Ls 1 swap fuel tank question

[harp]

my 55 shortbed came with an Ls 1 but the fuel tank was from 55 car? and thrown between frame behind axle. the fuel slosh prevented the truck from launching or running good on less then half a tank. the fuel pickup was on the lower front of the old tank. ive designed a new low profile tank in the same location with baffles and a sump. my question is: the tank builder wants to move the pickup to the top over the sump insert a fitting with a suction tube into the sump. will the inline fuel pump do alright with this type of suction line versus the direct gravity feed style of having the port low and forward in the sump? any comments and help would be greatly appreciated.

[BigDan3131]

Welcome to the forums.


Could you show us the plans of what you want to do and what he wants to do?

[BR3W CITY]

You need a sketch or something to show this...unfortunately the description doesn't make complete sense the way I read it.

If you have a sump (intended low point for fuel pickup), then you will put a fitting at the low point on that sump, and connect the suction side of the fuel pump...or the feed line TO the suction side of the fuel pump. The goal is to keep the pump as close to the sump as you can, while also keeping the pump as low as you can. (so make sure the sump is in the back lowest point, so under heavy accell you still focus the fuel on the pickup point). Technically, you can get away without baffles if your tank is angled towards a sump, and your running an external pump (or use tank foam). Rarely would you pull a hard enough stop or lateral-g to start the motor in one of these trucks, though its possible.

You can still run a sump with an in-tank setup (which I think is whats the second option you described was getting at), but the sump is a little less needed. This would be where baffles are of more use. By mounting an in-tank pump, you lessen the need for a large traditional sump, because you are submerging the pump into the fuel...thereby making it the lowest point in the feed line. On some custom tanks, there is a little "notched" sump" that allows the pump to tuck at the absolute bottom point on the tank, letting you go as LOW as physically possible on fuel without starving. The reason baffle are important here, is that in-tank pumps typically mount towards the low-center of the tank instead of at the low-rear like a sump and external pump. This means that heavy stops and turns can starve the pump easier if fuel supply is low...AND can do so under accelleration also, unlike the other setup. IF you starve the fuel system while launching, you lose power and risk all the other fun problems of running lean.

Thats a really wordy attempt at explaining it...but if you put up a sketch of your idea, we can take a look and see what your working with.

[dwcsr]

Originally Posted by harp

my 55 shortbed came with an Ls 1 but the fuel tank was from 55 car? and thrown between frame behind axle. the fuel slosh prevented the truck from launching or running good on less then half a tank. the fuel pickup was on the lower front of the old tank. ive designed a new low profile tank in the same location with baffles and a sump. my question is: the tank builder wants to move the pickup to the top over the sump insert a fitting with a suction tube into the sump. will the inline fuel pump do alright with this type of suction line versus the direct gravity feed style of having the port low and forward in the sump? any comments and help would be greatly appreciated.

I would want the pump in the tank with at least a 4 liter fuel tray. Suction tubes should be left to mechanical pumps.

You can do something like this with a Tanks Inc Mustang EFI tank
http://67-72chevytrucks.com/vboard/a...1&d=1385158802

You can get the whole setup for about $460. Pump, 16 gal. tank and sender

[harp]

thanks for the replys, the tank is tilted towards the sump, the original setup had the fuel pickup in the front of the tank towards the bottom. the new tank has a sump, baffles, and an inline fuel pump and regulator. should i leave the fuel pickup down low in the sump, or change it to a suction tube that is inserted 8" into the tank from the top into the sump area. the tank builder thinks its safer up top, but i dont want problems with the suction tube filling with air everytime i shut off motor, or problems sucking the fuel up the tube before it reaches the pump. i guess it really doesnt bother me to have the fuel pickup fitting at the bottom of the tank, i realize the problems of having it there, draining tank if theres a leaky hose or fitting. i'm more concerned with the Ls 1 performing the best.

[Hart_Rod]

Originally Posted by harp

thanks for the replys, the tank is tilted towards the sump, the original setup had the fuel pickup in the front of the tank towards the bottom. the new tank has a sump, baffles, and an inline fuel pump and regulator. should i leave the fuel pickup down low in the sump, or change it to a suction tube that is inserted 8" into the tank from the top into the sump area. the tank builder thinks its safer up top, but i dont want problems with the suction tube filling with air everytime i shut off motor, or problems sucking the fuel up the tube before it reaches the pump. i guess it really doesnt bother me to have the fuel pickup fitting at the bottom of the tank, i realize the problems of having it there, draining tank if theres a leaky hose or fitting. i'm more concerned with the Ls 1 performing the best.

Since you are building a new tank, put the pump in the tank! You will save yourself some hassles later down the road and your pump will last longer. Just my $.02.

[JJH Jimmy]

Originally Posted by Hart_Rod

Since you are building a new tank, put the pump in the tank! You will save yourself some hassles later down the road and your pump will last longer. Just my $.02.

X2. put the pump in the tank. I built a sump tray and baffles in the tank i built. Some will say if you have a pump failure it will be easier to swap a new pump, but honestly i could probably swap the in tank pump in the tank i built in an afternoon pretty easily.

[harp]

update,my tank will have the fuel pickup on the front of the tank down into the level of the sump, with baffles. my existing inline fuel pump system will have a constant supply of gravity fed fuel. i found "brass" fittings for everything i need that threads into the tank, 3/8 pipe to 3/8 flare for the fuel lines. i'll be using teflon tape to seal the threads unless someone knows of a problem with that. also any problems using these brass fittings i found at boat owners warehouse, the tank is aluminum ? p.s. i got an awesome custom 8" sending unit from ft lauderdale speedometer and gauges for 66$ thanks for all the help

[BR3W CITY]

Teflon isn't meant to seal threads, nor is it good for gas applications. There is a yellow "tef tape" designed for petroliate and natural gas piping uses that will not dissolve. Or in some cases you can use the various Permatex "sealers" available for the particular use (makes undoing joints much harder).

Brass and aluminum can create a galvanic reaction/galvanic cycle when in contact and introduced to type of catalyst. This creates a much larger discussion, but if the brass and aluminum aren't directly contacting each other...you should be ok.

I have an aluminum fuel cell, and before I switched to Aluminum AN fittings, I was running some Brass JIC fittings (same 37* flare). The points which they met developed a tiny bit of white powder oxidation. Were I to let it continue for a long time, or expose it so something like moisture/road salt/road chemicals, this can eventually do damage.

That being said; using brass fittings in an aluminum tank by itself shouldn't be a problem, just don't interface the two.

[harp]

i'm calling them brass just because they look a similar color. its from marine application i'll have to check for sure. sounds like i may need to look further for a better material.

[BR3W CITY]

aluminum an fittings are pretty standard for fuel stuff on performance app's these days.

[harp]

thanks for the help guys, my local speed shop seems to have what im looking for in the matching blue an fittings