Firewall rubber grommet

[Dino]

I need to run a 1/4" thick wire through the firewall and was looking at this grommet near the bulkhead connector and starter relay.  I removed it and the hole is just a hair over 1/4" in diameter.  I thought this was for the tach wire but then found that if your car didn't come with one (and mine didn't) then there would be no hole.  So it seems the tach wire should go where the dimple is, above and to the right of the grommet.  So what's the grommet for?

[Just 6T9 CHGR]

Damn good question Dino.  The tach grommet is indeed where the dimple is on the firewall.

Think of it as a gift from the Mopar Gods to you....now you dont have to drill a hole! 

[timmycharger]

Im thinking it used to be a firewall insulation nail hole that was converted to a wire passage with a grommet?  

[69RTSE]

On 66-70 B-Bodies with A/C these are rubber plugs that are located in three positions.  By the Bulkhead connector, above the accelerator pedal and above the water valve.  These are a bullet shaped rubber plug.  I have some links below that show these plugs very well.

http://www.hoffmanswinnerscircle.com/69rtconvertible/Images2/Firewall_RH.jpg
http://www.hoffmanswinnerscircle.com/69rtconvertible/Images2/Firewall_LH.jpg

Additionally, you are correct that the lower dimple is the hole for the Tach harness.  Except, if the car has cruise control and a tach, then the lower dimple is for the cruise control harness and the upper right dimple is for the tach harness.

Hope this helped.

[Dino]

Thank you much for that info, that really helps!  I hadn't considered the cruise control access.  That's something I'd love to add but prices for a 69 lever alone are getting way up there.

For now I'll use the existing hole to run the 8 ga wire through.  If ever I add anything I can always revise.

Thanks again