'70 F100

[AKROVER]

It has been almost 25 years since I installed a Holley Blue in my Mustang, but that wouldn’t be particularly relevant since I had a fuel cell on the floor of the trunk and the pump was mounted directly below. However, I have designed industrial pump installations as part of my many years as an engineer in the chemical industry. You do have a little bit of a dilemma. Holley’s recommendation of installing at a lower elevation is probably a very conservative recommendation, especially for a vane style pump. A pump like that can suck quite a bit. The problem is that if you ask it to suck too hard, it will cavitate which can be damaging. Water based liquids are certainly worse than organic liquids in this regard, but the effect could still be damaging. More likely, though, given the abuse my Holley endured in its life, is that you might not be able to use the entire tank before the pump stops pumping adequately. The other problem with Holley’s advice about elevation is that it is not that simple. The pump can take some negative pressure (vacuum) at the suction with no bad effects, but negative pressure isn’t just about elevation. One consideration that you might want to think about is inlet line size. A 1970 Mustang tank probably has a quarter turn cap with both the float and the pump suction lines attached. Unfortunately, these suction lines are probably pretty small. Think of it as trying to drink through a small straw; you have to suck harder. While that float/suction line assembly might be hard to modify, I certainly would step up the line size immediately at least to the pump inlet line size of 3/8” and larger wouldn’t hurt if you need to travel any distance before the pump. Keeping that suction line distance to a minimum would help, as well. The dilemma is that you won’t know that you are going to have a problem until you have a problem and there is a slight chance that the first time you have a problem, you will damage the pump. And of course if you don’t get that pump low enough, you might have a tank that always has to be at least ¼ full for your pump to operate.

Now it isn’t simply a matter of protecting the pump from liquid cavitation. The other problem is priming the pump. This style of pump can actually pump air, but only to a limited extent. If the suction lines are full of air and you need the pump to suck the air through to get to the liquid, it might have a problem. There are line configurations that might help, but they are complicating and unlikely to be necessary. The good news is that if the pump doesn’t prime, it really isn’t likely to damage itself unless you just leave it running dry for a very long time. You would know the first time you tried whether or not you needed to put in some provisions for priming. I’d have to think about what I would do if the pump wouldn’t prime on its own, but it would probably be a tee just upstream of the pump with a third line that I could either use to suck gas or add gas into the line. I would certainly try the simplest installation first, though.

Now I am with you about not having the pump hanging down where it can get damaged. If it were my installation, I would certainly try putting it at a safe elevation with consideration of limiting that suction line distance and maximizing its size. I would probably try to experiment with finding out how low the pump can pump, recognizing that there is a slim chance that I might damage the pump with my experiment. My tolerance for a $100 mistake may or may not be higher than yours, though. In spite of the lack of real technical data on the pump (I checked the online info and didn’t find any real engineering data), I would place a high probability on achieving a completely successful installation in spite of not following Holley’s elevation advice.

[Maverick]

Great info, AK. Thanks for posting it.

I was thinking about a way to priime the pump if it won't prime itself. There's no evaporative emissions vent on this tank so the only vent is in the gas cap. Was thinking I might weld a nipple onto a spare gas cap and carry that, and a rubber hose, in the truck. I expect, with the pump running, a good blow into the tank would make the pump pick up prime.

The nipple on the Mustang tank is 3/8", as is the stock fuel line in the F100. I'm thinking that should be sufficient. Or, it would be pretty easy to run a bigger one from the tank to the pump. An in-cab fuel pressure gauge would make it easy to know if the fuel delivery system was adequate. Have to think about that.

Think the pump and pre-pump filter will get mounted in the C-channel crossmember behind the tank. They'll be at about the middle of the tank height, will be pretty well protected, and easily accessible back there.

An in-tank fuel pump would be a cool solution to all this. Some are available for carbed engines but they're kind of pricey at around $200.

[GMJohnny]

Maverick .....

I'm no expert on any of these things, but I thought I'd chime in. A question I have is have
you considered putting a fitting on the front or rear of the tank the lowest point, just before
the bend of the bottom of the tank? I think doing this would allow the pump to be "lower"
than the tank, but not hang down so low as to scrape the ground. ( I don't know what the
pump looks like size wise also... ) If the tank has never had fuel in it, it'd be an easy install
with a welder and you can put the fitting where you want it. Just a thought. Also, I've been
involved with putting electric fuel pumps in diesel operated machinery before and we've
never worried about the placement of the pump in regards to the tank. We've always seemed
most worried about the pump getting whacked by construction debris or job-related hazards.
Where I'm going with this is sometimes we've mounted pumps way up high and they've
still done their job. Also to mention is that we usually only get cheapie inline pumps from
a parts store......They are nothing fancy. Now they are only running 80 horsepower diesels
( & less horsepower too ) that don't rev a bunch, so I'm not certain of volume requirements,
but we've always just put them in and they worked... I'm not even sure if this info helps,
but I figured I'd just throw it out there for you.....

GM

[Maverick]

Thanks, GM. If the cheap in-line pumps will pull diesel fuel up, which I assume is more viscous than gasoline especially when cold, the Holley Red should do OK with 3-4 inches of head.

Next question is about alcohol tolerance. The Holley instructions say the pump can't be used with alcohol. Don't most gasolines have alcohol in them today? Holley might be saying no 100% alcohol but if they can't tolerate pure alcohol it seems a few percentage points of alcohol would do them in too. I'm going to take a chance on this one since the pumps are rebuildable. Maybe I'll get a rebuild kit and keep it in the truck.

[Basement Paul]

I ran a Holley electric one in my turbo Pinto for years with no issues and it was my daily driver. I'm sure I put more than 30k miles on that pump. I ran it about 7psi, turned it on manually when I started the car, and shut it off when done. It was mounted on the frame rail which was about the midpoint of the tank height. I knew it was on because I could hear it and feel it (I didn't use any mounting insulators), and I never forgot to shut it off... bzzzzzzzzzzzzzzzzzz.

There was alcohol in the fuel then too. I don't think I'd worry about carrying a rebuild kit, that's what tow trucks are for. You start down that path and you'll have spare batteries, belts, plugs, etc...

-BP

[Maverick]

You start down that path and you'll have spare batteries, belts, plugs, etc...

No danger of that!!!

[AKROVER]

I really think the installation will work fine as described. And your idea for priming should work in a pinch. Hopefully Holley has reduced the noise of those pumps in the last 25 years since Paul and I listened to the buzz. I know mine was really loud, almost loud enough to hear over the open headers of a big block (not really, but without the engine running it was impossible to forget that the pump was running). Of course there wasn't a soft surface anywhere on my car so the result on a street vehicle should be different. Looking forward to your continued progress (and after today, you can tell all your friends that someone from the Republic of Congo is following your project).

[Maverick]

When I was in High School, 100 years ago, a friend had a channeled '32 Dodge coupe with a DeSoto hemi and electric fuel pump -- quite a novelty back then. (Also a hydraulic clutch!) The electric fuel pump was loud and really cool. He'd turn the key on and wait for the pump to stop. Do they still stop when pressure is built up? If they do, I might leave the rubber out of the mount too.

[Maverick]

Got the heater box out from under the dash, cleaned up, painted, and a new heater core in place.



The heater box won't go back in till the new wiring harness is well along.

Got most of the wiring out of the truck today. Only stuff that's still in is the harness from the firewall to the back of the truck.



Here's the new fuse block and wiring kit that will replace the mess on the floor.



WXO, if you feel like working on some puzzles, come on down!!

Lots of things to work out, lots of ties, wire stripping, soldering, and heat shrinking.

[Maverick]

Got started on the wiring. Fuse block is under the dash right by the parking brake pedal.



Took it back out, loosened the wire bundles, and got them moved to come out the side of the block rather than down.

The kit comes with four bundles: front, rear, dash and steering column. I split the front bundle into three: left for front lights, center for engine, and right for battery, elect fan, and right turn signal. Got the three front bundles poked thru the firewall today. Finally found a use for the large bunch of wire ties I picked up somewhere (Carlisle?). Lots of tieing up, cutting the ties, and re-tieing.

Unnecessary wires for power antenna, power windows, cruise control, and radio constant-on were isolated from the harness. Some will get used for other things. Didn't find circuits for the wipers and windshield washer?!?! Shouldn't be a big problem, but why no wiper wires??







WXO will be helping -- we just gotta find a day when we're both available.

[Maverick]

The "E Z Wiring" kit is turning out to be not so easy. With the '70 F100 gauges, lights, ignition sw, wipers, etc, and the '83 or so steering column with flasher sw in the column, MSD ignition box, electric fuel pump, 199X (3G?) alternator, etc., etc., etc., there are a lot of mis-matches. And, I'm not finding wiring diagrams that are complete and accurate for the F100 chassis and F150 steering column. Lots and lots of puzzles for this old brain. The diagrams supplied with the kit are really sparse with nothing at all on the fuse block. Lots of good comments on the internet about E Z Wiring tech support. They picked up on one call but didn't call back on another.

WXO has been over to help multiple days and that's been a huge help. Its lots easier with two people poking wire in and pulling it out, noodling on the puzzles, and holding wires/connectors for soldering. Got the ignition, alternator, wiper motor, MSD box, fuel pump done or mostly done. Think the horn circuit is figured out. Steering column wiring is about 80% done. Never did find a wiring diagram where the number of wires or colors matched the column I have and its not obvious what functions are supported by the 10 wires in the turn signal switch. Still wondering why there are 3 wires on the windshield washer switch??? Did find a pretty good, complete wiring diagram for a '72 F100 (mine is a '70) but it doesn't show colors or sizes.

There will be a low-oil-pressure cutoff sw for the fuel pump but no inirtia sw. Think the oil pressure cutoff sw should serve as a rollover cutoff as well as preventing engine damage with an oil pump failure.

The old points ignitions used a ballast resistor or resistor wire to drop the voltage on the coil to 6V-9V to avoid burning the points. During engine cranking, the starter solenoid would feed 12V to the coil to provide a hotter spark for starting. The MSD ignition takes a full 12V. The 12V feed during cranking will now be used to bypass the low-oil-cutoff switch so the fuel pump will run before oil pressure comes up. There will also be a push-button switch on the dash to bypass the low-oil-pressure sw so, if the truck hasn't run for a while, the carb bowls can be filled before cranking the engine.

In spite of the difficulties, I'm still convinced the complete re-wire was the right way to go. There is a lot of stuff that requires new circuits and the rear lights, radio, and gauges were hacked up pretty good.

[Basement Paul]

It's glamorous work, isn't it?

-BP

[Maverick]

It's glamorous work, isn't it?

-BP

Yeah, right!!

But, you know, after this I might be willing to tackle wiring up an EFI install. Can't be MUCH harder.

[Maverick]

Can you find the LED backup lights?



I may have to copy this.

[wxo]

Very clever. I wonder how effective they are being up so high in the ends of the bed rails. Maybe they should be lower to light up the ground better. Just a thought.