Working on a fuel issue

Discussion in 'Street/strip 400/430/455' started by rkammer, Aug 5, 2018.

  1. rkammer

    rkammer '71 GS455 Arctic White

    I remember reading about your pusher pump a while back, Larry. Is that any more effective than the RobbMC pump in the stock location. I don't see the cost as a major issue either way. My engine dyno'd at 468 HP with the stock manifolds and the most I will ever do is add headers. But, probably not as it's so stock looking now and I like it that way.
  2. Schurkey

    Schurkey Silver Level contributor

    If the return fitting on the pump is dead-headed into the pressure gauge, the gauge will be dampened by the restriction but otherwise it'll read the (average) pressure the pump is delivering to the carb.
  3. Bens99gtp

    Bens99gtp Well-Known Member

    I like the "KISS" rules keep it simple stupid. Not calling anyone stupid. I think the robbmc pump. A proven performer is any easy bolt on and go.

    Just remember when dealing with fluid, if there is one spot in the entire system that has a restriction it restrict the entire system to what can be pushed or ducked through that one spot.

    Normally I would recommend when going to higher volume pump, we need to get bigger line and pick up sizes. But yours used to run 100% before with no know fuel supply problems. Sounds like pump getting tired. I would install a bigger pump for extra insurance, I would get the return working as it should and all should be well.

    Deadheading electric pumps on street cars will heat up electric pumps very quickly. I never put an electric system together without a bypass.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Robb Mc pump is the way to go. The worse thing for an engine is to lean out at WOT. When it lays over, it is getting critical, but the problem can be building and you don't realize it. Just ask Phil Sedlon (70 gsconvt)

    He broke a forged piston ring land running the Stage1 pump to high 11's.
  5. Briz

    Briz Platinum Level Contributor

    You can see the bottom of it in this pic. KIMG0018.JPG
  6. rkammer

    rkammer '71 GS455 Arctic White

  7. shiftbyear

    shiftbyear Well-Known Member

    I'm not sure you need more fuel or at least run a pressure gauge up to the cowl where you can see if the pressure is dropping off. I ran 11.80's @ 113 with a $15 autozone pump, stock fuel line, shifting at 6000rpm. Not questioning your diagnosis, could be fuel, but a low float level could be the culprit. Running a larger needle/seat may cure your problem. Good luck.
    rkammer likes this.
  8. rkammer

    rkammer '71 GS455 Arctic White

    Always good to hear an opposing view. I will definitely run a FP test before spending any money on upgrades.
  9. rkammer

    rkammer '71 GS455 Arctic White

  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Should both be 3/8", I just used that barb as an example.
  11. shiftbyear

    shiftbyear Well-Known Member

  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I have braided line, -6AN from my fuel pump to carburetor. I understand if guys want to look stock, but I would never go back. The AN fittings are so easy to seal. It is actually pretty easy to replace the steel line, you just need a few conversion fittings.

    All you need on the Q-jet side is this,

    On the fuel pump side, this,

    For fuel pressure sender, this inline,
    rkammer likes this.
  13. rkammer

    rkammer '71 GS455 Arctic White

    Larry, looks like either adapter will fit the front of the Quadrajet. One directly into the carb body and the other into the OEM adapter if left on the carb. Is that right? And, if I use the one that replaces the OEM adapter, what fuel filter do you use? And, do you use both a pre and a post fuel pump filter? I may deviate from stock and go this route. It's very clean looking and won't be easily seen with the factory ram air filter in place.

    Lastly, do you leave the fuel pressure adapter in place all the time or, only when you want to check pressure? Where in the line do you put it?
  14. Bens99gtp

    Bens99gtp Well-Known Member

    Float level or needle size could cause the issue the op listed, but was also stated that b4 everything was running great, never said anything about carb adjustments or parts changes b4 problem arose.......I think that's why a lot of ppl overlooked these possiblities.

    But good points
  15. rkammer

    rkammer '71 GS455 Arctic White

    Just to be clear, the Quadrajet was rebuilt and updated by Mark at and has not been changed or modified other than making air valve adjustments. I've tightened it up a little to make sure it's not flopping open and closed when the throttle is nailed.
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Ray, you have the option of using 2 of the 5/8-18 inverted flare to male -6AN adapter fittings.

    One can screw into the fuel pump, the other to the Q-jet filter housing. Then you don't have to make a filter inline with the braided line. When Jim Weise finished my engine, he added the braided line so that I could go from Q-jet to Holley DP easily as each carburetor had a male -6AN inlet fitting. He used a billet inline filter with a fitting on each side of the filter. The filter is under my distributor. I went with the fitting that replaces the filter housing. Here is a picture of the engine with the Holley DP. The braided line is long enough so that I can just move it over and attach it to the Q-jet.

    The fuel pressure take off is permanently attached to -6AN filter housing fitting,

    I use an Autometer electrical fuel pressure gauge that uses a small sending unit. That screws right into the 1/8 NPT hole.

    Here is a picture of the sender attached to the Holley braided fuel log. I bought a second sender for the Q-jet. Don't have a picture of that, but it is right in front of the Q-jet fuel inlet.


    Last edited: Aug 13, 2018
    rkammer and Harlockssx like this.
  17. rkammer

    rkammer '71 GS455 Arctic White

    That explains it perfectly, thanks. Do you run another fuel filter between the fuel tank and the fuel pump?
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I do. I have Aeroquip pushlok -8AN hose in the frame rail. I run a billet fuel filter before the CV Products fuel pump.
  19. oldschool85

    oldschool85 Well-Known Member

    Did the problem occur after making air valve adjustments?
  20. rkammer

    rkammer '71 GS455 Arctic White

    The problem occurs the same whether the valve is very loose or tighter.

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