different tach's???

[BUXMAN66]

i bought a tach dash off of e-bay (board member),and after doing some talking w/ the guy's at restoration world (full line of gm cars and trucks restoration parts)...and then his supplier.....american autowire......i now have been told that there might be a possibility that even w/ the correct style harness to hook up w/ my hei ignition...that gm had different styles of tach's and that some were only compatible w/ points/coil style of ignition. can anyone shed some light on the subject.....and also what the hell am i gonna do w/ a coil type tach...and i've got the hei style ignition?? any way of knowing/identifying this beforehand or is it just hook it up and hope??

[1969 GMC]

all 67-72 trucks had points style ignition. many people have converted their truck to HEI, and the tach works fine...sounds like the resto guys are blowing smoke up your a$$? you may have to wire the tach differently, but I dont know about this.

[jhow66]

What color wires does your tach have?

[BUXMAN66]

my thoughts exactly!! the guy at american autowire did give specific instances though....the early 60's years trucks, and others i dont remember exactly. he said the points style of tach read the pulse given off the coil...and that the circuitry was different......??

[BUXMAN66]

i haven't recieved the tach yet ......from the big brown truck!!

[jhow66]

What brand?

[BUXMAN66]

it's a factory tach dash check it out: http://cgi.ebay.com/ebaymotors/ws/eb...tem=2449136434

[jmanz69]

They all read the pulse off the coil. The HEI has a terminal that is labeled TACH. Just hook up the lead that would normally go to the (-) side of the coil and you are set. I think he may have been trying to get you buy something he has to sell. Whether it's a pionts or HEI, the tach is on the (-) side of the coil. It's the same reading, just a different location.

[s95930]

I think they are confused. When I use my tune up tach on vehicles with points and vehicles with HEI. I don't do anything other than hook up the wires. I assume the tach in the dash works on the same principle.

[jhow66]

Nice looking dash. Just finished a setup just like yours for my brother-in-law. Coil terminal on tach goes to tach terminal on HEI. Other terminal on tach goes to a 12 volt switched source. These tachs work with both HEI or points as I have installed both ways .

[BUXMAN66]

i don't see how he really has anything to gain by it but........i personally thought the only differences were a mechanical tach and a electrical tach.... there isn't any difference in the price for either harness.......whatever?!?

[BUXMAN66]

thanks to all w/ the replies....i don't just plop down $400 bucks everyday y'know?!!!lol

[Longhorn Man]

A mechanical tach would run off a cable like on the old 63 (I think it was 63) Corvettes and on many old deisel engines.

[Rooster's 67]

only issue you could have is there is actually a tach for 6cyl and 8cyl and they are different. the back of the tach will be stamped, mine reads 8CYL but very faintly.

[BUXMAN66]

everything's been taken care of...in fact i've heard from the guy that i bought it from and he assured me that it is the same tach that he has in his own truck,...and running a hei.

[GMC Jim]

If you want a tach that is just a little " different"..... Teleflex has a line of tachs used with marine engines.....Most are 6000/7000 RPM and are available in several styles, background plate colors etc....

[1972C10]

I had a really neat tach one time i got my 72 hooked it up the first day second day i upgraded to an hei it woudlnt work with the hei had to have the external coil ended up giving to a friend with a mid 80s ford. Some tachs wont work with hei mainly older ones.,

[Hooter]

they tachs are all the same same reguardless of 6 cyl or 8, there is a set screw in the back of the tach to select either 6 or 8 cyl

[1969 GMC]

the only different tach is the diesel tach out of a medium duty truck, which is only labeled to 4k, as opposed to 5k on all gas trucks.