'70 & '71 HD Instrument Panel Wiring Diagram

[martincom]

Does any one have a service manual that they can scan the optional wiring diagram for the HD instrument cluster? I'm seeking to add a tachometer feed to the cab, within my '71 D100. I'd like to utilize the same color of wires and the same bulkhead connector terminal location. We're between homes and all my manuals are packed and stored in the front of a '53 semi-trailer that is loaded floor to ceiling, front to rear.

[Wildergarten]

Does any one have a service manual that they can scan the optional wiring diagram for the HD instrument cluster? I'm seeking to add a tachometer feed to the cab, within my '71 D100. I'd like to utilize the same color of wires and the same bulkhead connector terminal location. We're between homes and all my manuals are packed and stored in the front of a '53 semi-trailer that is loaded floor to ceiling, front to rear.

Sounds like quite the move. I've been looking at fitting a similar set of Stewart Warner instruments in mine, but fitting a vacuum gauge in that space is just too tight.

[martincom]

I've been looking at fitting a similar set of Stewart Warner instruments in mine, but fitting a vacuum gauge in that space is just too tight.

Possibly a combination gauge, where they pair a set of meter movements into the same housing? That would free up an opening.

They taxed us out of MN. We sold our lakehome in February. My bride still has a few months before she can retire. So we rented half a duplex for a year. We've been actively searching for a lakehome in AL. Not to many check all the required boxes and the couple that had sold before I could drive there to view them. The rising interest rates and inflation is curbing the demand and with that, price. So the delay is likely working to our benefit. It'll come in God's timing.

[Wildergarten]

Possibly a combination gauge, where they pair a set of meter movements into the same housing? That would free up an opening.

The best I could do with the vacuum gauge is about a 3/16 gap between bezels. The sketch shows two schema. Both leave room for a couple of switches, one for the voltmeter to switch between batteries as a diagnostic when isolated. Lots of room for indicator lights, which I may need as a way to remind me that I've left something on in the back. If I can find a good ribbon cable for running the relays, it might afford that.

[soopernaut]

I've been looking at fitting a similar set of Stewart Warner instruments in mine, but fitting a vacuum gauge in that space is just too tight.

Not to distract from the original post here, but since it was brought up, if you had a 69-71 dash/gauge cluster you could fit 8 gauges in it. I have one from a bus that has 7 or 8 gauges, including a vacuum gauge.

[Wildergarten]

Not to distract from the original post here, but since it was brought up, if you had a 69-71 dash/gauge cluster you could fit 8 gauges in it. I have one from a bus that has 7 or 8 gauges, including a vacuum gauge.

Got a photo? I got 7 into the sketch with 3/16" spacing. Any closer than that and it would be hard to clean. In no case are my sketches addressing the hold-down brackets from the back, but I doubt they would be a problem. With this layout, it has an spst switch for checking the condition of the two batteries with room for one more, not that it is an issue with regard to the rest of the dash. I just added one for an electric fuel pump to prime the carb float level before starting.

Do you have a diagram for the stock vapor recovery system, or is there a better one that is more widely available? It's one of the few smog provisions of which I actually approve.

[PwrWgnDrvr]

69-71 HD cluster is way different than pre 69 and won't fit the earlier dash.
Sorry your thread got hijacked Martin.
Anybody have a wiring diagram they can post for the 70-71 HD cluster?

[martincom]

Not a problem on hi-jack. I found it rather interesting. It'd be nice to have that HD instrument cluster.

I believe a fellow on FB Sweptline.org group is going to take care of me.

[soopernaut]

Got a photo?

Not mine, but you get the idea... It will not fit an early dash, but with all the mods you plan for the truck perhaps a dash swap isn't out of the question. I don't recall the year of truck you are building, but it seemed you had at least one truck that was a 69 or later.

[Wildergarten]

.

[Wildergarten]

I don't recall the year of truck you are building, but it seemed you had at least one truck that was a 69 or later.

(Need more coffee.) "Had" is the operant term. I'm building a '68. The '69 cab is gone (I'm wishing I'd kept the windshield wiper sheetmetal too). But your image suggests options I'll take a harder look at. Time for more doodling.

[Wildergarten]

It will not fit an early dash, but with all the mods you plan for the truck perhaps a dash swap isn't out of the question.

I got a bit more serious with the layout re the constraints placed by the original panel design. It is (of course) more complex than it first appears. There was a lot of attention to artistic detail on Dodge's part in the design. The top and bottom radii are different as are the top and bottom corners, nor are the end edges parallel. It is interesting how they dished the plate to hold the glass tighter with fewer stress concentrations and to prevent vibrations.

If one is willing to blow off the top attachment hole and consider adding two tabs to the dash proper for attachment screws on the top edge (not shown in the sketch), it gets a lot easier to make a pleasing seven hole pattern (the lower rendition below). Thanks to martincom for an amusing exercise but I'm more likely to stick with the six-hole dash with my truck. If I was going to install a 4bbl Holley for a carb, I'd be inclined to try squishing in the seven gauges, as getting the vacuum settings for the correct power valve and vacuum secondary springs and jetting dialed in is virtually impossible without a vacuum gauge. Had an oak panel dash pattern like this in my old Dart and it was a pleasure. That carb had ports in the top of the float bowls with angled adaptors for the main jets so that one could use a special driver to change jets without removing the float bowls! It was pretty slick.

[martincom]

I didn't see the A/F gauge. Where are you putting that?

[Wildergarten]

I didn't see the A/F gauge. Where are you putting that?

I've never used one (did they have those in the 80s?). It's been since the early 90s I've spent much time turning a wrench other than brake jobs and such. The last car I had with any serious power was that Dart that died in 1987.

[martincom]

They're somewhat recent. They consist of an O2 sensor in the exhaust pipe, near identical to the modern fuel injection vehicles. They take the trial-n-error, guess work out of jetting a carburetor. Rather than having to stop, remove spark plugs, and "read" them; it'll provide a real time indication of your O2 ratio in the exhaust.

Once you have it set, you really don't need it. I was poking fun at you. Folks that race typically have the permanent, in-dash, version as they are forever changing things that would impact it.

After a couple of years of procrastinating over the cost, I just sprung for the "portable" version ($500) and the optional stainless sleeve/longer cable, for the O2 sensor, that slips over the tail pipe ($200).

I'm finally going to optimize my initial timing, total timing, advance curves, main jets & power valve. I'll see where I end up at that point to determine if I need to do anything with the secondary and the accelerator pump. Just from a drive-ability and exhaust gas smell standpoint, I know I'm close, but it could be better.

I'm getting 13mpg and pretty sure I can make that significantly better. The crazy cost of gasoline helped tipped the scale to pop for the A/F meter. At best, I only put 2500 miles a year on the D100, but at the crazy price of fuel, I'm thinking I'll pay for the A/F meter in less than four years. Besides, my muscle cars could likely be better, as well.

https://www.fuelairspark.com/air-fuel-tuning.html

[Wildergarten]

I was poking fun at you. Folks that race typically have the permanent, in-dash, version as they are forever changing things that would impact it.

Suspected as much, but I do a good straight man if need be. It keeps me from getting snarky.

I'm getting 13mpg and pretty sure I can make that significantly better.

With a big block? In either case, that is excellent! I'm expecting about 5-7 on our property, but then I seldom break much more than walking speed. This place is really steep and the loads are usually either big or generally unstable or involving small trailers full of wood or a splitter. Longer trips are for bulk materials such as rock. MPG is not a consideration and a 2bbl is all I want or need. Any demand for more power is asking to spin tires on dirt, which is (frankly) dangerous here no matter what the direction. There's no room for getting going.

Besides, my muscle cars could likely be better, as well.

Just knew that would be there. There is no point in having a muscle car without that sound of the secondary induction opening up pulling through the revs. There's nothing like it. My old Dart did 105 in third gear. If I managed to sucker a 911S into a freeway race on SR24, I'd drop it into second at 70 and wait for them to disappear in the rear view mirror. An SC was a push and a Turbo Carerra could take me (if he could drive). But hey, the car was a 270 wagon, so it was insulting in any case. Everybody who knew loved that car.

It was a gas, but never again. My responsibilities give me more reason to live. If one doesn't drive that way every day, it's foolish to try.

[martincom]

With a big block? In either case,

No, 318, in my '71 D100. It's my daily driver in the summer. I rarely ever carry anything in the box. I do pull trailers with it, sometimes near 7k. It is pretty much a passenger car drivetrain: automatic transmission, 8.75 w/3:23 gears.

A previous owner had removed the Carter 2 barrel, intake, etc and replaced it with a Carter AVS from a non-HP '71 440. It was just too much carburetor for that engine, poor throttle response, poor idle, hesitation coming off idle, and a rich exhaust that would make your eyes water. I would have much preferred the original Carter 2 barrel, but that change was three owners ago and he had passed away.

Back in the day, 318s with Carter 2 barrels were a dime a dozen. That is not the case any longer. I researched pulling all those required parts together to switch back, but it added up to quite a bit. So I opted to replace the AVS with the smallest Holley 4 barrel I could get, a 390 cfm 4160. I also ordered the throttle cable bracket for a 340, so I could correct the throttle linkage geometry and achieve wide open throttle. I bolted it on out of the box and it made a world of difference without any adjustments. All I've done thus far is set the float levels, idle mixture and idle speed.

[Wildergarten]

So I opted to replace the AVS with the smallest Holley 4 barrel I could get, a 390 cfm 4160.

Interesting choice; I didn't know they went that small. Back in the day, I had a factory single plane manifold for the Holly I ran.

I HATE that transfer tube with the side-hung float bowls. It makes playing with jets a total pain. Good thing you didn't have to mess with it.

[nutz]

13.5 is what i get with my 12 ram 1500 hemi and i never see the highway
seems like you can do better my supercharged 400sb suburban got 14mpg highway
carb may be too small and you might be getting into the 4bbl to much or
323 might be a little to high for getting rolling lots of varibles when it comes to max mpg
what type a/f sensor are you using $500 sounds like a deal for a tail pipe emissions tester
would like to add one to the tool box

[martincom]

what type a/f sensor are you using $500 sounds like a deal for a tail pipe emissions tester
would like to add one to the tool box

I posted a manufacturer's link, for the A/F meter, in one of my posts, above. The FAST brand. The $500 didn't include the tailpipe components. The $500 was the dual sensor unit and it comes with a pair of O2 sensor threaded bungs to weld into the exhaust pipe, just like the O2 sensors for the microprocessor based fuel injection of today's vehicles. The tailpipe sensor sleeve was another $90 and the longer cable was another $100. I could have fabricated the cable, but by the time I sourced the connectors and the minimum order quantities, shipping, etc; I was going to be at the $100.

I would have went with the weld in bungs, but the exhaust system is a previous owner/muffler shop special that is the typical patch job. They left the Y pipe, sawed it off and made a pipe from it to the muffler. The tail pipe appears to be a light gauge parts store supplied unit, as it already is starting to rust through. The Y-pipe is not too sweet, either. So at some point in the not too distance future, it'll need an exhaust system. At that time, I'll go with a stainless system from Waldron's. I'll have them add stainless bungs for the O2 sensors when they fabricate it.