with the key on and the other is the RPM signature wire that plugs into the edge of the top cap of your HEI distributor.

One of the tabs is labeled (molded into the black plastic cover) TAC or "TACK."

[azbirds]

Thanks!! I'll hook it up and see what happens.

[azbirds]

Thanks!! I've got another problem now. The stinkin needle fell off!!�� You are the one that rebuilds them, correct?

[Peter Serio]

At this point the meter is probably ruined. I am sending a sample meter to Hoyt next week for evaluation & to see if it's feasible to make some new ones. I have currently in production new meters for 65-67 GTO as well as 68 to 72 GTOs. I am not a big fan of all this cheap reproduction crap that's coming in from overseas. If I can get them made they will be identical to the original movement and it will be a part made in the USA by American workers. The original meters in our old GM car tachometers are balanced via springs and weights to gravity. The white pointer, attached, as well as the aluminum extension tube in-between the pointer and the moving coil is all part of the balance.


Because zero on the 2nd Gen trans Am tachometer is in a forced or unnatural position; 2 copper springs are what it needs to return to zero when you turn the engine off. Those 2 springs are wound in concentric circles. Once those 2nd Gen meters age the copper springs in them will get weak and the movement is sluggish and/or fails to return to zero. This is a very common problem with these tachometers now. I did notice that the paper inspection sticker is missing off of the back of your tachometer. This is a HUGE problem with these tachs!!!! That open hole in the blue plastic is for final inspection and tweaking of the weights when the meters are going thru quality control. After the part is passed QC, they put this thin white paper sticker to cover up that hole. Over time the sticker either falls off or disintegrates into powder or dust. Once this happens lint, road dirt and dust can easily enter into the magnet area with the moving coil. The area in and around the magnet is suppose to be a 100% clean zone. Any foreign material even a tiny piece of carpet fiber, lint or dust will be attracted by the magnet.

The air space in between the coil and the magnet is around .006 to .010" Once there is no covering left (the sticker) tiny pieces of debris eventually clog the air gap and your tach will stick and/ or not respond. That hole in the back MUST BE COVERED!!!!! ON a few early 70s tachs I noticed an aluminum sticker, but most of then are cheap paper and they don't last more than 7 or 8 years. I am not sure why GM didn't give The Trans Ams a plastic cap or snap-on cover for that opening.

[azbirds]

I've got a void in my cluster now. I guess I'll put a late 70's one in for now, but it won't be the same.

[Peter Serio]

I am going to try and get some new meters made, it is a long and costly process. I like to try and use US companies for my parts. But it's not easy.