Moparts

Firewall grommet hole for tachometer

Posted By: 340clone

Firewall grommet hole for tachometer - 10/22/17 06:28 AM

Can anyone post a pic of the correct location for the firewall grommet hole for a tachometer on a '72-'74 B-body? (Or describe the exact location)

I know that '71 uses an existing connector on the firewall harness plug, but later years are supposed to have a dimple somewhere on the driver side firewall that marks the spot.

Thanks!
Posted By: NachoRT74

Re: Firewall grommet hole for tachometer - 10/24/17 04:37 AM

Actually as far I recall, 74s also uses the only cavity left empty on NSS harness plug. 72/73 uses the grommet. There are couple of threads with this info at FBBO board, just can't post the link right now.
Posted By: dart4forte

Re: Firewall grommet hole for tachometer - 10/24/17 06:37 AM

Here ya go

Attached picture 71 B Body Firewall.jpg
Attached picture 71 b Body Tac Grommet.jpg
Posted By: 340clone

Re: Firewall grommet hole for tachometer - 10/26/17 06:38 AM

Thank you! What year cars are the firewall pics from?
Posted By: dart4forte

Re: Firewall grommet hole for tachometer - 10/26/17 07:06 AM

71 Road Runners
Posted By: T2R9

Re: Firewall grommet hole for tachometer - 10/26/17 12:11 PM

Here is a picture of my 71 Road Runner engine compartment. You can see the plug just to the right of the master cylinder next to the bottom of the clutch reinforcement plate.

Attached picture IMG_0534 (Medium).JPG
Posted By: 340clone

Re: Firewall grommet hole for tachometer - 10/26/17 05:14 PM

Thanks for all of the photos! I was able to reference a '73 Charger with a factory tach and the hole with plug was in between the M/C backing plate and the harness block. On my '74, the harness plug that goes through there contains all of the A/C wiring that goes out to the engine bay. Must have been a change after '73. Does any one happen to have access to a '74 that may have had a factory tach? Thanks!
Posted By: 71birdJ68

Re: Firewall grommet hole for tachometer - 10/26/17 07:16 PM

Those aren't 71 B bodies.
Posted By: dart4forte

Re: Firewall grommet hole for tachometer - 10/27/17 01:51 AM

Originally Posted By 71birdJ68
Those aren't 71 B bodies.



Yes sir, I stand corrected. Had to look again. I got the pics off a 71 B Body site.
Posted By: 71birdJ68

Re: Firewall grommet hole for tachometer - 10/27/17 02:12 AM

Just didn't want to confuse the OP.
Posted By: NachoRT74

Re: Firewall grommet hole for tachometer - 10/28/17 04:53 PM

Originally Posted By dart4forte
71 Road Runners


imposible... thats A or earlier B, never 71 and later B
Posted By: 71birdJ68

Re: Firewall grommet hole for tachometer - 10/28/17 04:55 PM

We got it straightened out. Actually an E body would be the same I would think.
Posted By: NachoRT74

Re: Firewall grommet hole for tachometer - 10/28/17 05:00 PM

Originally Posted By 340clone
Thanks for all of the photos! I was able to reference a '73 Charger with a factory tach and the hole with plug was in between the M/C backing plate and the harness block. On my '74, the harness plug that goes through there contains all of the A/C wiring that goes out to the engine bay. Must have been a change after '73. Does any one happen to have access to a '74 that may have had a factory tach? Thanks!


74 bulkhead disposition, cavity 4, NSS harness BH plug

As mentioned, just 72/73 are with grommet. 71s uses the engine harness plug cavity left, since AC uses the two left free on NSS harness plug ( these doesn't get the NSS ground into the cab like post 72 cars )



Attached picture IMG_3923.JPG
Posted By: 340clone

Re: Firewall grommet hole for tachometer - 11/07/17 04:13 AM

Well the mystery is solved! I had already bought the grommet type, thinking it was for a '74 so I will just drill a hole for it and make it look as factory as possible.
© 2024 Moparts Forums