Where does the tach wire go through the firewall? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Thealien** · 06-26-2009, 12:44 PM

Like the title says. I have a nice tach dash to install and I have the wire with the grommet that goes in the fire wall. I want to know where the correct location for that wire to go through the firewall.

Thanks
Mark

**jaros44sr** · 06-26-2009, 01:35 PM

To the right of the fuseblock(standing in front of the truck) There are a whole bunch of factory detents running horizontal in this area and you can pick one to drill out. There is a pic around here, bin used alot, I'll see if I can find it

**jaros44sr** · 06-26-2009, 01:41 PM

It's on page 36, post #881 of my thread on the blazer side...sorry don't know how to do links

OldSkool71 · 06-26-2009, 02:08 PM

Mark,

Glad you brought this one up I am curious myself. I will be adding an original tach to my instruments as well and would like it to be as close to the original location as possible.

Ron

**jaros44sr** · 06-26-2009, 02:17 PM

On the Blazers there is a factory grommet in that location, I believe it is for the backup lights(brown wire)

**CPNE** · 06-26-2009, 02:45 PM

Look here

**Thealien** · 06-26-2009, 06:54 PM

Thank you!!

**Thealien** · 06-28-2009, 06:36 AM

Yesterday I tried to install the wire in that 3/4 inch hole and the hole is to big for the grommet that comes with that wire. Anyone have any pics of the tach wire installed in that hole?

There is also some extra metal on the inside of that hole but it is not flat so I don't think I could just drill that out to the grommet size?

jamesi20 · 06-28-2009, 07:19 AM

I had saved this picture on my computer and have no idea who to credit for it...

**Thealien** · 06-28-2009, 08:41 AM

That is the 3/4 inch hole I was referring to when I said it is bigger than my tach wire grommet. That picture is linked above in CPNEs post

**jaros44sr** · 06-29-2009, 12:34 PM

Quote:

Originally Posted by Thealien

Yesterday I tried to install the wire in that 3/4 inch hole and the hole is to big for the grommet that comes with that wire. Anyone have any pics of the tach wire installed in that hole?

There is also some extra metal on the inside of that hole but it is not flat so I don't think I could just drill that out to the grommet size?

Just measured my grommet for the tach wire and it is 3/4", pick a lower detent and use that spot?

**Thealien** · 06-29-2009, 12:51 PM

Quote:

Originally Posted by jaros44sr

Just measured my grommet for the tach wire and it is 3/4", pick a lower detent and use that spot?

Yours is 3/4 outside diameter or where the groove that holds it in place?

Where did you get yours if the groove is in fact 3/4 I would get a different tach wire harness if I can use that hole?

Thanks

**jaros44sr** · 06-30-2009, 12:53 AM

Quote:

Originally Posted by Thealien

Yours is 3/4 outside diameter or where the groove that holds it in place?

Where did you get yours if the groove is in fact 3/4 I would get a different tach wire harness if I can use that hole?

Thanks

Pretty sure it's the groove, but will remeasure tomorrow. I may have an extra one, since I ordered my engine harness w/ tach

**Thealien** · 06-30-2009, 06:37 AM

Thanks

**jaros44sr** · 06-30-2009, 09:55 AM

Yep, just checked! The groove is .750, +/- .020. My extra harness is for a coil setup, but can be changed for a HEI w/plug. LMK if you need it, just shipping, then this thread doesn't turn into a WTB and get locked

06-26-2009, 12:44 PM	#1
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Where does the tach wire go through the firewall? Like the title says. I have a nice tach dash to install and I have the wire with the grommet that goes in the fire wall. I want to know where the correct location for that wire to go through the firewall. Thanks Mark

06-26-2009, 01:35 PM	#2
jaros44sr Senior Member Join Date: May 2006 Location: Philadelphia, Pa. 19454 Posts: 9,761	Re: Where does the tach wire go through the firewall? To the right of the fuseblock(standing in front of the truck) There are a whole bunch of factory detents running horizontal in this area and you can pick one to drill out. There is a pic around here, bin used alot, I'll see if I can find it __________________ Semper Fi...Uncle Sam, you da man All parts offered to help are free, unless otherwise noted Dont try this stuff in my build thread, unless you have 55 years of mechanical OTJ training SAFETY FIRST AS usual, off topic They say your mind goes second, can't remember the first Jim

06-26-2009, 01:41 PM	#3
jaros44sr Senior Member Join Date: May 2006 Location: Philadelphia, Pa. 19454 Posts: 9,761	Re: Where does the tach wire go through the firewall? It's on page 36, post #881 of my thread on the blazer side...sorry don't know how to do links __________________ Semper Fi...Uncle Sam, you da man All parts offered to help are free, unless otherwise noted Dont try this stuff in my build thread, unless you have 55 years of mechanical OTJ training SAFETY FIRST AS usual, off topic They say your mind goes second, can't remember the first Jim

06-26-2009, 02:08 PM	#4
OldSkool71 C/10 CLUB MEMBER Join Date: Jul 2003 Location: Lakewood, CA Posts: 993	Re: Where does the tach wire go through the firewall? Mark, Glad you brought this one up I am curious myself. I will be adding an original tach to my instruments as well and would like it to be as close to the original location as possible. Ron __________________ -Ron-

06-26-2009, 02:17 PM	#5
jaros44sr Senior Member Join Date: May 2006 Location: Philadelphia, Pa. 19454 Posts: 9,761	Re: Where does the tach wire go through the firewall? On the Blazers there is a factory grommet in that location, I believe it is for the backup lights(brown wire) __________________ Semper Fi...Uncle Sam, you da man All parts offered to help are free, unless otherwise noted Dont try this stuff in my build thread, unless you have 55 years of mechanical OTJ training SAFETY FIRST AS usual, off topic They say your mind goes second, can't remember the first Jim

06-26-2009, 02:45 PM	#6
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	Re: Where does the tach wire go through the firewall? Look here __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

06-26-2009, 06:54 PM	#7
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Re: Where does the tach wire go through the firewall? Thank you!!

06-28-2009, 06:36 AM	#8
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Re: Where does the tach wire go through the firewall? Yesterday I tried to install the wire in that 3/4 inch hole and the hole is to big for the grommet that comes with that wire. Anyone have any pics of the tach wire installed in that hole? There is also some extra metal on the inside of that hole but it is not flat so I don't think I could just drill that out to the grommet size?

06-28-2009, 07:19 AM	#9
jamesi20 Senior Member Join Date: May 2002 Location: NORTHEAST OHIO Posts: 493	Re: Where does the tach wire go through the firewall? I had saved this picture on my computer and have no idea who to credit for it... Attached Images

06-28-2009, 08:41 AM	#10
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Re: Where does the tach wire go through the firewall? That is the 3/4 inch hole I was referring to when I said it is bigger than my tach wire grommet. That picture is linked above in CPNEs post

06-30-2009, 06:37 AM	#14
Thealien Senior Member Join Date: Jun 2007 Location: Pine Ridge Florida Posts: 4,134	Re: Where does the tach wire go through the firewall? Thanks

06-30-2009, 09:55 AM	#15
jaros44sr Senior Member Join Date: May 2006 Location: Philadelphia, Pa. 19454 Posts: 9,761	Re: Where does the tach wire go through the firewall? Yep, just checked! The groove is .750, +/- .020. My extra harness is for a coil setup, but can be changed for a HEI w/plug. LMK if you need it, just shipping, then this thread doesn't turn into a WTB and get locked __________________ Semper Fi...Uncle Sam, you da man All parts offered to help are free, unless otherwise noted Dont try this stuff in my build thread, unless you have 55 years of mechanical OTJ training SAFETY FIRST AS usual, off topic They say your mind goes second, can't remember the first Jim



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.