pnewt

Getting into areas with my 68 that are a bit above my experience level!! Hoping some of our experts can help with the education process. The original tach in a 68 would have connected via a plug or otherwise connected to the distributor. The 427 in my car has an HEI and it is not connected. The only wires near the HEI are a plug and another single wire. I have a new HEI with a tach drive connector(screw on) What do I need to do to make the tach work? Shouldn't one of these hook up to the original tach?? Thanks in advance for any help Thanks Paul

ctuinstra

Should work if it's a distributor with the tach drive built in. Very simple, just rotate and push the tach cable in and screw it down tight.

pnewt

So I assume the current HEI which has a side connection(marked) just plug in the cable end to it? The new one has a screw on connector so wont work? I sthe wire just a 1 wire with a spade on it? have to look closer as all I see are a 2 or 3 prong plug and another single wire which may have something to do with the wiper motor nearby. Sorry to be not much with this wiring stuff!!!!

Zoix

Your tach is mechanical it runs off the distributor via a cable. The new distributor has a tach drive so you plug the tach cable (like your speedo cable) into the threaded spot on the distributor. The tach should work; if it doesn't then your cable is bad or your tach is. Hook a drill motor to the cable & have someone in the car while you run it you should see it spin up if not the problem is between you& the tach. Make sure there is a drive gear in the distributor to plug your cable into. Good luck.

pnewt

last question. The tach cable(original) would have a thread on to the tach and a wire on the engine end to plug into the HEI. I could buy a new cable if the wire is no longer there. OR I could put in the new HEI and get a new cable with the threaded end both sides . The original HEI works fine and if I can get wiring right I should be fine. I just wanted to switch from a black cap to a red one with the new red plug wires

CanadaGrant

The wiring has nothing to do with the tach. It is completely mechanical and works off the cable only. The cable connects to the base of the distributor just like your speedo cable does to the trans. No wiring whatsoever is needed or used for the tach.

pnewt

Thanks everyone,think I've got it now.