47-55.1 Confirm tank mockup

[51 3600]

Finally got Tanks Inc. tank delivered and am working on mocking up it's position in my '51 3600. I don't have the bed close by nor do I have any of the wood blocks so I'm going by some measurements I've taken, info from vendors and what I can find on here and the web. Would like some feedback from you folks to see if my thinking and assumptions are correct.

Pic below is drivers side view of frame with blocks representing bed parts. Yellow is cross sill/slat/support(?) at rear where bolt attaches bed to frame. Using 2.25" for height. Red is wood block between frame and cross sill, also 2.25' high. Green is bed bottom. So I figure I have about 4.5" of space to bring the filler tube from the tank, under the bed, out through the bed side and up into the fender for a fender mounted filler neck.



I'd like the tank as far forward as possible. In this configuration there are about 7" horizontally between the axle and the tank (looking straight down from above). Hoping that is enough for the exhaust pipe to go up, over and down behind the axle then out the back.



Top of tank to be 1" above frame rails.



That leaves about 2.25" of the tank hanging below the frame and about 11" from the back of the tank to the end of the frame rails. Hope that is enough room for repositioning rear crossmember and bumper brackets.

Comments, suggestions, corrections, ruler hand-slap appreciated. Thanks all.

[fauXGT]

This is what I did for the 51-CGX tank in my 51 3100 frame.
I took into consideration that the frame was tweeked a bit in the back, so the extra rear structure helped.
And also wanted a bit more protection from a rear collision, but I wanted the exhaust clearance over top of the C-4 rear to the sides of the tank. Hope this helps.

[dsraven]

i get it that you want the tank as far forward as possible but ensure you leave room for the hot parts and maybe some heat shield around the tank. possibly grab an old tailpipe from a wreck, which should have a normal over-axle bend, and see if it will fit with adequate room. some fellas have also ran the exhaust on the outside of the frame so it misses the tank area, just a thought. personally i am not a fan of the pre-axle exhaust dump, either out the side or under the truck, because there is a lot of bad corrosive stuff in exhaust so why dump that down the side of your truck or under it. not to mention the heat and carbon monoxide that can be drawn into the cab if dumped under the truck. just me though, others have their own thoughts on that. perfectly fine.

[mr48chev]

That will work fine and I think you have as much exaust pipe clearance as a lot of oem cars with the tank in that spot.

I always forget that that next to the back cross sill is right where a guy thinks he can raise the tank up higher.

[51 3600]

Thanks all for the input, very helpful. FauXGT the last pic you posted is exactly the position I’ve figured for my tank. That pic Helps a lot. What did you use to transition from what looks like 2” filler hose to the stock filler neck which is 1.375”?

‘Nother question. Since the in-tank fuel pump I’m using has a vent, can I eliminate or at least block off the vent tube on the stock filler neck?

[dsraven]

I would say you may want to keep the filler vent tube, it will help with filling the tank. the vent in the fuel tank will likely not allow enough venting for when the tank gets filled. imagine the flow from the filler nozzle and then try to imagine that much air being displaced through the tiny vent the fuel pump will have. I suppose another way to vent the tank for filling would be to snake a vent line up inside the filler piping but that seems counter productive since there is already a good sized vent tube built into the filler, you just need to connect it up.

[mr48chev]

I have to agree 100 % with dsraven, keep the filler neck vent tube even if you have to modify it a bit.

That is what lets the air out of the tank when the gas goes in with long filler necks. No vent tube and the air coming out burps the gas back on you out of the neck or you have to just trickle gas into the tank.

The vent tube on the pump goes to the canister up front and lets air into the tank to replace the gas that is pumped out of the tank when you have a non vented cap. An extra hose to run to the front and you have to figure out how to tuck the canister away along with finding one that can be tucked away out of sight but the plus side is that folks don't smell gas at the back corner of your truck on a hot day. We have all got a strong wiff of gas fumes when we walked aound or past a car or truck at a car show.

Hopefully that is gas rated filler neck hose and not a radiator hose. Radiator hose won't hold up to gas for very long.

[51 3600]

Tank doesn't have a vent tube so guess I'll have to drill a hole in the tank and weld in a vent tube from which to run a line up to the filler neck. Filler hose will definitely be gas rated.

[dsraven]

I seem to remember some newer vehicles that use a vent tube inside the filler tube, it is captured at the top of the tube on each end so the air escapes from the top of the tank and vents at the top of the filler. maybe you incorporate that idea? maybe you could drill the tank with a step drill so the hole stays round, and install a gasketed or O ringed bulhead fitting to act as a vent tube spigot. just spitballing so you don't have to weld to a coated tank, never a great weld result.

[mr48chev]

Originally Posted by 51 3600

Tank doesn't have a vent tube so guess I'll have to drill a hole in the tank and weld in a vent tube from which to run a line up to the filler neck. Filler hose will definitely be gas rated.

If you don't have a vent tube you have to run a vented cap it is that simple.

The vent tube to the charcoal filter is for keeping gas fumes from hitting the atmosphere.

The primary purpose of the vented cap or vent tube to the canister is very simply to let air in the tank to replace the gas going out or you end up creating a vacuum in the tank.

Fumes don't go out of the tank unless you are sitting in the hot sun and the air in the tank expands and needs to excape or create a pressure in the tank.

Actually the few times I have smelled gas fumes is when I filled the tank just before I got somewhere where the truck was going to sit out in the sun for several hours. Like stopping and fiilling the tank just before you get to the venue where a show is so you have a full tank and can hit the road right after the event.

[51 3600]

Originally Posted by dsraven

maybe you could drill the tank with a step drill so the hole stays round, and install a gasketed or O ringed bulhead fitting to act as a vent tube spigot. just spitballing so you don't have to weld to a coated tank, never a great weld result.

Thanks for your spitballing! Bulkhead fitting hadn't occurred to me but found several types online that will work. Just have to find a neighbor kid with small hands to insert and hold the fitting from inside the tank by going through the filler hole.

Originally Posted by mr48chev

If you don't have a vent tube you have to run a vented cap it is that simple.

I'm using the stock (? came on truck) filler neck and gas cap. Although I don't see how (no visible pin hole, etc.) the cap must be vented as the original tank only had a fuel line out and the fuel neck in with vent tube. Faded and faintly visible on the gas cap gasket is "?? 55 VENTED". Does that mean it's a vented cap from a 1955?

[dsraven]

drill the hole, vacuum out the drill chips, run a wire through the hole and fish it out the filler or the fuel pump hole, attach the bulhead fitting to the wire, pull it back through the hole, install the seal and nut. no biggie........
whatcha gonna do AFTER breakfast?

[fauXGT]

Originally Posted by 51 3600

Thanks all for the input, very helpful. FauXGT the last pic you posted is exactly the position I’ve figured for my tank. That pic Helps a lot. What did you use to transition from what looks like 2” filler hose to the stock filler neck which is 1.375”?

‘Nother question. Since the in-tank fuel pump I’m using has a vent, can I eliminate or at least block off the vent tube on the stock filler neck?

I got the transition piece here https://www.fillernecksupply.com.
The tank came with a 45* 1.5" but messed up in mockup. Cut it down too short. Ordered a new one from the same place. I'm going to save the old short one, split down the middle and wrap it around the finished one for extra rock/debris protection.

[fauXGT]

B09 is their part # for the reducer.

[vintovka]

FWIW i used a combination of solid Delrin blocks and slabs of Lowes Choicedek to get proper levels on mine The Choicedek can be stacked as needed and works well providing stability and some shock absorbing quality's. It can also be sliced easily on a table saw to get precise thickness.

[dsraven]

you may be able to get your local muffler shopp to swage a piece to the desired size as well.