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Thread: Back to my fuel vapor in the lines.

  1. #1
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    Back to my fuel vapor in the lines.

    OK, I don't know who wrote it but it finally sunk into my big fat head about using the mechanical pump is creating a low pressure in the fuel line, so it will boil easier. So I'm ready to go electric back as close the the tank as possible. Is a pump like this OK? https://www.summitracing.com/parts/crt-p4594
    Will a pump like that run constantly? At one time many years back I had an electric pump but it sounded like a little jack hammer, and it only hammered when the pressure went down. I sure don't want one like that because I could hear it with open headers!!! The one thing that bothers me is the 1/4"NTP fitting that goes to a 3/8" hose. Why a 1/4"? I just had the 55 out today and it's warm for winter but was under 60° and my fuel pressure dropped before I hit 3rd, but it wasn't bad enough to make it stumble, well also because I left off the throttle. I'm sure a new tank with an in tank pump would be the best, but I'm sure hoping I don't have to go that far.

    I also have heard more than 1 person say they ran an electric through the mechanical just in case the electric failed. I suppose because mechanical pumps tend to give a warning and die more slowly than an electric. Anyone running there's like that? As much as I'd like that kind of backup, I also would be concerned about it helping to raise the fuel temperature. It does have a 1/8" spacer for heat insulation from the block, but with the hot air from the radiator the mechanical pump gets pretty hot.

    So to sum up, I was w, wr, wrrr, wrrroo, wwwwrrrooo, ah, not correct.
    Tony

    1955 Bel Air Sport Coupe

  2. #2
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    There must be something else going on not caused by using mechanical fuel pump, which work great. Some pictures of your setup would be a great help to diagnose your fuel pressure issue.

  3. #3
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    A 50 gph electric pump won't support much power.

    An electric pump needs a proper installation, most importantly gravity feed or in-tank installation.

    A good mechanical pump with a proper installation will support 550 rwhp, or about 650 hp at the flywheel. Are you there?

    If you're having problems, look for an air leak, a pickup problem, or a bad regulator. You should have a 3/8" line from the pickup to the pump.

  4. #4
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    Pictures, yes I keep forgetting about pictures. I'll work on that.

    Electric pump, gravity feed ... my tank has a drain plug! Actually I thought of that last week but I forgot it again until now. At least if I had a leak I could see it!

    650 at the flywheel? I highly doubt that. The person who held my hand when I was buying parts guesstimated at either 450 or 475HP, I forget which. Since that time for various reasons I've doubted the original calculated 10:1 static compression, I believe it's higher. Cranking compression averages 210psi. The big unknown factor is because I didn't CC the heads. Still ... 650HP? I don't think so. Any idea what it takes for a 12.5 second 1/4 mile with poor traction street tires on a poor traction street. Oh and with 3.42 gears?

    Also, this "running out of fuel" problem has been with me before the motor was redone, when it for sure had a lot less HP, a LOT. At first I was running the original line, then replaced it and the pickup with 3/8". It's been through two fuel pumps and two regulators.

    The one common denominator throughout years of this has been HEAT. A warm day with winter gas, or a hot day with summer gas. Get up to 75° on winter gas and forget it. Right now I have a fuel pressure gauge taped on the outside of the windshield. I had never known till recently just how often the pressure goes down but is still enough to keep it running.

    Recently I learned about 99% of gasoline in CA, and some in a few major cities with smog problems, they have laws that really increase the boiling point (REID vapor pressure) of gasoline. That's one good thing about their rules concerning pollution, good gas!

    I'm really thinking going from the drain hole to an electric pump. Just need to be sure to get a pump that is up to the task.

  5. #5
    Registered Member chevynut's Avatar
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    GO back and read your prior thread on this.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  6. #6
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    Quote Originally Posted by chevynut View Post
    GO back and read your prior thread on this.
    I did but I didn't find any pertinent info except I did put the fuel gauge on the windshield and it's fed from a point close to the carb.
    Although I could have missed something.
    Tony

    1955 Bel Air Sport Coupe

  7. #7
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    eBay item number:

    282735511172

    Like I said last time one of these plumbed with 1/2 line, with a HP mech pump feeds two Holleys. .Probably overkill but it works and looks cool.

  8. #8
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    I have problems with a full tank, so a sump isn't going to help. If I was getting serious about racing yes maybe. But yes, it does look cool!
    Tony

    1955 Bel Air Sport Coupe

  9. #9
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    The idea of rear sump is on hard acceleration when fuel is sloshed back in tank it is forced forward. I will let the Jegs book explain.















    Universal Style Fuel Sump Tanks

    The issue with many factory fuel tanks is they weren't designed to supply the fuel required by high-horsepower motors under hard acceleration. Most factory gas tank pickups are located in the front of the tank, which allows the fuel pump to ingest air during acceleration and thus briefly lose fuel pressure. Eliminate the problem by installing a Competition Engineering Fuel Tank Sump in the lowest portion of the rear of the fuel tank. This guarantees your engine will receive consistent fuel pressure under even the hardest acceleration

  10. #10
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    There are countless oval track race cars out there running 600+HP, 7500+RPM engines, running a mandatory mechanical fuel pump in 90+ degree weather.

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