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Avanti bogs down under full throttle - update

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  • edpjr
    replied
    Thank you for reminding me.[^] The setting of the float level was carefully considered when the carb was rebuilt. If not set correctly it can wreak havoc on performance. We'll have to revisit it anyway when we put in the new plunger and ball valve. And, it sounds like the new R2 fuel pump is going to be installed in any case.

    ps We noted that the Quadrajet carb on my brother's Ram Air T/A gushes fuel when the throttle is pulled back all the way with the car turned off. The AFB 4-V on the Avanti just produces a very weak squirt.

    quote:Originally posted by Avanti82

    Our 82 Avanti with the 305 CI was doing the same thing, idled OK and drove fine unless you put your foot down, then the car bogged down and lost power. We had the carb (Rochester 4 bbl) rebuilt and it was the float level that was causing the problem. Runs like a scalded dog(small dog) now.

    Steve
    edp/NC
    '63 Avanti
    '66 Commander

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  • Avanti82
    replied
    Our 82 Avanti with the 305 CI was doing the same thing, idled OK and drove fine unless you put your foot down, then the car bogged down and lost power. We had the carb (Rochester 4 bbl) rebuilt and it was the float level that was causing the problem. Runs like a scalded dog(small dog) now.

    Steve

    Leave a comment:


  • edpjr
    replied
    I've got a new Carter R2 fuel pump that originally came from Myers. I suspect we'll install it now and maybe get an electric booster pump like JDP suggested too. Apparently, it won't hurt to snake the timing up a bit either. [^]


    quote:Originally posted by maxpower1954

    By all means, rebuild the fuel pump! An older diaparaham will have less volume carrying ability. I rebuilt mine on my R-2 GT and there was a noticeable difference. Debris under a check valve seat can also lead to a loss of performance as you describe. Kits are availiable from D Tbow or Jon Myers. Russ Farris

    1963 GT Hawk R-2 4-speed
    1964 Avanti R-1 Auto
    edp/NC
    '63 Avanti
    '66 Commander

    Leave a comment:


  • maxpower1954
    replied
    By all means, rebuild the fuel pump! An older diaparaham will have less volume carrying ability. I rebuilt mine on my R-2 GT and there was a noticeable difference. Debris under a check valve seat can also lead to a loss of performance as you describe. Kits are availiable from D Tbow or Jon Myers. Russ Farris

    1963 GT Hawk R-2 4-speed
    1964 Avanti R-1 Auto

    Leave a comment:


  • JDP
    replied
    quote:Originally posted by bige

    Correct me if I'm wrong. Your problem occurs when you are cruising along at 40 mph or so and you put your foot to the floor and at that moment the car bogs but then takes off as it's supposed too? If that's the case you do not have fuel pressure issue. Look at the logic of it. While cruising fuel demand is low the bowls are full. When you put your foot down the car has not reached a level where demand is outpacing fuel delivery. Also if I read correctly it doesn't bog when you downshift manually so how come fuel pressure is OK then? Your car and money but poor fuel pressure does not cause the problem you are experiencing if I understood it correctly



    1988 "Beater" Avanti---R5388 @ Macungie 2006
    I don't think it's fuel pressure related as much as volume. Under boost, the factory pump it hard pressed to keep up, even in good condition. A rebuilt, or new mechanical pump might do the trick, but I've had more than a few that need a electric in the back too.

    JDP/Maryland

    Leave a comment:


  • edpjr
    replied
    I may have more than one problem.[|)] My brother said that when he drove it to the body shop on Friday, it ran OK as long as he didn't punch it. But he noticed, quite by accident, that there didn't seem to be much fuel visible in the filter. He checked it several more times and the filter was almost devoid of any gas, whereas we expect it to remain virtually full on most cars. The situation has gotten a little more difficult since my first posting. The car seems to run better if you manually shift it, but it still won't take full throttle at a standing start. Now it doesn't want to take pedal to the floor anytime. It bogs at 40 mph and starts choking back if you gap it at 70 mph. I don't think it could be forced to 100 mph. My brother thinks it is somehow being fuel starved at high RPM. [xx(] The only fuel system component that hasn't been refurbed, replaced or rebuilt is the mechanical fuel pump. All the debris and crap that was is the tank may have ruined it.[}] Any ideas are welcome. We'll check it out. Thanks. [^]


    quote:Originally posted by bige

    Correct me if I'm wrong. Your problem occurs when you are cruising along at 40 mph or so and you put your foot to the floor and at that moment the car bogs but then takes off as it's supposed too? If that's the case you do not have fuel pressure issue. Look at the logic of it. While cruising fuel demand is low the bowls are full. When you put your foot down the car has not reached a level where demand is outpacing fuel delivery. Also if I read correctly it doesn't bog when you downshift manually so how come fuel pressure is OK then? Your car and money but poor fuel pressure does not cause the problem you are experiencing if I understood it correctly



    1988 "Beater" Avanti---R5388 @ Macungie 2006
    edp/NC
    '63 Avanti
    '66 Commander

    Leave a comment:


  • bige
    replied
    Correct me if I'm wrong. Your problem occurs when you are cruising along at 40 mph or so and you put your foot to the floor and at that moment the car bogs but then takes off as it's supposed too? If that's the case you do not have fuel pressure issue. Look at the logic of it. While cruising fuel demand is low the bowls are full. When you put your foot down the car has not reached a level where demand is outpacing fuel delivery. Also if I read correctly it doesn't bog when you downshift manually so how come fuel pressure is OK then? Your car and money but poor fuel pressure does not cause the problem you are experiencing if I understood it correctly



    1988 "Beater" Avanti---R5388 @ Macungie 2006

    Leave a comment:


  • JDP
    replied
    quote:Originally posted by edpjr

    Then do you block off the mechanical pump? If so, what do you do with the line that goes to the super-charger? Who sells the proper electric pump? [?] Thanks.


    quote:Originally posted by JDP

    quote:Originally posted by edpjr

    Indeed, this T-bow kits looks far better and complete. I suspect the top will be coming off the old 4V-AFB again pretty soon for re-work. I've also got a new Carter fuel pump for an R2. If these two items don't get gas flowing properly, I don't know what will. We'll also turn up the timing a few degrees. Wish me luck. [^]

    edp/NC
    '63 Avanti
    '66 Commander
    Electric pump in the rear, most every R2 I've had needed one, the Salt Flats cars had three.

    JDP/Maryland
    edp/NC
    '63 Avanti
    '66 Commander

    I keep the stock pump, just add a low pressure or regulated pump near the tank to assure fuel flow. It helps for quicker starts and vapor lock too. Check some of the other suggestions to0.

    JDP/Maryland

    Leave a comment:


  • N8N
    replied
    if it is an accel pump *bore* problem you may have to have the accel pump hole reamed and sleeved. Not sure who is able to do this, I have never bothered.

    As Sal said, if you go with only an electric pump, you should have a boost-referenced regulator near the carb. Fortunately you already have a return line installed to make this somewhat easy.

    nate

    --
    55 Commander Starlight
    http://members.cox.net/njnagel

    Leave a comment:


  • bige
    replied
    Unfortunately, if you do all 3 operations, timing, fuel pump and accel pump, all at once you'll never know what the original problem was. It would be a valuable lesson for all involved to know the true solution.

    ErnieR

    Leave a comment:


  • sals54
    replied
    My Holley Blue fuel pump came with a regulator. I took the adjusting screw on the top of the regulator, drilled a hole in it and soldered a short piece of steel tube in it. This allows you to run a hose from the pressure side of the supercharger into the regulator. The regulator will then "read" the higher pressure as atmospheric pressure and deliver fuel at 6 lbs above whatever pressure is being delivered to the regulator.

    sals54

    Leave a comment:


  • edpjr
    replied
    Then do you block off the mechanical pump? If so, what do you do with the line that goes to the super-charger? Who sells the proper electric pump? [?] Thanks.


    quote:Originally posted by JDP

    quote:Originally posted by edpjr

    Indeed, this T-bow kits looks far better and complete. I suspect the top will be coming off the old 4V-AFB again pretty soon for re-work. I've also got a new Carter fuel pump for an R2. If these two items don't get gas flowing properly, I don't know what will. We'll also turn up the timing a few degrees. Wish me luck. [^]

    edp/NC
    '63 Avanti
    '66 Commander
    Electric pump in the rear, most every R2 I've had needed one, the Salt Flats cars had three.

    JDP/Maryland
    edp/NC
    '63 Avanti
    '66 Commander

    Leave a comment:


  • JDP
    replied
    quote:Originally posted by edpjr

    Indeed, this T-bow kits looks far better and complete. I suspect the top will be coming off the old 4V-AFB again pretty soon for re-work. I've also got a new Carter fuel pump for an R2. If these two items don't get gas flowing properly, I don't know what will. We'll also turn up the timing a few degrees. Wish me luck. [^]

    edp/NC
    '63 Avanti
    '66 Commander
    Electric pump in the rear, most every R2 I've had needed one, the Salt Flats cars had three.

    JDP/Maryland

    Leave a comment:


  • edpjr
    replied
    Indeed, this T-bow kits looks far better and complete. I suspect the top will be coming off the old 4V-AFB again pretty soon for re-work. I've also got a new Carter fuel pump for an R2. If these two items don't get gas flowing properly, I don't know what will. We'll also turn up the timing a few degrees. Wish me luck. [^]

    edp/NC
    '63 Avanti
    '66 Commander

    Leave a comment:


  • edpjr
    replied
    Thanks. I ordered a carb kit from Dave Thibeault today. He says it will be complete and better than the other one we used. I sure hope so. My brother says the car is running lean. We'll adjust the timing too. And, if none of these changes fix the problem, I can try the R2 Carter fuel pump I've got that must have originally come from Jon Myer (it has his name on the box). [|)]

    quote:Originally posted by JDP

    quote:Originally posted by edpjr

    My brother doesn't like the way the leather pump fits or works either. The kit I got didn't provide a replacement ball valve. Does anyone know where I can get a different type pump or another R2 carb kit? Thanks! [^]


    quote:Originally posted by wcarroll@outrageous.net

    With respect to the accelerator pump, the leather ones are very difficult to get to work properly and modern gas only seems to exacerbate this.

    If you look at all the new Edelbrocks and Carters you'll see that they use some sort of rubber umbrella/plunger. I went through kit after kit trying to find a leather version that fit well a number of years back. Even tried all the umbrella break-in tricks in the book and still had no luck.

    I wonder if one could adapt a new Edelbrock/Carter plunger to the old carb?

    http://community.webshots.com/user/s...host=community
    edp/NC
    '63 Avanti
    '66 Commander
    Dave TBow has good kits.
    http://www.stude.com/Tbow/

    JDP/Maryland
    edp/NC
    '63 Avanti
    '66 Commander

    Leave a comment:

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