Dual tanks, 1978 short bed

[HunterRotten]

With the recent decision to do dual tanks on my 1978, I'm trying to mock up a list with my dad on what I will need and how much.

1. I currently have a dash switch arriving in the mail tomorrow, made by ACDelco.
P/N: D7089C

2. Wiring harness I plan on purchasing from gmachinz. This should include everything I need from switch to tank when it comes to wiring, including the selector valve.
http://67-72chevytrucks.com/vboard/s...d.php?t=706027

3. Fuel tank(s) Any recommendations on tanks? I know I need the 1987 tank with the baffles as I am doing sniper EFI. Good idea to go cheapest on rockauto?? I plan on seeing if my current tank has the baffles or not today or tomorrow. It was replaced but not by us.

4. Sending units, recommendations? The unit I have written down is from Spectra.
P/N FG05M.

5. Fuel pumps I plan on doing holley sniper EFI on my big block and need 2 intake pumps for either side that will work with the sniper unit. I am not sure what fuel pump I need, we have a few part numbers written down.
One of which is Walbro 255LPH GSS342

6. Tank brackets I have to find a set of driverside brackets still..

7. Fuel lines What is recommended, and how much ft of line will I need? I am thinking of stainless steel hard lines and stainless braided where needed. This could get expensive though, so any suggestions? Hand held tubing benders?

[gmachinz]

Call Inline Tube-I bought a complete set of lines for my 86 which is carbed but-if you get a lineset for an 87 w/TBI, then you have everything you need you'll just need to modify the main supply line for your EFI. I've always dealt with IT for linesets-a complete set for me from mechanical pump to valve and the crossover lines w/frame clips came to $232....regular carbon tho-not SS.

[HunterRotten]

Ok, thanks. I'll have to give them a call. I have their stainless brake lines and they are really well done and lined up great.

Does anyone have measurements for the hole the tank switch is in on the dash? Like, where and how big? I know it goes on the left of the ash tray, if we get it wrong it's no big deal but I'd like to at least attempt to do it right the first time.

[old Rusty C10]

the cheapest metal tanks I found were Spectra and through advance auto parts

[rich weyand]

Careful. The 1978 tank and the 1987 tank don't have the same diameter filler neck hose.

[HunterRotten]

Originally Posted by rich weyand

Careful. The 1978 tank and the 1987 tank don't have the same diameter filler neck hose.

There's not a difference in the actual tank, right? I was under impression they were the same just 1987 tanks have baffles for the tbi fuel pump. If I use a 1987 tank and have a 1978 bedsides - with round fuel caps, I would just use 1978 filler neck and tubes right?

[rich weyand]

Nope. The hose fitting on the 1987 tank is bigger diameter.

[HunterRotten]

Originally Posted by rich weyand

Nope. The hose fitting on the 1987 tank is bigger diameter.

Ok, is there a way to adapt it properly or a way to get the right tank that is efi/electric fuel pump friendly? I'm just asking because I have it all cleaned up and ready to go on the passenger side and I picked up a OE filler neck online for a driver side 78

[rich weyand]

I would probably slit the hose nipple on the 1987 tank with a Dremel and cutting wheel, squeeze it down to 1978 size (I think 1987's is 1/4" bigger), then braze the slit.

When I did my tanks, I used the later tanks, but my '78 has an '86 box on it, with the fuel doors, so I used all of the '86 parts.

Anybody else had to do this fit?

[HunterRotten]

What do I risk if I run just a standard tank without the baffles w electric fuel pump and Holley EFI?

[100%Chevy]

Tank inlet sizes are 1.5 and 1.75.
The ones I have with the 1.75 inlets have baffels,my tanks with the 1.5 inlet don't have baffels.
This is for my 82,C-30.
Mike.

[rich weyand]

There is also a 1.75" inlet tank without baffles, for 1982-1986.

If the tank gets low, and you suck air because the gas is sloshing around, or because you are on a hill, there is nowhere for the air to go, so you'll kill the engine. On a carb setup, the float bowl will stay open and vent the air until gas fills it up enough to lift the float, so sucking air once in a while is no biggie.

If you never go within two gallons of empty, probably not a problem.

Here's another option. Use one of these metal transitional hose splicers to go from 1-1/2 to 1-3/4. $20 apiece, but it solves the problem cleanly, and safely. You MUST NOT USE a rubber radiator hose splicer. They are not certified for gasoline, and will decompose and then let go. But these metal ones will work just fine.
http://jagsthatrun.com/Pages/Parts_C...eSplicers.html

[HunterRotten]

Originally Posted by rich weyand

There is also a 1.75" inlet tank without baffles, for 1982-1986.

If the tank gets low, and you suck air because the gas is sloshing around, or because you are on a hill, there is nowhere for the air to go, so you'll kill the engine. On a carb setup, the float bowl will stay open and vent the air until gas fills it up enough to lift the float, so sucking air once in a while is no biggie.

If you never go within two gallons of empty, probably not a problem.

Here's another option. Use one of these metal transitional hose splicers to go from 1-1/2 to 1-3/4. $20 apiece, but it solves the problem cleanly, and safely. You MUST NOT USE a rubber radiator hose splicer. They are not certified for gasoline, and will decompose and then let go. But these metal ones will work just fine.
http://jagsthatrun.com/Pages/Parts_C...eSplicers.html

That link seems like the way to go so far! I would need 2 hoses and 4 hose clamps per side, but I guess that's okay.

The hill thing is a bit of a concern and something I've thought about, considering our driveway is a hill at about a 40 degree angle if not worse.

[gmachinz]

You could braze the openings shut and run dual sumped tanks....race stuff.

[HunterRotten]

Originally Posted by gmachinz

You could braze the openings shut and run dual sumped tanks....race stuff.

My dad says it's not a good idea to put an aluminum fitting on the bottom of a fuel tank on a lowered truck, he thought that was a funny suggestion.

[gmachinz]

Well heck no...a sump has rear fittings-a properly designed sump also has fuel even hard hard braking-but if you have a severely lowered truck, I would not suggest an external fuel pump as you mentioned since the pump needs to be positioned slightly lower than your fuel tank so it never draws air and cavitates-that will kill it in a short amount of time. Just get the 1987 stock type fuel tanks and go with the Walbro 255 pumps-you'll be good then.

[gmachinz]

That JTR site is awesome! I have an 86 XJ6 I'm rewiring GM style and I need to address them damn dual tanks....

[HunterRotten]

Does anyone have a part number for the TBI tanks with the baffles?

[HunterRotten]

Here's what's available on rockauto..

[rich weyand]

LMC, page 51.

[HunterRotten]

I'll have to email rockauto to see, I don't really want to deal with LMC shipping on a $100 fuel tank x2.

[HunterRotten]

I sent an email to spectra about the GM11C 16 gallon tank and they said that it does have baffles inside of the tank. Ordering them from rockauto seems to be the cheapest I have found.

I also sent inline tube an email and got a message back with a bunch of different part numbers and costs for fuel lines both stainless and standard steel. If anyone wants that list I can post it here later.

The next item of concern is the fuel selector valve itself which is a part of gmachinz kit. It has a stock-type fuel selector valve. We aren't concerned about the selector valve itself but the plastic hose barbs. My dad raised a good point about them, how do you keep a line holding a lot of pressure (EFI setup/electric fuel pumps) from pushing itself off and spraying fuel on everything?

[gmachinz]

Here's some ideas I pulled from another site....mainly because I like different ways of accomplishing the same objective. First, you need to use fuel injection hose that is rated for high pressure i.e. more than 50 psi. The rating on the hose must read: SAE 30R9. You can tell also by the blue inner elastomer liner it has-this type of hose is good up to 180 psi.

Next, to secure the hose to both your hard lines and your Pollak valve, simply use fuel injection band clamps. While on the topic of securing the FI hose, check out the method used in the pics I attached-shown is a guy using a compression fitting as normal only to "compress" the ferrul tight to the line-he removes the fittings leaving the ferrul in place and cuts off the fitting. Then, he slides the FI line over the ferrule (and it is indeed a super snug/tight fit!) and secures with a FI band clamp.

This is a good, budget friendly way of adding FI hose to both your fuel line and the Pollak switching valve. The FI band clamps work-after all, Pollak wouldn't offer a 65 psi valve if plastic barbs weren't going to "hold" onto the fuel line-just make sure to use the correctly rated hose and related band clamps and you'll be ok!

[Sik66]

Good idea!!^^^^

[Damien]

The compression fitting idea is pretty neat and I could see doing this in a pinch, but for the number of times this would need to be done to build the fuel system I think you could use a flaring tool to put a bubble at the end of the line. Also look into fuel injection hose clamps instead of a standard worm clamp. The fuel injection clamps have a radius on the edge so they will not cut into the hose.