Factory tach question(s)...

CompSyn

CompSyn

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...for 1969 Road Runner:

1) On the dash side of the firewall, does the tach wire integrate into the dash harness or is the tach wire independent from the dash harness?

2) What size O.D. is the firewall penetration for the tach wire grommet?

Thanks!
 
CompSyn said:
...for 1969 Road Runner:

1) On the dash side of the firewall, does the tach wire integrate into the dash harness or is the tach wire independent from the dash harness?

2) What size O.D. is the firewall penetration for the tach wire grommet?

Thanks!
Click to expand...

Okay, looks like Year One answered my first question -> https://www.yearone.com/Product/1966-74-a-b-e-body/hu6869

Still curious if anyone know the answer to the second?
 
Sorry but I never thought about measuring the hole when it was apart and I don't have a picture of the hole to guestimate from either
 
69hemibeep said:
Sorry but I never thought about measuring the hole when it was apart and I don't have a picture of the hole to guestimate from either
Click to expand...

Okay, well I did end up buying the M&H repro tach harness. I'll just measure the grommet that comes with that.

I was hopping by chance that a half inch knock out punch would be the magic size to get a clean factory like cut. If it's an odd ball size guess I'll use a stepped drill bit. It's the last thing I wanted to do is drill on my unmolested fire wall.
 
If you look you will find a very small rubber plug where the factory would have run the wire thru without the connector on.I pulled that plug out and used a vari bit on my drill and enlarged the hole to fit the rubber grommet that came with the harness.
 
red 69 runner said:
If you look you will find a very small rubber plug where the factory would have run the wire thru without the connector on.I pulled that plug out and used a vari bit on my drill and enlarged the hole to fit the rubber grommet that came with the harness.
Click to expand...

As I recall, my firewall has a dimple where the tach wire grommet should be. I just got my reproduction M&H wire harness from Year One. The grommet with this harness measures roughly 0.860" inch. A 7/8" inch knockout punch measures 0.885" inch which may be about right. I'll test it on some scrap sheet metal first to see how well the grommet seals. It would still be interesting to know exactly what the factory measurement is?

A pic of the factory install ->

69_Tach_Wire_zps17304834.jpg

69_Tach_Wire_zps17304834.jpg
 
I just put in a Year One harness in my 69 GTX. I used a 7/8 hole saw and it fit the grommet perfect. Loose enough to get the grommet in easily but tight enough to hold.
 
There is an orange wire with a male bullet in the tach harness for the tach lite. Is there a female terminal somewhere in the harness for it. I haven't been able to find it.
 
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