There was a thread here a while back, but I guess I forgot to print out the info sooooo:

Can anybody tell me the size and location of the hole in the firewall for the factory grommet used on a 70 B body with a tach? Pics?

I think it's right next to the bulkhead wiring block, but....

Thanks

Dave

Here is a picture....not sure on the size!

Thanks a bunch!

hmmm, not where I thought it'd be; is it a factory tach car? What is the cable directly opposite the firewall bulkhead connector?

Cheers,
Dave

I added a factory tach to my Road Runner many years ago. I had aquired an original tach harness, and used a set of calipers to measure the narrow part of grommet then bought a hole saw at the local hardware store to match. I don't remember the exact size, but 1/2" comes to mind. It was a common size and the grommet fit perfectly.

Thanks Paul; was it in the same location as the one in the picture above?

Dave

Blue and black wires next to gray tach wire are for the headlight door system on a 70 Charger. I am not sure about the other cable/wire you are questioning without having a look underhood.

This is where the tach hole is drilled on my 70 GTX. It's a factory tach car. The hole diameter is about .830".

Ahhhh; that's where I thought it should go as opposed to the grey car pictured above.....

Thanks!
Dave

Dave,

Here is another picture of a tach wire. It only adds more confusion. I guess I would like to see a few more unmolested cars to confirm.

Well, we have 3 different locations listed but three cars which people have stated are original tach cars have them in the same spot as the pic of the '70 GTX, so that location is in the lead so far!

Thanks guys; if anyone has any more info or pics; lets see 'em!

the holesaw is coming out in the next couple of days!

Dave

curious

Here's my February '70 LA built GTX - original tach hole.

The evidence is mounting...

Yeah, I agree: I'm just about ready to declare a winner!

Thank you to everyone who posted!



Dave

tach hole diameter 13/16"

Thank you.

Dave

This thread came to mind as I'm installing the wiring in my car...I have a factory tach (70RR) and and I have the hole between the bulkhead and the master cylinder as shown in some of the pics above so that's no problem.

What I'm confused about is in the new dash harness I have there are the black (w/red tracer)and blue (w/yellow tracer) wires that are fed thru a large conical shaped rubber grommet that someone above states is for the headlamps on a 70 Charger.

So on my car are these wires are just left to hang under the dash unused?

Thanks,

Paul

These wires are for 70 Charger only. They run the headlight motor to open the doors. You will not need them on a RR. New harness must be generic. I would tape up the connector and even possibly tape this entire pigtail to your harness under dash.