Fuel system help

[Italia's 67]

Hey guys,

Ok I've been doing a bunch of searching and I can't seem to find a good way to go about this. Maybe some one on here has done this correctly.

I picked up a 99 vortec engine for my 67 c20. There isn't provisions for a mechanical pump as I'm sure you are aware. I have a Holley style rotary vane pump and a Mallory return regulator. This is a carburetor setup.

My problem is trying to figure out a efficient way to run a return line. I found a replacement behind the seat tank through LMC that has a 1/4 bung somewhere on the tank. I tried to ask them the location but they had no clue. My concerns with this tank are:

#1 is it too hard on a frame mounted Holley rotary vane style pump to use the stock style pick up

#2 is a 1/4 inch bung too restrictive for a pump that flows 105 GPH at 14 psi?

I really like the idea of the behind the seat tank but if it's just not possible I'm open to suggestion that don't involve $400 aluminum tank at the moment.

[B. W.]

Have a 350 Vortec also, I'm assuming the 1/4" bung is NPT, if so it will work fine as a return (approx. 3/8"). As for the location of the pump, I have a carter mounted on the frame rail close to the same location of the original line. I would have loved to run a stock mechanical pump but the block wasn't drilled & was already assembled. Many machine shops have a jig do drill the fuel pump push hole so you can run a stock style pump. I would have done this if my block was disassembled.

[Italia's 67]

Thanks for the photo. What tank are you using and are you running a return? It is a 1/4" NPT bung.

If I run a 3/8 line for a return to the tank where there is a 1/4" bung wouldn't this bottle neck and cause some restriction? The instructions for the pump say to run a return line same size as the feed or bigger.

Has anybody had any success or problems with a smaller return? And is anybody using the LMC 32-5923 tank?

[B. W.]

I'm not running a return, it's a 5 psi pump. A 3/8" return line will work fine. Most carburetors like 5-7 psi. Not a bad idea to run a regulator, I've had electric carters fail & push too much pressure.

[Italia's 67]

Thanks B.W.? How long do your carter pumps last? Your set up looks great by the way.

Has anybody on here hooked up a return line to their behind the seat tank? Pictures would be really helpful!

[MLB57]

Originally Posted by Italia's 67

Thanks B.W.? How long do your carter pumps last? Your set up looks great by the way.

Has anybody on here hooked up a return line to their behind the seat tank? Pictures would be really helpful!

The tank that lmc just replaced has the 1/4 return it is located towards the passenger side top. Iam running my return for the Holley terminator in the 1/4 return line for the factory fuel sender with no problems
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[Italia's 67]

Thank you MLB that's just what I needed to hear!

[B. W.]

Originally Posted by Italia's 67

Thanks B.W.? How long do your carter pumps last? Your set up looks great by the way.

Has anybody on here hooked up a return line to their behind the seat tank? Pictures would be really helpful!

Thanks for the compliment. I've run carters on may different rigs, both vehicles & boats, I thing they are great pumps for stock applications. I can't remember any of them failing to pump. The last one I had an issue with was on a 500 caddy with a q-jet. It kept sinking the float from too much fuel pressure.