external fuel pump ?'s

[Jonboy]

How many of you guys are running an external pump, and which one did you go with? I have been trying to plan out my swap, and it looks like an external pump would simplify a lot. My truck currently has dual tanks, and I really don't want to have to source all of the '87 only switching stuff, run wires, etc.

My '74 has the manual push/pull switching valve, but it is feed only. There is only a 3/8 and 1/4 lines on the current sending unit(s). I do have a pair of newer tanks with a 3/8 feed and 5/16 return I was thinking of using. Could the feed portion of the current valve be used, and run 1 new 5/16 return line to the left side tank, or do I need a return in both tanks? It looks like the external pump would run between the switching valve and engine, correct. I may be overthinking this, please tell me if this is the case. Any help would be appreciated. If my thoughts are completely off base, let me know that too.

[Indian113]

When I did my 5.3 I used a external pump and regulator kit from Speedway. The pump is a MSD puts out 43 gph at 40 psi. The kit sells for $169.99,bare in mind I find that it's a lot louder than the external pump I had for my sbc.

[Clyde65]

I have a pierburg pump from turnkey engine supply, overpriced but you won't need another one. It supply's plenty of fuel with a -10 input and -8 output. It is very quiet considering its external.
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[68GMCCustom]

I have a external walbro 255 like this mounted on the frame near the rear mounted tank, running thru a Vette regulator w/return, then s.s.flex line to the port on the fuel rail.
made my own mount w/radiator hose and hose clamps.

[BR3W CITY]

I'm running a "generic" walborough 255 on the rear cross brace. I've got a sumped 16gal cell between the rails and it feeds there from some -8 line.

Does the truck lift gas to a "main" tank and then pump to the engine from there, or does it run 2 external pumps, one for each tank?
If its just a transfer pump, I'd imagine you could keep that all the same and just rewire and replace the "main" tanks pump with a high flow internal or external.

[ls1nova71]

I've never done dual tanks, but I'm going to imagine you'll need an 87 valve at least. You need to return the fuel from the same tank its being pumped from or else you will overflow one tank.
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[Jonboy]

Originally Posted by ls1nova71

I've never done dual tanks, but I'm going to imagine you'll need an 87 valve at least. You need to return the fuel from the same tank its being pumped from or else you will overflow one tank.
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That is what I was afraid of. The valve that was on my parts truck said it was good to 65 PSI, but I don't think it will energize the fuel pump. Seems like the switch in an '87 sends power to the pump, while the 86- down ones do not.

I have the return style fuel rails also. Can the regulator be bypassed and use the Corvette style filter/regulator, or does it need to be swapped out for a feed only type?

[ls1nova71]

Are you planning on running two pumps? If not, your pump will be after the switching valve so pressures will not reallly come into play on the valve since it will be sucking the fuel through it. Your problem is going to be in the return. On an 86 and older., is there any kind of return line built into them? An 87 would have to have a return, that's why I would suspect you'll need the newer valve, powering the pump will be just directly wiring it. The 87 probably does change the power to the two different pumps, but with only one it shouldnt be a problem.

As for trying to make your rail returnless, I can't see a reason to do so. You alr eady have a regulator on the rail, and by changing, all you're doing is going to an expensive fuel filter and using essential ly a disposable regulator. Just run your return line and use the more readily available and cheaper fuel filter and be done with it.
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[Jonboy]

I got a better look at this today at work, where I currently have the truck. The original switching valve is on the right side of the truck. It has 3/8 feed, and it looks like it might be 1/4 return. This one is pretty beefy looking, and looks like it is in pretty good shape. I see the feed out, and 2 inlets in, and the vent/return has one out (in?) and 2 in (out?). There seems to be a return line going to the front of the truck, and I do not see a charcoal canister. The truck was originally equipped with a 454, but that has been replaced with a 350 with a Holley carb, an inline dinky electric fuel pump, and a mess of hose.

I also have a parts truck (frame) that is an '86. The tanks have a 3/8 feed, 1/4(?) return, and 5/16 vent. Does this sound right? I was thinking I could run a new 5/16 hardline to use the vent port, vent at the 1/4 port, and feed from the 3/8 port. The only thing I wasn't sure of is the switching valve. How much fuel is actually returned? Could the 1/4 ports be utilized for the return? Or should I just go the easy route and scrap the dual tanks, run 1 tank on the left side, and run new hard lines? If I did that route, I could just pick up 1 '87 tank and sender, run an intank pump, and be done. It will be a stockish 5.3; this sounds like the least hassle. I was just worried about not having enough fuel capacity, so possibly running the dual tanks would help.

[Hart_Rod]

Board member glock35 made a similar dual tank setup work.

http://67-72chevytrucks.com/vboard/s...d.php?t=350986

[Jonboy]

Originally Posted by Hart_Rod

Board member glock35 made a similar dual tank setup work.

http://67-72chevytrucks.com/vboard/s...d.php?t=350986

Yeah. I reread that thread a few times too. I am pretty sure that truck was already converted to TBI when he started, so the tank wiring and all was there.

I have my truck here at work, but it is a PITA to crawl around it in dress clothes. It looks like the ports on the switching valve are removable, so it might be as easy as changing the return ones to a 5/16" hose barb. I think I am going to switch sides on the switching valve assembly, and run new hard lines back to and between the tanks, so I know what I have. I *think* this will work.

[Jonboy]

How much fuel is actually returned on a stock engine? Would a 1/4" return port work? Also, what is a good external pump for a stock engine. I don't want to starve the engine, but I may not need a 255 LPH pump, either.

[BR3W CITY]

stock size on most of the returns is 5/16, and thats anywhere from the 4.8 all the way up. I've seen larger used on aftermarket rail setups but thats a different story.
Personally I wouldn't go smaller.

[Jonboy]

That's what I kind of figured. What is everyone doing for return lines? The senders I have have a 3/8" feed, a 1/4" return, and a 5/16" vent line. The return line goes down into the tank about 3", but the vent (5/16") does not. I have to run a line back to the tanks, so the 5/16 line isn't so much a problem as the termination at the tank is. I've looked at other senders, and they seem to be the same until you get to '87, but those are for in-tank pumps. Do I remove the 1/4" return and epoxy a 5/16" line in- or would that even work?

[Jonboy]

I was a little bored at my desk, so I went to take a look at the sender out in the shop. It looks like it might actually be that easy. I have the 1/4 return out and the hole drilled for a 5/16 hard line.

[ls1nova71]

I would solder or braze it back in rather than using epoxy. If the epoxy cracks it will suck to fix. Jmho...
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[Jonboy]

You are probably right. One more dumb question, and I think I may be through. Can I run regular fuel hose behind the fuel pump (like from the tank to the fuel valve and from the fuel valve (return side) back to the tank? The lines that are currently on my truck are just rubber hose; I was going to replace them with 30R6 or 30R7 spec rather than the 30R9 spec (FI pressure rated) hose if it was safe to use.

I ordered my fuel pump, fuel filter, and lines earlier today, so hopefully I am set. I think.

[Wasted Income]

Though I personally wouldn't do it, you should be fine with "regular" rubber hose before the pump. It's just under suction...no pressure, obviously.


I'm running a sumped tank and a Fuelab external pump. Works great, and is making good power....haven't even turned it to "big boy mode" yet.

[ls1nova71]

I agree with Wasted Income, you can probably get away with it, but I would use fuel injection hose if it were me. FI hose isn't as soft as regular gas hose which I just feel better with. There is a chance, although most likely slim that it could collapse from suction. Probably wouldnt do it right away, but with the ethanol in gas these days it tends to break down rubber hose and would do it from the inside.
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[BigDan3131]

Originally Posted by ls1nova71

I agree with Wasted Income, you can probably get away with it, but I would use fuel injection hose if it were me. FI hose isn't as soft as regular gas hose which I just feel better with. There is a chance, although most likely slim that it could collapse from suction. Probably wouldnt do it right away, but with the ethanol in gas these days it tends to break down rubber hose and would do it from the inside.
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Use the FI hose it will save you the hassle and money of redoing it again with the normal rubber hose.

[Jonboy]

That looks pretty serious. I am going to be doing good to get it running in a basically stock configuration. I guess I should go ahead and make up some hard lines to go across the rail. It shouldn't be *too* hard.

[BR3W CITY]

My .02 ; the regular stuff is all around softer, and despite the lack of pressure, the pump will create suction, which could cause a partial collapse or ease in kinking on the line (this isn't super likely on a line that small, but it is possible). Were the hose to kink or collapse, it would restrict the working internal diameter and create more restriction on the line and thusly require the pump to work harder, which can lead to premature failure.

That and if your using regular line, your probably using regular clamps as well, also not advised. Plus no track will like you running large amounts of rubber line either way, and were anyone to notice it was non-fi line you'll fail tech.

[Wasted Income]

Originally Posted by BR3W CITY

That and if your using regular line, your probably using regular clamps as well, also not advised. Plus no track will like you running large amounts of rubber line either way, and were anyone to notice it was non-fi line you'll fail tech.

Back when I used to race at an IHRA track, the max was 12" of rubber fuel line from tank to carb...any more than that, and you'd fail tech.

Didn't matter if it was "fuel injection" or "regular" rubber hose.

[BR3W CITY]

Originally Posted by Wasted Income

Back when I used to race at an IHRA track, the max was 12" of rubber fuel line from tank to carb...any more than that, and you'd fail tech.

Didn't matter if it was "fuel injection" or "regular" rubber hose.

Yep thats still true at NHRA tracks as well. I was referring to failing tech by seeing ANY regular rubber on the FI cars, let alone over 12" for any reason.

[Jonboy]

The truck already has rubber line between the tanks, with no steel. I am going to make up some steel hard line to go from the fuel pump forward, so making a pair that go between the tanks shouldn't be a major hurdle. I already bought FI clamps in bulk, so those will be swapped out.

It's a little embarrassing to admit, but I hadn't ever really bought parts online before, other than ebay, etc. I work at a Chevy dealership, so I usually just call the parts department and let them source stuff for whatever junk I am tinkering with. I bought pretty much everything I need from Rock Auto, and it was a lot less than I thought. I was also amazed with the non performance parts Summit carries. I guess the internet is not just for porn anymore. Who knew?