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Thread: A few fuel tank questions

  1. #1
    JohnK's Avatar
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    A few fuel tank questions

    Hey all,

    I'm getting back to my build after a few months off. I'm currently working on the fuel tank, and have a few questions. FWIW - I'm using the following upgrade items:

    - Pro-M fuel pump hanger with Walbro pump
    - Breeze big-bore check valve
    - Ford OEM filler neck seal

    I've got the tank mostly together and ready to install in the frame, but have a few questions:

    1) the FFR kit came with a round profile o-ring for the fuel pump hanger. The Pro-M hanger came with two flat o-rings (a wider one and a narrower one). Does it matter which of these three I use? I've currently got the wide flat one on there, but now's the time to make the change if needed.

    2) I've read that some folks use Permatex form-a-gasket on the fuel gauge sender (presumably with the supplied round profile o-ring). Should I also be using the Permatex on the fuel pump hanger gasket?

    3) I'm trying to get the rearward ends of the tank straps in place prior to lifting the tank in place, but the eyes on the straps are nowhere near big enough for the 3/8" bolts to be able to pass through. Is there a trick to enlarging these without completely mangling them? I've tried to see if I could lightly tap the bolt through with a rubber mallet, but it's waaaay off from fitting through there. would replacing these with 5/16" x 2" stainless bolts (rather than the supplied 3/8" x 2") be a bad idea? I'd still use 3/8" bolts on the front ends of the straps (probably stainless 3/8" x 2.5")

    Thanks,
    John

    Last edited by JohnK; 04-24-2020 at 08:28 PM.
    MkIV Roadster build: Gen 2 Coyote, IRS, TKO600. Ordered 10/24/18. Delivered 1/29/19. Engine installed 8/8/21. First start 9/12/21. First go-kart 9/17/21. Off to paint 4/11/22. Back from paint 12/30/22. Build thread here.

  2. #2
    Senior Member MSumners's Avatar
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    For the bolts to go through the strap I had to use a large drift punch and hammer to round them open a bit.
    Coupe Kit Delivered 11/10/23

    Roadster Build thread: 2019-2022 https://thefactoryfiveforum.com/show...4-Build-Thread

  3. #3
    Senior Member egchewy79's Avatar
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    hit the looped end of the strap to make it more round and less tear drop shaped. this is how i got my bolt to fit. I used the supplied o ring for the fuel sender instead of permatex. no experience with your pump, but i used the supplied o ring for my in tank pump.
    oh, and fyi, get a longer bolt for the PS strap where it attaches underneath the car. tighten it up a bit and then you can switch back to the supplied bolt if you'd like.

  4. #4
    Senior Member rich grsc's Avatar
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    Do NOT use Permatex on the o-rings, lubricate them with motor oil.
    Mrk III, 331 stroker, Borla stack injection, T5, 3:55 IRS, Power steering and brakes. Kleiner body & paint

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  6. #5
    Senior Member BEAR-AvHistory's Avatar
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    Did exactly what egchewy79 did & used motor oil on the gaskets. Never bothered to swap the PS bolt back.
    Kevin
    MKIV #8234
    Coyote '14/TKO-600/3-Link 3:55 Rear
    I love the smell of 100 octane in the morning.
    NITTO NT01 275X40X17ZR - 315X35ZRX17
    Delivered 2/7/14 - Plate "COYOTE NC1965" 3/25/15

  7. #6
    Senior Member phileas_fogg's Avatar
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    Quote Originally Posted by rich grsc View Post
    Do NOT use Permatex on the o-rings, lubricate them with motor oil.
    What Rich said. I followed the F5 video instructions & used fuel safe gasket sealer. A few months later, I had leaks at both the fuel level sender & the fuel pump. When I dropped the tank to find out what was going on, I discovered the sealant had crystalized. I replaced the gaskets (lubing them up so the rotating flange wouldn't tear them up), and all is well.


    John
    MK IV Roadster #8631
    Ford 302, Holley Terminator EFI, T5z, 3.55 Rear End, IRS, 17” Halibrand Replicas (9” front, 10.5” rear), Nitto 555 G2’s (275/40ZR17 front, 315/35ZR17 rear), Fast Freddie’s Power Steering, F5 Wilwood Brakes, FFMetal’s Firewall Forward, Forte’s Hydraulic Clutch & Throttle Linkage
    https://www.ffcars.com/threads/phile.../#post-4776313

  8. #7
    JohnK's Avatar
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    Thanks everyone. I got the tank assembled and ready to install. Waiting on some longer bolts for the front, as I couldn't get the tank straps onto the 2" bolts.
    MkIV Roadster build: Gen 2 Coyote, IRS, TKO600. Ordered 10/24/18. Delivered 1/29/19. Engine installed 8/8/21. First start 9/12/21. First go-kart 9/17/21. Off to paint 4/11/22. Back from paint 12/30/22. Build thread here.

  9. #8
    Member aspbite's Avatar
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    Quote Originally Posted by JohnK View Post


    3) I'm trying to get the rearward ends of the tank straps in place prior to lifting the tank in place, but the eyes on the straps are nowhere near big enough for the 3/8" bolts to be able to pass through. Is there a trick to enlarging these without completely mangling them? I've tried to see if I could lightly tap the bolt through with a rubber mallet, but it's waaaay off from fitting through there. would replacing these with 5/16" x 2" stainless bolts (rather than the supplied 3/8" x 2") be a bad idea? I'd still use 3/8" bolts on the front ends of the straps (probably stainless 3/8" x 2.5")
    Ford used pins instead of bolts on the rear strap mounting locations. Has anyone done this?
    Mark IV, Boss 351c, Toploader, Levy 5 link

  10. #9
    JohnK's Avatar
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    Sorry to come back to this. I've got the tank put together but it's not in the car yet (longer bolts arrived yesterday afternoon), but the OCD part of me can't let the question about which o-rings to use go. The parts package for the fuel tank included both round-profile and square-profile o-rings for the pump hander and sender. There were two more retainers with square-profile o-rings taped to the outside of the gas tank box. To make matters even more confusing the Pro-M hanger came with both a square profile and a wide, flat gasket. I currently have the wide flat gasket on the fuel pump hanger and one of the round o-rings on the fuel level sender, but of course this leads to endless second-guessing on what's correct. The likely answer is that any of them will work fine, so I'd settle for knowing what most people use
    MkIV Roadster build: Gen 2 Coyote, IRS, TKO600. Ordered 10/24/18. Delivered 1/29/19. Engine installed 8/8/21. First start 9/12/21. First go-kart 9/17/21. Off to paint 4/11/22. Back from paint 12/30/22. Build thread here.

  11. #10
    Senior Member rich grsc's Avatar
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    Fox body Fords used the square o-rings, lubed with a thin film of engine oil. Or you can use the round one's, lubed the same. Or you can flip a coin and use which ever one your heart desires. Or setup up a multiply choice poll here on the forum and let everyone have a vote. Or it doesn't make a difference. or or or or
    Mrk III, 331 stroker, Borla stack injection, T5, 3:55 IRS, Power steering and brakes. Kleiner body & paint

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  13. #11
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    I used silicone dielectric grease on mine 14 years ago. I can fill it to the fill cap and not leak a drop. Maybe I just got lucky!
    FFR 5136 Started as a donor...donor guages, engine, trans,etc. Now...TFS street intake,stage 1 cam, GT40p's,24# injectors and 80mm MAF,70mm TB,Z-spec t-5, and PSE Halibrand wrapped with Nitto 555 G2’s. My ever evolving dream car!!

  14. #12
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    I have a tube of silicone O ring grease that I use often. Good stuff to have around for all kinds of purposes. Pretty sure this is the one I have:

    https://www.mscdirect.com/product/details/31735244
    MKIV #7619 complete kit IRS, 351 TKO 500, Delivered 11/13/2011
    First start 12/31/2011
    Gocart 01/12/2012
    completed tags/title 05/11/2012
    http://thefactoryfiveforum.com/showt...-Graduate-7619

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