What do these vacuum lines do? Related to my troubles?

[1962m37]

Hi,

When I bought my M37 the line closer to the camera was disconnected (broken fitting). The truck had been running fine without it. Recently, it sputters and hesitates when driving. I can shift through the gears, but it really hesitates bad and there's no power. You can eventually climb in speed, but it takes a while. With my very limited knowledge it felt like a fuel delivery issues. I saw an inline fuel filter outside the tank was full of rust so assumed that was the problem. I changed the filter twice and tonight my friend and I took apart the carb and cleaned it - it was filthy, but after re-assembly same problem. Now, I'm having a hard time re-connecting the second vacuum line (farthest from the camera). Can someone tell me what they do and is it necessary they are hooked up? This is between the carb and air filter. Figured I'd start here as I try to troubleshoot the hesitation. Thank you.

[Cal_Gary]

Can't tell for sure by the picture but they are likely the fuel tank vent lines, or one that goes to your military distributor to help cool it.
Gary

[NAM VET]

they are vent lines, one from the fuel tank, the other from something else I can't remember. there are short rubber lines from hard lines coming from the rear alongside the driver's inside frame rail. Since I made up my own fuel and vent lines, it was too hard to make them the praise length to attach the short rubber lines. So I made my new vent lines with flared ends, and used short fuel injection rated
rubber hoses with clamps to attach to these. A hot coil can cause hard running, and be sure your fuel cap is set to vent inside the lid. Also, vapor lock can cause you to have no fuel pressure. I finally put a fuel pressure gage on my Facet fuel pressure line. with an adjustable regulator and could then see vapor lock, which I fixed wire insulation, and could make sure my fuel pressure was not too strong or too week. I have lots of pics of my truck's rebuild, if you need any views. NV
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[NAM VET]

a global view; NV[url=https://postimages.org/][img]https ... .jpg[/img][/url]

[NAM VET]

being more specific for the vent lines, I rented a quality flare tool, and put a new threaded flare/nut on one end of about a foot long piece of new hard line, and a simple flare on the other end, then when my engine was back in, cut some fuel injection line to the right length, and had put a flare on the end of the long hard line, and one on the end of my new short hard line, the one with the new metal flare/nut, and used hose clamps to connect them. They are not pressurized, so not a problem. Let me know of you wish other pics of this or any other linkage or connection or part . NV

[PoW]

The distributor venting is critical, as it carries off the small amounts of corrosive gases produced by the arcing of the points. They terminate inside the air horn with tiny 90 degree elbows inside it. One faces the air flow, the other goes the opposite way. A small amount of cooling is also provided by this system, and if any condensation occurs inside the distributor it is also removed.

The fuel tank and master cylinder also have vent lines (with the little rubber hoses), essentially to provide dry air makeup for fluid displacement whilst fording.

PoW

[Elwood]

From the first photo, it appears you have the fording enclosure installed on the air cleaner? If so, you might consider removing it unless you're actually fording with the truck. That enclosure cuts down on air flow into the engine, and thus reduces engine power.

To reiterate what others have posted, if you're running the military waterproof (i.e. enclosed) ignitor, the vent lines for it are necessary.

[outpostm37]

I upgraded to the Pertronix to eliminate the points. EZ upgrade and no possible issues with ionized gasses in the distributor causing problems.

[Cal_Gary]

Nice photo Outpost! I want to go with the Pertronix too once I get the correct number off my civvy distributor.
Gary

[outpostm37]

Once I upgraded to the Pertronix and an electric 24 volt aerospace fuel pump, ZERO issues while driving in the Arizona summer heat.