1971 D100 questions

[WisD100]

Hi Guys--

I hope that the experts on this forum can help me with several questions I have about my '71 D100.

Here they are:

-- One of my sun visors doesn't pivot, is there a repair- how do you take them apart?

-- Does a '71 225 have hardened valve seats and are the valve guides compatible with modern no-lead fuels? Do most people running 225s use lead substitute?

-- Does anyone know how short/wide Sweptline gas tanks differ between '69 and '71? I see that there are several fuel sending units available but most say they fit up to '69 tanks but not '70-'71 tanks, I don't get it! And, there are contradictions between venders, one vender says the a XZY (TSU6) unit will fit while others say it won't. Can anyone clear up the fit/won't fit question?

-- I'd like to put a manual choke on my truck. Can someone post a photo of the choke mounting hardware and where I can buy one?

These questions might be the tip of the iceberg!

Thanks!

[martincom]

- One of my sun visors doesn't pivot, is there a repair- how do you take them apart?

The visor will pull off the shaft. The driver's side on my '71 will not stay up. It creeps down with mild road vibration. I've tried a number of things to tighten it up: wrapping the shaft with tape, adding a length of mechanic's wire along the shaft, etc. Like you, I'm probably battling age whereas the material has become hard has no pliability or elasticity. I see the vendor easy (skip a word) street has them back in stock. I'm waiting for one more item to be back in-stock and I'll order a pair.

-- Does a '71 225 have hardened valve seats and are the valve guides compatible with modern no-lead fuels? Do most people running 225s use lead substitute?

I have no slant six knowledge. I'll defer to others.

-- Does anyone know how short/wide Sweptline gas tanks differ between '69 and '71? I see that there are several fuel sending units available but most say they fit up to '69 tanks but not '70-'71 tanks, I don't get it! And, there are contradictions between venders, one vender says the a XZY (TSU6) unit will fit while others say it won't. Can anyone clear up the fit/won't fit question?

The older sending units fit and work fine. The big (only?) difference is the direction the fuel outlet nipple points. I purchased a repro unit from an eBay seller and installed it in my '71. The OEM unit's outlet nipple points to the right. The eBay seller's unit pointed to the left. I just utilized a longer piece of fuel hose to connect it, making a small loop in the hose to reverse the orientation.

I'm gathering the change came with the vapor recovery system that was added for emission requirements. Rather than venting through the cap, the vent line runs to a fuel/vapor separator mounted in the upper right rear cab pillar. The separated vapor exits and is routed by another line to the crankcase breather. Here, it is drawn back into the combustion chamber, via the PCV system, to be burned. The gasoline that condenses, in the vapor separator, drains back into the tank.

An internal baffle was added to the top of the tank to create an air cavity to allow for fuel expansion. I'm gathering in prior years, the sending unit was mounted in the center of the tank, rather than on right side, as it is in our '71s. The addition of this baffle would explain why it was re-located to the right side and perhaps why the orientation of the outlet nipple was changed.

-- I'd like to put a manual choke on my truck. Can someone post a photo of the choke mounting hardware and where I can buy one?

I'm gathering some of the larger trucks may have come equipped with a manual choke, as that is what one of the capped of dash mounting holes is for. I have found that automatic chokes, when adjusted correctly (according to the factory service manual), work well. Attempting to convert to a manual choke will likely result in a Rude Goldberg cobbled cable mounting and connection to the choke butterfly. I'd suggest your money would be better spent correcting any deficiencies in the automatic choke.

[PwrWgnDrvr]

70/71 have larger tanks and the sender is longer (taller for depth) than earlier tanks.
Manual choke uses the cable plus a special spring loaded mount/termination bracket on the carb for proper function. I have a couple trucks with them and they are very difficult to find/acquire. Without that bracket, it will be mickey mouse like Martin said.

[dodgeboykim]

71 SL 6 Engines do not have hardened seats for unleaded gas.

[712edf]

Medium duty trucks kept manual chokes until their last year of domestic production, 1977. Also some of them had a throttle control. This is one of the handiest options ever put on a truck.

Bucky

[WisD100]

Guys--

Thanks for all of the tips and information! I've found most of the same information as your replies mentioned and will take the advice about the manual choke.

Just a little information about my D100. I've owned it since 1983. It came stock with a 198 ci engine which I replaced at that time with a rebuilt 225 ci. The rebuild included a Crane cam, Clifford headers and porting. After a couple of decades without use I'm putting it back on the road again. One modification that may interest other D100 owners is the Feather Lite aluminum case A833 transmission with overdrive fourth gear that I installed. It really cruses the freeways!

--WisD100

[martincom]

70/71 have larger tanks and the sender is longer (taller for depth) than earlier tanks.

I had compared the eBay repro sending unit with the original. They matched up on length of pickup tube and the length/arc of the float arm. Other than the the direction the outlet nipple pointed, the only other difference was there was an offset bend in the bottom of the pickup tube and it had a strainer cartridge on the end of the tube.

The OEM sending unit, or what I'm presuming was the OEM unit, did not have the offset bend nor the strainer cartridge. I had previously attempted to add a strainer cartridge to the OEM unit, but with it in place, it could not be fed through the sending unit opening of the tank. With the offset bend in the eBay repro, it would fit through the sending unit opening with the strainer installed.

With the addition of the expansion baffle in the evaporative control fuel tanks, I was wondering if that was going to reduce rated capacity. With how the tank mounts, I don't see how its volume could be increased by height, as the mounting bolt locations did not change. Thus I would speculate the fuel level sending units pickup depth and float arm length/arc would be the same. Possibly the overall length or width increased? I've never had two side by side to compare....and I haven't ran the truck out of fuel to find out the hard way what the actual capacity is.

[PwrWgnDrvr]

Martin, the problem you are having is using ebay as the comparable.
I went out to my sheds where I have a basket with a dozen senders in it and a stack of a dozen tanks.
The later tanks are 2" taller and several inches longer. The later sender is also 2" taller, with both a longer vertical drop from the top of the tank and a longer section after the bend. That lower section is straight on the later senders and has a dog leg on the early senders. The float arm is also longer since it has a longer vertical distance to travel from full to empty.
Early tanks were 16 and 18 gal capacity. Later tanks were 23 and camper specials could have a 25 gal. 23 gal were the most common, which is what my 70 W200 has, verified by running it empty in a gas station, pushing the truck to the pump and filling it.
I don't currently have a way to take a pic and reduce it for posting, or I would.

[martincom]

PwrWgnDrvr, thank you for clearing up the mystery. I would agree any repro parts from ebay/China are a crapshoot. However, when it is all you can source, you're stuck.

Now, you have me wondering if what I presumed was the OEM sender was actually the OEM sender. I did save it and I took some photos/measurements of it. Can you tell me what year and tank size this would be for? My truck is at the body shop having some paint runs in the inner roof panel addressed. When I get it back, I'll make some measurements of the tank and pull the sending unit and measure the tank depth from the face of the sending unit opening.

Float Arm Length

Pickup Tube Length

Pickup Tube Tank Depth: 16 inches

[WisD100]

Martincom--

I've owned my '71 D100 since 1983. I'm darn near positive that my pick-up is original equipment. It's length from the top or the unit to the bend is 6.5" and from the bend to end is 12.5". I think that you have the original fuel pick-up for '71 23 gallon tanks.

--WisD100

PS: You have a PM.

[JohnB]

Martin, the problem you are having is using ebay as the comparable.
I went out to my sheds where I have a basket with a dozen senders in it and a stack of a dozen tanks.
The later tanks are 2" taller and several inches longer. The later sender is also 2" taller, with both a longer vertical drop from the top of the tank and a longer section after the bend. That lower section is straight on the later senders and has a dog leg on the early senders. The float arm is also longer since it has a longer vertical distance to travel from full to empty.
Early tanks were 16 and 18 gal capacity. Later tanks were 23 and camper specials could have a 25 gal. 23 gal were the most common, which is what my 70 W200 has, verified by running it empty in a gas station, pushing the truck to the pump and filling it.
I don't currently have a way to take a pic and reduce it for posting, or I would.

Terry,
The 70 trucks came with a 25 gallon tank. This was for all models D/W 100-300. The exception was a 23 gallon tank in California trucks. I am reading this off of the 1970 Dodge truck dealer brochure that came with my truck when it was ordered new. Wouldn't 1971 have been the same? I know you said you measured yours from empty and it's 23 gallons. Since you are in California, is your truck an original Ca truck?

[PwrWgnDrvr]

John, it probably was set up for CA. I bought it at GSA auction in 78. It was a USFS truck that spent all its time in CA.....so, US Gov't truck in CA.

Martin, sorry I forgot to answer your question, but yes, it looks exactly like a 70/71 sender.
Senders are probably the same for 23/25 gal tanks as the difference could only be in length, not depth.

[PwrWgnDrvr]

To further differentiate, I just went out and measured 2 cabs. In the 61-69 cabs, the tank mounting bolts are 15.5" above the step where the tank sits. On the 70/71 cabs, the bolt holes are 17" above. That confirms the later cabs are made to accommodate the later tanks that are both longer and taller.

[WisD100]

PwrWgnDrvr--

Thanks for the clarification on tank size and cab modification. I believe my truck was a BLM truck, it was originally light blue. I lived in Oregon at the time and it was generally understood the the light blue truck were ex-BLM. It is also a California truck with the pollution control tank venting and the expansion tank feature.

--WisD100

[martincom]

JohnB,

My '71 D100 was a CA truck and has the vapor separator in the upper right pillar. I'm gathering only CA trucks had that in '70 & '71. According to the FSM, the vapor system trucks also had a baffle added to the fuel tank interior, to allow for fuel expansion with temperature. That would be logical, as without it, the fuel would expand into the vapor separator and from there into the oil pan, if the truck had been parked out in the hot sun after being filled, for example. Here, in MN, the ground temp is about 45F near year around. So that is what the gasoline temp would be when filled at a service station w/underground tanks--the norm here. In July, afternoon temps can top 100F. So some serious expansion will occur.

I'm going to speculate the tank outer shell is identical between 25 and 23 gallon tanks. The difference being the baffle reducing the capacity to 23 gallons on CA trucks. I had the sending unit out of mine, immediately after filling the tank. The fuel level was about three inches below the top of the tank, if memory serves me correctly. I would expect that much with baffle equipped tanks.

[JohnB]

Martincom,
Your reasoning on the baffles and tank dimensions makes sense to me since 23 gallon tanks were only specified for California trucks. Terry originally mentioned that he thought the sending units for the tanks were the same because the only dimension change was in length. We need to measure from the inside of the cab to the edge of the tank on both sides of 23 and 25 gallon to be sure they are the same length externally. I have a parts book so I will look into the sending units to see if they are different numbers. I know the part # for the 25 gallon is 3420883. They are really scarce; I have only seen 2 NOS come up on the auction site in the last several years. Mine works well enough when full but when it indicates empty I can only pump about 17 gallons into the tank {so it's not empty}. Something is wrong with the "rheostat" or whatever its called. I have had it out and looked it over but haven't nailed down the problem yet. I am 100% positive it's the original tank and the truck was ordered in Florida when new so its a 25.

[PwrWgnDrvr]

John, are you sure you have the correct sender? If it reads empty before its all the way to the bottom, bend the float arm to be lower when it hits that point.

[JohnB]

Terry,
I'm almost positive its correct. I know the truck well and knew the original owner. I'm the 2nd owner. The truck is about as factory original as any I have seen. Truck was always garaged since new, serviced by him exclusively and so on. He kept a ledger book of every time he did anything at all to the truck and he would have written if the sender had been changed. He was quite a character...chief air flight mechanic on a Korean war aircraft carrier. Those guys were meticulous in their work and documentation. The sender reads correctly when full so wouldn't bending the arm down cause the sender to read full before it actually was full? From what I understand, the rheostat changes voltage or resistance when the float moves the arm up and down. This is what gives the gas gauge reading. I need to take it out again and closely look at everything and put a meter on it to measure it when moving the arm. Only information I could find online says that a Dodge sending unit should read 73ohms when empty and 10 ohms when full.

[PwrWgnDrvr]

Doesn't matter if it reads full when its not. You know its full when you fill it to the top of the fill pipe. Empty is what matters cuz that's what strands you on the road.

[JohnB]

Doesn't matter if it reads full when its not. You know its full when you fill it to the top of the fill pipe. Empty is what matters cuz that's what strands you on the road.

You had to go make sense of this just when I thought I had another project I'll take it out and measure the ohms anyway out of curiosity. I also want to make sure when I reinstalled it last time that I didn't put it in off center and cause the float to hit the tank when the fuel level goes down.