More tach wiring confusion...please enlighten dumbdum

[MAC71Cheyenne]

This too should be so easy...
Factory tach, Summit spark box, HEI ignition, American Autowire harness, contradicting information. Double taps on the pink wire go to fuse box always hot, correct? The second pink wire tap goes to? The grey wire I believe should go to the cap marked tach but Summit's information says connect this to their grey wire from the box...???
So the ground for all this is??? Just want the dang tach to work without burning anything up. All the original wiring for the tach was gone and wiring this for dummies is not bookmarked.

[Andy4639]

Not sure about the box wiring. Will need more info and wiring instructions.

Factory tach with a HEI is as follows though:

Pictures are of a old tach & new one.

Back side of tach terminals. 1 is marked 12 volts, it goes to the fuse pane block 12 volts when running & cranking the truck. I put a 5 amp inline fuse in it also.

The other terminal on the back of tach is marked coil, it goes out to the HEI distributor and hooked to the Tach terminal which is marked for it.

3rd picture shows a factory tach cluster with factory harness which is separate from the cluster harness.

[MAC71Cheyenne]

Andy, I have the factory tach with the lugs. It's plug

[MAC71Cheyenne]

Andy, I have the factory tach with the lugs like your 2nd pic. Plugged in. My pics suck but the Summit instructions are attached. Knowing what I do now I would have just pulled an 80'sish GM hei and been done with it.
Tablet's not letting me attach the second one...yet

[Andy4639]

It looks like you remove the HEI cap and take the module out of it and replace it with what came with the box. Correct?

If so then the tach should just plug into the grey wire to the connection on the back of the tach marked coil. Then the other should go to the fuse panel as always. Best I can tell.
Can you get a better clearer picture of the directions? When I try and en large it it blurrs out.

Is this it? #8 in the drawings, top half.

https://static.summitracing.com/glob...sum-850602.pdf

[Andy4639]

Ok, I took a picture of the box schematic and down loaded it and here it is. You should be able to follow this and it should work. LMK what you think. The tach wire you have coming off the tach should go to a YELLOW wire out of the Summit box. The 12 volts should be like factory unless the box states other wise.
Question for you? Why do you need the box? If your using a HEI then why the box?
Second ???

Knowing what I do now I would have just pulled an 80'sish GM hei and been done with it.

Are you not using a HEI now?

[MAC71Cheyenne]

Per Summit...

[Andy4639]

Per that last drawing. Tach coil wire goes to grey wire. The 12 volts on the tach is just like factory goes to 12 volts in fuse block are wherever you want to hook it to as long as it supplies 12 volts while the truck is running. Everything else is hooked as directed in Summit directions.

[MAC71Cheyenne]

Thanks Andy. Going to finish installing my new/old '67 steering wheel then button up this mess.
As Mad Magazine's Alfred Nueman used to say, "what, me worry".

[Andy4639]

Originally Posted by MAC71Cheyenne

Thanks Andy. Going to finish installing my new/old '67 steering wheel then button up this mess.
As Mad Magazine's Alfred Nueman used to say, "what, me worry".

You show a HEI picture in your post, which are you using, it are a Summit distributor? Just wondering. Hope you get it straightened out. A over all picture of the setup could help figure it out also of the distributor you are using.

[MAC71Cheyenne]

I have Summit's SUM-850001R dist installed. It had a GM HEI that was trashed. Gear was wore, vac advance junk. Not to dis Summit at all but if there is ever a next time I'm going with new or rebuilt GM dist. Learning as I go. This is my first run with the ball in 40 years on working on these things. Lots to remember, don't have the stations Chilton manuals, memory and my Chevy elbow is is skipping a few ratchet stops these days. That is why this bunch is a great clan. If you don't know how or can't remember, someone else does and is willing to tap in.
Being most of the trucks are 50+ years old and many of us older than that. With pulling in something that has been sitting outside for years, doesn't run, or like in my case screwed up prior to acquisition most of us couldn't do it alone. Appreciate you taking the time and helping out.
Just about done with the steering wheel and will finish up the tach connections. Let yah all know the end results...

[MAC71Cheyenne]

You pegged it Andy! Made the connections, connected the battery, and fired it up. Works PERFECTLY.

[Andy4639]

Originally Posted by MAC71Cheyenne

You pegged it Andy! Made the connections, connected the battery, and fired it up. Works PERFECTLY.

Good deal sir! I like happy endings.