bp71k5
3/4 ton status
It's the brake booster wire or the gas gauge lead. Forget which.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
'72 K5 - Greg's @MightAsWellK5 Build
- Thread starter Greg72
- Start date
This is the build description. I will improve this later. (GB)
It's weird....here's a shot I stole from Mike (1969 K5)
You can see the square hole for the fuseblock, and the smaller vertical rectangle hole for the parking brake and the two 3/8" holes to mount the parking brake bracket.
...but he doesn't have that extra hole there. I'm looking through the Factory Assembly Manual now to see if I can find an explanation. Speedo cable is up higher, the wiper washer grommet is inside the recessed hump area (up high) and I see an option to drill for a manual choke but that's much closer to the throttle arm (obviously).
EDIT: added photo from my original firewall just after tear down for reference...
-G
You can see the square hole for the fuseblock, and the smaller vertical rectangle hole for the parking brake and the two 3/8" holes to mount the parking brake bracket.
...but he doesn't have that extra hole there. I'm looking through the Factory Assembly Manual now to see if I can find an explanation. Speedo cable is up higher, the wiper washer grommet is inside the recessed hump area (up high) and I see an option to drill for a manual choke but that's much closer to the throttle arm (obviously).
EDIT: added photo from my original firewall just after tear down for reference...
-G
Last edited:
Not a first gen guy at all, but is it the hole for the mechanical oil pressure gauge?
I assume those years had the mechanical oil pressure gauge, my 73 had a mechanical one factory, but my 73 flatbed had idiot lights and no line coming in
I assume those years had the mechanical oil pressure gauge, my 73 had a mechanical one factory, but my 73 flatbed had idiot lights and no line coming in
bp71k5
3/4 ton status
Did 69 have power brakes? Maybe they didn't have a brake dummy light. At least that hole on mine is filled with a giant rubber grommet with a single wire coming through. I just don't remember which wire since I rewired the truck.
Mine is also a '72 and I've got the same hole. as near as I can tell, mine is how it came stock and it goes to the gas tank.
here is the wire coming through the firewall:
connecting to the top of the gas tank:
plugging into the fuse box:
hope that helps.
here is the wire coming through the firewall:
connecting to the top of the gas tank:
plugging into the fuse box:
hope that helps.
Thanks Ash! 
It's funny and sad..... When I first took this truck apart in January 2008, I figured that I would remember all of this stuff. "how long could it possibly take to fix this rust anyway?"
I begrudgingly took photos of the tear down, but not NEARLY enough of all the little details....
Let my struggle be a cautionary tale for future enthusiasts, especially if you have an unmolested "stock" vehicle. Take photos of every detail as you disassemble things..... My photos have been very helpful over the years for reference, and I don't think it's possible to have too many.
That hole is definitely for the fuel tank sender. It's interesting that the hole for this wire appears to be relocated from its position in 1969. Mike's firewall has extra holes up high that mine doesn't have at all. Now the decision becomes whether I want to keep all the wiring EXACTLY to the factory spec.
-G
It's funny and sad..... When I first took this truck apart in January 2008, I figured that I would remember all of this stuff. "how long could it possibly take to fix this rust anyway?"
I begrudgingly took photos of the tear down, but not NEARLY enough of all the little details....Let my struggle be a cautionary tale for future enthusiasts, especially if you have an unmolested "stock" vehicle. Take photos of every detail as you disassemble things..... My photos have been very helpful over the years for reference, and I don't think it's possible to have too many.
That hole is definitely for the fuel tank sender. It's interesting that the hole for this wire appears to be relocated from its position in 1969. Mike's firewall has extra holes up high that mine doesn't have at all. Now the decision becomes whether I want to keep all the wiring EXACTLY to the factory spec.
-G
bp71k5
3/4 ton status
I got my factory assembly manual out last night to check but couldn't get through it. Did you look there?
If you decide to not use the factory glass tube style fuseblock, my ATO fuseblock had space for extra wires to pass without needing the extra holes. I suspect most of them do.
If you decide to not use the factory glass tube style fuseblock, my ATO fuseblock had space for extra wires to pass without needing the extra holes. I suspect most of them do.
Now the decision becomes whether I want to keep all the wiring EXACTLY to the factory spec.
Because your truck is going to be to so close to stock
Actually it's this attention to detail that will make it a sleeper of sorts, with ridiculous Unimoggish ground clearance and those redone wheel wells that will make people go
Kinda like my '74 half-cab
I hope to confuse people at BlazerBash with that...-- A
Because your truck is going to be to so close to stock
-- A
Correct. It's a weird place to be.... I want to retain as many stock items as possible to keep the "look and feel" of the original truck, but obviously it will be different in MANY ways.
It's been a while, but I seem to recall that SOMEONE out there makes a 100% faithful reproduction of the orginal wiring harness and fuse block (right down to the glass BUSS-type fuses)... I think it was American Autowire but I'll have to search again.
I'm really tempted to go that way, but the engine compartment harness will probably be a total waste of money since I will end up wiring things very differently from stock (batteries in rear of truck, electric fan wiring, extra engine sensors, etc). I think this is one of those areas where I will have to do things "in the spirit" of the factory design, but incorporate the necessary extra bits to get the extra functionality I want. The fuel sender wire may simply end up bundled with a host of other "new" wiring and brought discreetly through the firewall somewhere.
I flipped through at least 100 pages of the FAIM yesterday and couldn't find a clear answer. Not surprising, that book is it's own kind of special torture!
-G
. Not surprising, that book is it's own kind of special torture!
-G
I sure am glad that you guys are going through this stuff on the firewall. I, like you, thought that I would remeber where it all went, as it was going to be a fast project.
Years later, I don't have a clue where all of the stuff goes.
So, feel free to steal as many pics of mine as you want. Dissect them, and hopefully tell me where everything goes in the long run.
Thanks,
Mike,
I noticed that your brake booster is missing both support rods.
There is a round one that comes off the top of the bracket (behind the booster) and another stamped one that comes off near the prop valve and anchors down low on the cowl. Lots of stress on the cowl where the brake assembly bolts up...it will be important to add those back in before too much longer to make sure you still have room.
-G
I noticed that your brake booster is missing both support rods.
There is a round one that comes off the top of the bracket (behind the booster) and another stamped one that comes off near the prop valve and anchors down low on the cowl. Lots of stress on the cowl where the brake assembly bolts up...it will be important to add those back in before too much longer to make sure you still have room.
-G
Thanks, I went back a couple of pages and seen what you were talking about on yours. I guess I need to try and find those.
Are you going back with the same size booster, one like AJ's or the hydro? I still don't know what I'm doing, just wanted to make sure that there was going to be enough room for something with the tubes.
Are you going back with the same size booster, one like AJ's or the hydro? I still don't know what I'm doing, just wanted to make sure that there was going to be enough room for something with the tubes.
I'm not sure yet. My disc brakes are off a Ford SuperDuty, so I'll need to research what sort of booster size and piston was used in that application. If I don't create the correct amount of line pressure for the application, the brakes will never work right. Even with perfect brakes it's going to be hard to hold the truck back when it's in superlow range, especially with a BBC that makes peak TQ just off idle.
-G
-G
Why would you try to use original wiring? You've gone this far into thr build so making your own harness should be no big deal for you. I went with the EZ Wiring 21 circuit universal harness and its the best mod I've done. Are you going to run efi?
Mostly for ease of troubleshooting later on.... factory wiring will match all the orignal factory wiring schematics and that may prove to be a lifesaver later on if I ever have to deal with an electrical gremlin. Plus, there is an awful lot of wiring behind the dash that will remain unchanged (turn signals, headlights, gauges, ignition, backlighting, HVAC, etc) I'm not sure I want to swap all of that out....
Who knows? Maybe when that time comes I will build something from scratch. I already bought several hundred $$$ worth of factory-style wire colors (solids, striped combos) If I can locate EVERY color, combinantion and wire gauge that was in the factory harness then I suppose I could lay it all out the way I wanted and still be able to refer to the factory schematics later on if needed.
EFI is definitely part of the plan. I was going to do the Holley Dominator EFI since the controller does both the fuel injection maps as well as providing a fully programmable set of maps for the 4L80E. The integration of all the relevant sensors to control both the engine and transmission seems really nice.
-G
Who knows? Maybe when that time comes I will build something from scratch. I already bought several hundred $$$ worth of factory-style wire colors (solids, striped combos) If I can locate EVERY color, combinantion and wire gauge that was in the factory harness then I suppose I could lay it all out the way I wanted and still be able to refer to the factory schematics later on if needed.
EFI is definitely part of the plan. I was going to do the Holley Dominator EFI since the controller does both the fuel injection maps as well as providing a fully programmable set of maps for the 4L80E. The integration of all the relevant sensors to control both the engine and transmission seems really nice.
-G
for what it's worth, I have both of those support rods still, but can't use them with the hydroboost (gotta fab up something new). if anyone needs them I'm sure they'd fit on a flat rate box...
bp71k5
3/4 ton status
I'm pretty sure it's AAW as well that makes the glass fuse block. The painless block I used had all the factory colors and connectors as well, except for the "extra" stuff it had was different colors.
Think about how the factory added extra accessories like AC, interior lights back then. They used those splitter connections near the fuse block that make it all these extra bundles of wire. Once you add EFI, winches, radios, any other electronic gizmos, you'll need to add some additional fuses somewhere. ATO fuses are smaller and so they are able to fit more of them in the same space.
I drew out my own wiring diagram in CAD for when I need to do any troubleshooting.
BUDDY
1/2 ton status
American Autowire is the place. http://shop.americanautowire.com/72chevrolettruckdashharness1.aspx
You could piece together what you wanted/needed to use.
http://shop.americanautowire.com/search.aspx?find=72+chevrolet+truck&log=false&category=964
They are absolutely the best quality harnesses that are made. No question in my mind there. I don't have empirical data to support that, but I have installed a full harness on my old blazer & used one of their kits. It was a pain, but not because of the harness.
All that being said, I'd recommend a custom harness for what your are wanting to do. You have too much customization in your body & frame to use a "factory fit" harness. Not to mention the EFI, & all the other "doodads" & "hee-haws" you will no doubt have incorporated into your build by the time it's all wrapped up. (Please note that I didn't say "done", this build will live on as long as Greg lives on.)
I loved the harness I finally put in, but I would definitely recommend keeping the old harness un-cut. THAT is what caused me the most pain during the install I did.
Might I recommend -
http://shop.americanautowire.com/highway22panelwiringkit.aspx
It'll just about cover you completely.
Just some thoughts.
Later,
Buddy
You could piece together what you wanted/needed to use.
http://shop.americanautowire.com/search.aspx?find=72+chevrolet+truck&log=false&category=964
They are absolutely the best quality harnesses that are made. No question in my mind there. I don't have empirical data to support that, but I have installed a full harness on my old blazer & used one of their kits. It was a pain, but not because of the harness.
All that being said, I'd recommend a custom harness for what your are wanting to do. You have too much customization in your body & frame to use a "factory fit" harness. Not to mention the EFI, & all the other "doodads" & "hee-haws" you will no doubt have incorporated into your build by the time it's all wrapped up. (Please note that I didn't say "done", this build will live on as long as Greg lives on.)
I loved the harness I finally put in, but I would definitely recommend keeping the old harness un-cut. THAT is what caused me the most pain during the install I did.
Might I recommend -
http://shop.americanautowire.com/highway22panelwiringkit.aspx
It'll just about cover you completely.
Just some thoughts.
Later,
Buddy
Buddy,
Thanks for that... I couldn't find the images on the AAW catalog I downloaded.
There's still time to figure out a wiring strategy. I think I need to map out EXACTLY what extras I plan to add to the truck and then work backwards to build a harness to support it. Maybe a factory harness for the majority of "stock" items, then a small aftermarket fuse block for the stuff like EFI, offroad lights, stereo, etc?
Anyway..... It's a cold, icy day here in New England. Seems like a good day to fire up the wall heater in the manspace and put a bit more structure on the engine cradle?
-G
Thanks for that... I couldn't find the images on the AAW catalog I downloaded.
There's still time to figure out a wiring strategy. I think I need to map out EXACTLY what extras I plan to add to the truck and then work backwards to build a harness to support it. Maybe a factory harness for the majority of "stock" items, then a small aftermarket fuse block for the stuff like EFI, offroad lights, stereo, etc?
Anyway..... It's a cold, icy day here in New England. Seems like a good day to fire up the wall heater in the manspace and put a bit more structure on the engine cradle?
-G
Buddy,
Thanks for that... I couldn't find the images on the AAW catalog I downloaded.
There's still time to figure out a wiring strategy. I think I need to map out EXACTLY what extras I plan to add to the truck and then work backwards to build a harness to support it. Maybe a factory harness for the majority of "stock" items, then a small aftermarket fuse block for the stuff like EFI, offroad lights, stereo, etc?
Anyway..... It's a cold, icy day here in New England. Seems like a good day to fire up the wall heater in the manspace and put a bit more structure on the engine cradle?
-G
If it were me doing the wiring I would install whatever your brand of basic vehicle harness you wanted. Then install a separate system for the added items. After dealing with some fuse and wiring things I would use circuit breakers over fuses with the switch next to it. THink offroad race truck style wiring.
