Fuel Pressure ?

Discussion in 'The Venerable Q-Jet' started by Quick Buick, Nov 28, 2018.

  1. Quick Buick

    Quick Buick Arlington Wa

  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    My 7042240 QJ will take 8-10 PSI no problem. Nozzle drip is usually because the throttle is open too much. Early QJ are limited to 6 because of weaker float design.
     
  3. Quick Buick

    Quick Buick Arlington Wa

    Thanks Larry..
    I'll warm her up in a few start with the old carb first, get some numbers on paper on were she is at... timing, RPMs, Vacuum inches.... Then get the new one on and start messing with her again.
     
  4. Quick Buick

    Quick Buick Arlington Wa

    Ok motor stats
    570 RPMs
    Vac 3-4. All vac ports plugged..
    Vac at 1200 17ish at this point runs great to the ear, didn't check tailpipe.
    timing 12 at 570RPMs

    Off to get some more WD40. and FP fittings
     
    Last edited: Nov 29, 2018
  5. johnriv67

    johnriv67 Well-Known Member

    If you are only drawing 3"-4" inches of vacuum then you want to turn your idle up to around the factory setting between 650-800 depending on what engine and transmission you have. I'm guessing the 400. You won't be able to run power brakes at that rpm and vacuum and will likely stall the car when you drop it into drive.
     
  6. Quick Buick

    Quick Buick Arlington Wa

    I hear Ya John. I think the big problem is I cant get the nozzle leak to stop.
    I just took it for a put up and down the street. I had to feather the throttle the whole time.

    FWIW 570-620 is what the old carb idled at and worked. if I brought it up t0 650-800 she would not stop running when I turned the ignition off.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    If you are only getting 3-4" of vacuum, that's a pretty big cam and it will need more timing at idle. Most Q Jets will also need some modification to the idle side of the carburetor. The reason for the nozzle drip is that the throttle blades are open too much so the engine will idle. The front half of the QJ is very efficient, doesn't take very much to initiate fuel flow from the primary nozzles. More timing will allow you to close the throttle blades and still idle. Big block carburetors also have fixed idle air bypass which routes extra air around the throttle blades. Small block carburetors won't have this.

    With a cam that big, you'll need to buy a QJ that is specifically calibrated for your engine. You can't use a QJ meant for a stock application or other make of car.
     
  8. Quick Buick

    Quick Buick Arlington Wa

    OOPPPPS Me Bad the came is not that big

    Old Carb Stats
    RPMs 550-600
    Vac. Idle @ about 12inches
    timing Idle Lets call in 11

    Im Sure something happened in shipping.. At this point Ive removed top of carb checking Float level.. Couple of the screws were on the not so tight side in the primary bay by the nozzle..
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Big enough for the QJ to need calibration. Out of the box holley DP will work on virtually any engine. Not so with the QJ. The reason people dislike the QJ is because they think you can just find one, any one, and bolt it on anything. That won't work. They are different. We have 2 guys right here on V8 that can do the calibrating, it's more than jets and rods.
     
  10. Quick Buick

    Quick Buick Arlington Wa

    At this point of time I Put a pressure regulator on got the nozzle to stop dripping & Vac up to about 10.. I hope I didn't speak to soon.. Cant or won't try get carb to run right because now I got fuel line leaks.. Tackle those tomorrow.. Get them leaks fixed then tune the Carb.
     
    Last edited: Nov 29, 2018
  11. Quick Buick

    Quick Buick Arlington Wa

    Ok Im having major problem with these cheap hose clamps.

    How many of you guys are needing the use a pressure regulator. with a a stock type fuel pump?? Im thinking new fuel pump from NAPA or Advanced auto parts.
     
  12. Quick Buick

    Quick Buick Arlington Wa

    Well this is going to be fun.. I looked on rock auto at multiple fuel pumps for BBB Max pressure range from 6.5 - 8
     
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I use an expensive NASCAR type pump made by CV Products. It puts out 8-9 psi and I have no problem at all with my QJ or 4150 type DP carburetor. The stock pump should not be flooding the carburetor. Send it back to Mark and let him look at the float setting and needle/seat.
     
  14. Quick Buick

    Quick Buick Arlington Wa

    I poped the top off and checked both Needle&seat looked great.. Float level was fine,,, I lowered the level just a bit. put her back together. put back on motor, Drip slowed down. Vac went up from 3 to about 5. Put a crappy mr gasket PR on... drip stopped vac up to 10 . Mark went over this carb with a fine tooth comb.. It's not its first dance on the motor . I truly believe its the FP be cease when you crack the line that thing streams gas out over the grill.
    I don't know why the Olds carb don't leak. But that carb is not quite right..

    From what I understand their is a pressure regulator built in to the stock pumps and they do fail on rare occasion, usually the pump goes weak or dies first.
     
    Last edited: Nov 30, 2018
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Could be, you should measure the pressure.
     
  16. Quick Buick

    Quick Buick Arlington Wa

    Thought about measuring, But Im have no luck with the hose clamps on the FR to get to stop leaking.

    Napa has a 6.5 lbs. pump for 35$. it will be here later today . rock auto has a 8 lbs pump but thats a week out.
     
  17. Quick Buick

    Quick Buick Arlington Wa

    Well I be damed I've been fighting line leaks,, turns out to be the new mr gasket fuel regulator is leaking...
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Don't you just hate that when new parts are defective out of the box? Return it and don't buy another one. You should not need a regulator for a stock pump and Q Jet.
     
  19. Quick Buick

    Quick Buick Arlington Wa

    That's what the plan is. swap PR. for FP. with some change back same Napa store.
     
  20. Quick Buick

    Quick Buick Arlington Wa

    Darn it.. failed again. Sent Mark a vid He said Box her up... That is some of the best Customer service Ive had. Thanks Mark.
     

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