What will it take to run an HEI ignition with a Stewart Warner 970 series tach w/the seperate sending unit? (The tach and sending unit are both NOS)
Is there anything "special" about running this combination ? Any help would be greatly appreciated.

Kent
'68 Malibu ZZ502/502

Connect the sensor wire that usually goes from the box to the negative side of the coil to the "tach" terminal of the HEI, you should be fine if the batteries in the sender are OK. 970s are real old-school.

For a 970 tach you need the correct sender. There were 3 different ones produced, 1 for standard ignition, 1 for electronic and 1 for magnetos. There are no batteries in the sender. Don't have the model numbers of the senders here at work, but have info at home and install directions if you need help.

As far as being old school, should be just about right for a 68. Originally installed the tach I have on a 68 Camaro 396. Would be interested in whether tach will work with Standard Ignoition sender on a HEI as well. Would look good on the column of my 64.

Best of luck..JimC

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The sending unit I have is a 990 "B". Which I believe is correct for a Chevy ignition.
Jim, you are correct. There are no batteries in the sending unit. It is sealed. You also mentioned 3 different senders, one being for an HEI ignition. Could you verify that information ? If your instructions have a part number for the HEI sender, could you let me know ? I do not have the tach and instructions here with me, but will verify when I get home.

Thanks again,

Kent
'68 Malibu ZZ502/502

Kent

Did some checking last night, I guess my memory is getting foggy.

There are two models of the tach, a 970 for 12V negative grd and a 972 for 6v negative grd.

There are only TWO senders a 990-A for various TRANSISTOR ignitions system and a 990-B for standard points type ignition. There is also a 4-6-8 cylinder connection inside the back of the tach.

There is no reference to HEI systems as they did not show up for a few years.

The hook up for the 990-A is between the amplifier and the coil in most of the variations given, as this was set up for various transistor and magnitio ignitions available back then.

The 990-B connects on the distributor side of the coil. The sender is clearly labelled with the only notation that the battery connection should go to a switched power source giving a full 12v, but not the radio circuit due to the possability of interference. The light connection goes to insturment panel lights.

The white wire from the tach goes to the light terminal on the sender, the Green to the Tach, the Black to the ground, the red to the battery.

Don't know how this unit will work with a HEI dizzy, but sure would be interested in the results of connecting to the Tach lead of a HEI using the 990-B sender, You guessed it, that is the sender I have as well.

I think these units are getting quite rare and may be next to impossible to obtain a different sender. I have send inquiries to SW re this unit with no reply.

Let me know what happens, and good luck.

JimC

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Jim,

Thanks for checking. The instruction sheet I have says the same thing. But unfortunately, I'm still not sure if I can run this setup with the HEI. And as EXPENSIVE as this tach is, I'm not about to "burn it up" by trial and error. Perhaps a repair shop that specializes in tachometers would be of some value.
Well, I do appreciate you help. BTW, nice car ! http://www.chevelles.com/forum/smile.gif

Kent
'68 Malibu ZZ502/502

Please let me know if you find anything out on using it with a HEI. While my tach was not very expensive, I seem to recal $45 in the late 60's, would hate to burn it up just to try it. Know what they are worth.

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http://www.chevelles.com/feature/jan99.html

Jim,

(Hopefully this message finds you) I had my tach and ignition monitor "upgraded" by D&M Restorations. Apparently they were back-logged with work, but were finally able to finish mine. The tach is now calibrated and able to run with or without the ignition monitor (my choice !). The car is not done yet, so I cannot comment on how it works. Hopefully by summer.

Kent
'68 Malibu ZZ502/502