Is my gas tank vent sufficient?

[fang508]

So I am dropping a new engine and a new undercab mounted gas tank in my 86 gmc sierra and I want to be absolutely sure I have all of this right. My original gas tank sender only had an inlet and return line without a vent (2 nipples). My old tank also has the filler neck tube and what looks like a filler vent tube that connects to the tank and filler tube and that is now swapped to my new tank. While my new gas tank is OE, the sender I bought is the same style except it has a vent, inlet, and return on it (3 nipples). My mech fuel pump only has 2 nipples one from the tank and one going to the carb. I have broken in the engine and everything seems fine. I use a mech fuel pump that has a max pressure around 6.5 lbs which according to every forum I look at is the max safe running pressure for my edelbrock 1405 carb. On the gas tank sender I took 6" of fuel line and looped the return nipple to the vent nipple since I don't have a fuel pump return, an originally vented tank, or a charcoal canister system. I believe I have a vented gas cap but I am going to replace it to be sure. Aside from potential fuel odor are there any bad consequences doing this? I will be running open long tube headers for awhile and I want to eliminate the potential for any gas fume explosions..

[tucsonjwt]

I am not sure about your setup, but I have an 83 C20 which came from the factory with 3 nipple sending units. 3/4 ton trucks were considered heavy duty in 1983 and did not need an evap canister. The third nipple on my truck has a short piece of fuel hose capped by a one way plastic valve (same as the one on the differential vent.) I extended the vent hoses on the dual tanks to terminate just in front of the rear bumper and installed valves there. This keeps the fuel odor away from the cab but you can smell it when you are at the back of the truck.

[fang508]

Well this truck is a k2500 that used to have a 6.2l diesel in it so it probably did not come with an evap system at all. The only real thing I am concerned with is fumes leaking pass the loop I made and igniting due to my open headers.

[74CustomK20]

I'd just run plenty of hose so it doesn't kink and use hose clamps.

[Bostonlocalbulldog]

This is what I did.

[fang508]

That actually looks pretty good boston. I think I might do something similar. If i did though, I wouldn't know what to do with the fuel return line since my fuel pump doesn't have one..

[cadillac_al]

I'd get a fuel pump with a return line like the factory started doing in the 70's. I don't know of any down side.

[hatzie]

The upside of the return line is no vapor lock.

I recommend SAE J30R9 hose on the sender to line sections and German Fuel Injection, Constant tension band clamps, or Oetiker Ear clamps rather than worm clamps. Small worm clamps do not work well. THe above pictures show the Fuel injection clamps on the supply and return lines. Clamping the vapor line is not really necessary it's completely up to you.

The fuel fill neck line and fill neck vent line can use worm clamps but I recommend Breeze Liner clamps with a tail covering the worm slots or better yet the spring loaded constant tension clamps rather than standard hardware store worm clamps.

I wrote an article on hoses and clamps.
http://67-72chevytrucks.com/vboard/s...d.php?t=696742

Bostonlocal that looks very clean Kudos on using good clamps that don't loosen up on the fuel lines.

[fang508]

Alright so I have an idea. What if I used one these filters? http://www.jegs.com/i/RestoParts/759...FVQ8gQodGvYCxg

I has a 3/8 inlet and outlet with a 1/4 vapor return/vent. If I bought one of these couldn't I hook that up to the engine bay return line and use boston's setup for the tank vent?

[hatzie]

Why get an obscure fuel filter when you can get an easy to source fuel pump?

[fang508]

Alright so I found this pump on summit https://www.summitracing.com/parts/c...make/chevrolet. I believe this will work. It maxes out at 6.5psi which is edelbrock max psi before problems start to occur and has a return. Also what are those vapor fuel line plug vents boston is using called? I cant seem to find them.

[hatzie]

Originally Posted by fang508

Alright so I found this pump on summit https://www.summitracing.com/parts/c...make/chevrolet. I believe this will work. It maxes out at 6.5psi which is edelbrock max psi before problems start to occur and has a return.

Also what are those vapor fuel line plug vents boston is using called? I cant seem to find them.

That pump should work just fine.

The vent? Try Dorman 14689. It's actually an Axle vent but they're the same thing. The little cap keeps the mud wasps from filling the vent in.

Your vent line on the sender usually has a little mesh helmet to keep from sucking raw fuel into the vent. Return is an open tube. Suction will have a sock or a fitting to install a sock.

If you notice a smell of raw fuel it's not difficult to plumb up an evap charcoal can. The bowel vent is inside the air cleaner so there are only three connections to the can.

1. The vent line(s) that run from the tank to the can Use a mix of steel line or even hard vinyl fuel line and SAE J30R7 evap or SAE J30R9 fuel hose.
2. The purge valve vacuum signal tees into your distributor vacuum advance from a ported vacuum on the carb.
3. The purge hose tees into the PCV valve vacuum hose using SAE J30R7 or SAE J30R9 hose running to manifold vacuum. Good excuse to replace the old soft PCV hose with new SAE Hose.
4. The carburetor bowl vent is capped since the Rochester carbs typically vent inside the air cleaner.

[fang508]

Well I went ahead and bought these here:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The clamps arrived today and they went on quite nicely and didn't chew into the hoses like the worm gears did. I am going to set my system up like Boston's and see how it works once that vent plug arrives. Btw what size is the fitting on these fuel pumps? I can use my old one it's kinda beat up and bent but it doesn't leak.

[hatzie]

Originally Posted by fang508

Well I went ahead and bought these here:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The clamps arrived today and they went on quite nicely and didn't chew into the hoses like the worm gears did. I am going to set my system up like Boston's and see how it works once that vent plug arrives.

The right clamps make it much easier to work on, they look cleaner, and they don't loosen up either.

Originally Posted by fang508

Btw what size is the fitting on these fuel pumps? I can use my old one it's kinda beat up and bent but it doesn't leak.

5/16 or 3/8 hard line should thread right into the outlet fitting. Just take it to the parts store and check the fit.