Who's got a picture and hole size... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ChevyDude · 07-01-2006, 11:50 PM

for where the tach factory wiring came through the firewall? I know how it all wires in the cab and have a factory tach harness...just need to drill correct size hole in the correct location.

Thanks!

JimKshortstep4x4 · 07-02-2006, 06:36 AM

Here is a picture of the factory hole location on a 72 Suburban firewall. The hole for the grommet on the tach wire is 3/4" and is located between the bulkhead connector and the E-brake cable hole. There are "dimples" in the firewall for the location of the hole(s) to be drilled.

Jim

ChevyDude · 07-02-2006, 10:49 AM

Thank you very much Jim! Perfect pic of what I needed! Guess I need a 3/4" hole bit....Home Depot here I come!

Anyone adding a tach to a non tach truck....save this pic!!!

Alex

cckutchma · 07-02-2006, 11:00 AM

I recently purchased a painless wirin harness for my 84 C20 and also want to change out my warning lights to actual gauges and add a Tach. are there any good diagrams for that and where can i get the sending units a well?

72gord · 07-03-2006, 09:17 AM

In a 67 cab that hole is 1'' diameter...or at least mine is and it doesn't look like it has been drilled out.

JimKshortstep4x4 · 07-03-2006, 09:41 PM

The factory punched the holes as can be seen on the picture of the Burb firewall. I was not sure of the year that ChevyDude has so I made sure he knew that it was a 72. I did not have a 67 to take a picture of, so if yours is different, maybe you should post a picture of it as some of these details were changed over the years.

Jim

TugOwar · 07-03-2006, 10:51 PM

The tach wiring is,, one wire to the tach side of distributor cap?? Corrct me if I'm wrong. The end that plugs into the dizzy would fit through a .. 3/8" hole? 1/2" at the most? Why make a hole bigger than necessary? As long as you have a grommet to fit, I think I'd make the hole as small as possible. JMO

ChevyDude · 07-04-2006, 02:17 AM

Mine is a 71' and a 71' factory tach harness from M&H has a 3/4" grommet.

72gord · 07-04-2006, 07:49 AM

My truck is at the body shop right now...I'll get a picture of it next time I get a chance. In my LMC book 67 is a different part number for the tach wiring harness than 68-72, possibly just because of the grommet size?

07-01-2006, 11:50 PM	#1
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Who's got a picture and hole size... for where the tach factory wiring came through the firewall? I know how it all wires in the cab and have a factory tach harness...just need to drill correct size hole in the correct location. Thanks!

07-02-2006, 06:36 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Who's got a picture and hole size... Here is a picture of the factory hole location on a 72 Suburban firewall. The hole for the grommet on the tach wire is 3/4" and is located between the bulkhead connector and the E-brake cable hole. There are "dimples" in the firewall for the location of the hole(s) to be drilled. Jim Attached Images

07-02-2006, 10:49 AM	#3
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Re: Who's got a picture and hole size... Thank you very much Jim! Perfect pic of what I needed! Guess I need a 3/4" hole bit....Home Depot here I come! Anyone adding a tach to a non tach truck....save this pic!!! Alex Last edited by ChevyDude; 07-02-2006 at 11:32 AM.

07-02-2006, 11:00 AM	#4
cckutchma Junior Member Join Date: May 2006 Location: Springfield, IL Posts: 36	Re: Who's got a picture and hole size... I recently purchased a painless wirin harness for my 84 C20 and also want to change out my warning lights to actual gauges and add a Tach. are there any good diagrams for that and where can i get the sending units a well?

07-03-2006, 09:17 AM	#5
72gord Never enough time!! Join Date: Mar 2004 Location: sw Wisconsin Posts: 602	Re: Who's got a picture and hole size... In a 67 cab that hole is 1'' diameter...or at least mine is and it doesn't look like it has been drilled out.

07-03-2006, 09:41 PM	#6
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Who's got a picture and hole size... The factory punched the holes as can be seen on the picture of the Burb firewall. I was not sure of the year that ChevyDude has so I made sure he knew that it was a 72. I did not have a 67 to take a picture of, so if yours is different, maybe you should post a picture of it as some of these details were changed over the years. Jim

07-03-2006, 10:51 PM	#7
TugOwar Registered User Join Date: Sep 2004 Location: Pleasanton, TX Posts: 1,723	Re: Who's got a picture and hole size... The tach wiring is,, one wire to the tach side of distributor cap?? Corrct me if I'm wrong. The end that plugs into the dizzy would fit through a .. 3/8" hole? 1/2" at the most? Why make a hole bigger than necessary? As long as you have a grommet to fit, I think I'd make the hole as small as possible. JMO

07-04-2006, 02:17 AM	#8
ChevyDude Senior Member Join Date: Jun 2003 Location: Westminster, CO Posts: 3,071	Re: Who's got a picture and hole size... Mine is a 71' and a 71' factory tach harness from M&H has a 3/4" grommet.

07-04-2006, 07:49 AM	#9
72gord Never enough time!! Join Date: Mar 2004 Location: sw Wisconsin Posts: 602	Re: Who's got a picture and hole size... My truck is at the body shop right now...I'll get a picture of it next time I get a chance. In my LMC book 67 is a different part number for the tach wiring harness than 68-72, possibly just because of the grommet size?



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