Tach wire through firewall - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stope4 · 12-30-2008, 11:32 PM

I know this has probably been discussed but I have searched the site for two days can't seem to find the answer. I have a 71 and want to route the tach wire through the firewall. I know the hole is to the left of the bulkhead but I don't know what size hole I should drill. The Tach wire is from the typical tach wiring kit eveyone sells. Can someone answer this?

**LockDoc** · 12-31-2008, 12:23 AM

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Not off the top of my head. I just ran my wires yesterday but the hole was already there on mine so I didn't have a reason to check it for size. I will try and check it in the morning.

LockDoc

JimKshortstep4x4 · 12-31-2008, 06:20 AM

The hole size for the tach grommet is 3/4". Here is a pic of the factory hole.

Jim

tcb-1 · 12-31-2008, 08:41 AM

I just ran my tach harness wire a few weeks ago. I used Jim's picture as a reference and it was perfect! There will be a cardboard knockout you have to remove inside the cab as well. Then once the brown wire is through the bulkhead, it will run up to the plastic gutter, across the transmission tunnel, then down to the coil.

**LockDoc** · 12-31-2008, 11:22 AM

Quote:

Originally Posted by JimKshortstep4x4

The hole size for the tach grommet is 3/4". Here is a pic of the factory hole.

Jim

Thanks for posting that Jim... Saved me a trip to the shop. Now I can stay on the board longer...

LockDoc

stope4 · 01-01-2009, 12:06 AM

Yes Jim thank you very much. I plan to write the dimension on the tach page in my assembly manual since it references a page in UPC 1 that is not in the assembly manual.

ERASER5 · 01-01-2009, 02:56 AM

Or you could use the factory wiring block. There are empty slots ready to use.

12-30-2008, 11:32 PM	#1
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Tach wire through firewall I know this has probably been discussed but I have searched the site for two days can't seem to find the answer. I have a 71 and want to route the tach wire through the firewall. I know the hole is to the left of the bulkhead but I don't know what size hole I should drill. The Tach wire is from the typical tach wiring kit eveyone sells. Can someone answer this?

12-31-2008, 12:23 AM	#2
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,593	Re: Tach wire through firewall - Not off the top of my head. I just ran my wires yesterday but the hole was already there on mine so I didn't have a reason to check it for size. I will try and check it in the morning. LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

12-31-2008, 06:20 AM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Tach wire through firewall The hole size for the tach grommet is 3/4". Here is a pic of the factory hole. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC Last edited by JimKshortstep4x4; 07-14-2009 at 12:53 PM.

12-31-2008, 08:41 AM	#4
tcb-1 Nothing to see here..... Join Date: Jun 2007 Location: Shawnee, KS Posts: 4,625	Re: Tach wire through firewall I just ran my tach harness wire a few weeks ago. I used Jim's picture as a reference and it was perfect! There will be a cardboard knockout you have to remove inside the cab as well. Then once the brown wire is through the bulkhead, it will run up to the plastic gutter, across the transmission tunnel, then down to the coil. __________________ Doug THANK YOU to our American Soldiers & Veterans - POW MIA "You will NEVER be forgotten". The democracy will cease to exist when you take away from those who are willing to work and give to those who would not. Thomas Jefferson Last edited by tcb-1; 12-31-2008 at 08:44 AM.

01-01-2009, 12:06 AM	#6
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: Tach wire through firewall Yes Jim thank you very much. I plan to write the dimension on the tach page in my assembly manual since it references a page in UPC 1 that is not in the assembly manual.

01-01-2009, 02:56 AM	#7
ERASER5 Registered User Join Date: Jun 2006 Location: Indiana Posts: 4,859	Re: Tach wire through firewall Or you could use the factory wiring block. There are empty slots ready to use. __________________ '70 GMC C1500 LWB Power disc brakes. WooHoo! Posi 6 Lug Dana 60



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