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1937 Firewall hole I.D.
#1355432 Wed Apr 15 2020 11:02 PM
Joined: Nov 2012
Posts: 140
B
Shop Shark
Hello Stovebolters,
Today I began filling the un-used holes in the firewall of my 1937 GMC. There are several holes that I am unsure of originality or purpose. Any help would be appreciated.

Here is a picture of my firewall. https://photos.app.goo.gl/wJ4yx6C5ZkPFAYvu6
In the photo I have numbered the holes and below I've listed is what I think the hole is for. If anyone has information on this firewall please let me know.

Hole #1 is for GMC only hood props.
Hole #2 and 2a I think are added by prior owner. Maybe for a voltage regulator and wiring harness?
Hole #3 is for vacuum line to wipers?
Hole #4, and 5 unknown.
Hole #6 is for coil wire.
Holes 6a are original and unknown purpose.
Hole #7 is for the Canadian VIN plate
Holes #8 original but unknown use.
Hole #9 Original. Is this for wiring from starter to Amp gauge and on to electrical system?
Hole #10 Looks original but no idea what it could be for.

Please let me know what these holes are for.

Also does anyone know where the original voltage regulator mounted? How is the wiring harness for the headlights and generator routed from the cab to the engine compartment?

Thanks for your help,
David

Re: 1937 Firewall hole I.D.
Bogart's Truck #1355435 Wed Apr 15 2020 11:21 PM
Joined: Jun 2011
Posts: 3,782
E
Shop Shark
There should be one for choke cable and hand throttle cable.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: 1937 Firewall hole I.D.
Bogart's Truck #1355440 Thu Apr 16 2020 12:02 AM
Joined: Jan 2018
Posts: 340
B
Shop Shark
Choke and hand throttle goes through the middle rubber grommet with 3 holes along with shield cable to the coil. I going what is on my 37 chev. Also if there was a heater that would have been the 2 3/4" holes on passenger side that look like they have been filled in.

Re: 1937 Firewall hole I.D.
Bogart's Truck #1355442 Thu Apr 16 2020 12:05 AM
Joined: Apr 2007
Posts: 805
L
Shop Shark
I will take a crack at this, however, be forewarned this is based on my '37 Chevy.
Ed, the choke, hand throttle, oil pressure line and water temp line go through the oblong grommet in the center which is held by the metal bracket.
Hole #1: I don't have these--it is not a GMC
Hole#2: One of the small ones is for a harness clip, placed inside. The others don't belong. Maybe you can tell which is original.
Hole#3: Yes, vacuum line to wipers.
Hole#4: I don't have that one at all.
Hole#5: For another harness clip, placed inside.
Hole#6: For the armored coil wire (Elektrolok). The smaller holes (6a) don't belong.
Hole#7: I don't have these.
Hole#8: I do have this, looks original, I don't know what it is for.
Hole#9: Yes.
Hole#10: I think that hole should be threaded and is one of the holes for the floorpan to be bolted to.

My truck did not have a voltage regulator, just a voltage cutout, which is mounted to the generator. The harness itself exits the cab forward to the horn and lights between the floor board where there is a sort of a cutout, and the cab just below your hole #5, and to the left in the picture from the driver side hood latch. If you look at your floorboard you will see what I mean.

The above observations are based on what little was left of the wiring on my truck, and examining another complete '37 Chevy. I hope this helps.

Kent

Last edited by Lightholder's Dad; Thu Apr 16 2020 12:13 AM.

1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix
Re: 1937 Firewall hole I.D.
Bogart's Truck #1355449 Thu Apr 16 2020 01:58 AM
Joined: Nov 2012
Posts: 140
B
Shop Shark
Great info. Thanks to all for the replies. I found a good picture on the net. https://photos.app.goo.gl/63XLCJkeAq1AcuG68

I agree with what Kent said except, I think both holes marked 6a are original as I see them on other vehicles. https://photos.app.goo.gl/1fRyZzMm4rxs2mNC8

My guess is the lower 6a and the hole #8 are for clips to secure the wire from starter to amp gauge. The upper 6a hole is still a mystery (to me).

Also, I don't think hole #10 is for the toe board/floor pan. The floor pan screws into a center cage nut but that's not hole #10. Hole #10 doesn't correspond to any hole on the floor pan so that one remains a mystery. Here's a better photo with a green arrow pointing to where the center cage nut is missing: https://photos.app.goo.gl/9rU1KRv4uouJt7Cv9

Thanks for the help. I ordered some cage nuts and in 12 hours holes #2 and #4 will be filled!

David

Re: 1937 Firewall hole I.D.
Bogart's Truck #1355461 Thu Apr 16 2020 03:11 AM
Joined: Mar 2004
Posts: 4,776
M
Shop Shark
The center oval grommet has the Choke, Throttle, Oil and Temp going through it...no electric. The oversize hole in the oval trim ring gets the Temp line so the bulb passes through.

Mike B smile

Re: 1937 Firewall hole I.D.
Bogart's Truck #1355462 Thu Apr 16 2020 03:16 AM
Joined: Apr 2007
Posts: 805
L
Shop Shark
David,
I went back to look at my truck. Regarding hole #10, you are correct. That does not correspond to where a cage nut is placed. I do not have that hole either and there is nothing I am aware that requires that hole. I recommend you fill that hole in 12 1/2 hours!

Regarding holes #8 and lower #6a you are correct again. In fact, I have a clip for the wire in lower #6. Upper #6 is present in my truck also, but nothing in it. I probably should put a clip in #8, the wire is right there (on the inside, of course).
This has helped me, thanks.
Regards,
Kent


1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix

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