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  • who is are holley experts? I got a 780 question

    Im not sure if it started life as a 780, it has jets and power valves
    at both ends, center hung float bowls, and 4 idle screws, NO
    rear acc. pump (so wasnt a double pumper), and a place for the vac. diaphram, the choke horn
    has these numbers 3310-3 2818. Also what would be jets, and
    power valves the 780 would come with? this carb isnt complete
    but I need something to run on my 350 and later on my 406, thanks
    cobey/om71
    COBEY..... franklin, kansas

  • #2
    Re: who is are holley experts? I got a 780 question

    72 jets in front with a 65 power valve, 134-21 metering plate originally in back, it's a 750 cfm not 780.

    My fabulous web page

    "If it don't go, chrome it!" --Stroker McGurk

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    • #3
      Re: who is are holley experts? I got a 780 question

      Somebody pieced that together. 3310-3 is the third version of the common 750/780 vacuum secondary carb. It would have originally had a metering plate in the back with fixed jetting, instead of a metering block that accepts screw in jets, and the vac. secondary carbs never had a rear idle circuit. Sounds like someone may have stuck a primary block on the rear.

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      • #4
        Re: who is are holley experts? I got a 780 question

        will it work with the front primary block in the back?
        what would the 780 have had? will this do weird
        stuff or give me a more versetile carb?
        thanks Jim and Kris , I like to start with an unmolested
        core but times are tough.
        COBEY..... franklin, kansas

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        • #5
          Re: who is are holley experts? I got a 780 question

          I think the early versions of that carb were marketed as a 780 even though they all flow the same. I don't know if the primary block would work in the rear but I doubt it, and I wouldn't mess with it. I have a stock metering plate for it you can have to get it going, and you can still buy the rear metering block conversion kit for it-they used to be pretty cheap, don't know now. I have some extra parts for those down at the shop-I'll see what I have and call you next time I'm down there. I love those carbs-you can make them work on almost anything pretty well.

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          • #6
            Re: who is are holley experts? I got a 780 question

            3310 (with no dash number) and 3310-1 are the 780's. The 780 carbs also feature drop-leg boosters. I have two of 'em in the garage.

            I just tried uploading some pics showing the difference between straight-leg and drop-leg boosters and my photobucket account is doing goofy stuff... alas, no pics.

            The 3310-1 is pretty much the same as the 3310 but it has a large vacuum port (for power brakes) on the base plate.


            Ron

            edit: I suppose the front metering block would work on the rear, but remember, the front block has idle mixture screws. The rear of your base plate won't be machined to make use of the idle mixture feature on the rear, so you will need to block off the idle mixture passages in the metering block.

            I like the 780 series carb for the simple reason of added adjustability with a secondary power valve and secondary jetting. I used to NOT like Holley carbs until I got ahold of one of the 780's.
            It's really no different than trying to glue them back on after she has her way.

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            • #7
              Re: who is are holley experts? I got a 780 question

              Originally posted by Mr4Speed
              I think the early versions of that carb were marketed as a 780 even though they all flow the same. I don't know if the primary block would work in the rear but I doubt it, and I wouldn't mess with it. I have a stock metering plate for it you can have to get it going, and you can still buy the rear metering block conversion kit for it-they used to be pretty cheap, don't know now. I have some extra parts for those down at the shop-I'll see what I have and call you next time I'm down there. I love those carbs-you can make them work on almost anything pretty well.
              thanks kris Ill call you soon, thanks to Ron also

              COBEY..... franklin, kansas

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              • #8
                Re: who is are holley experts? I got a 780 question

                I just took the back bowl off they tryed to run it
                with NO power valve :P i bet it ran real good!!!!
                there is no room on the main body for the power valve
                (just flat, missing the recess) so you have to use the metering plate
                for sure!!
                COBEY..... franklin, kansas

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                • #9
                  Re: who is are holley experts? I got a 780 question

                  Holley sells a conversion kit to remove the metering plate on 3310's and add the metering block. Part #34-13 for the 3310.

                  If the metering block on the rear of that 780 has a power valve hole, it's a primary metering block someone added. The idle screws have me thinking that.
                  BS'er formally known as Rebeldryver

                  Resident Instigator

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                  • #10
                    Re: who is are holley experts? I got a 780 question

                    I'm pretty sure that the conversion rear blocks don't use a power valve. The metering blocks usually have a list number stamped in them-see if it does and you can tell what it's off of.

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                    • #11
                      Re: who is are holley experts? I got a 780 question

                      I have done this quite a few times, and have two of them right now. You can use either type of metering block, and they make a solid plug style power valve that fills the hole nicely. You'll have to use four primary side float bowl screws too.
                      Originally posted by TC
                      also boost will make the cam act smaller

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                      • #12
                        Re: who is are holley experts? I got a 780 question

                        thanks alot for the replys guys, anyone know who (jegs, summit, ect ect)

                        sells that metering block kit or can I get it directly from holley?

                        the primary block, that they were useing on the rear, has the #7089 & #1601

                        on it.
                        COBEY..... franklin, kansas

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                        • #13
                          Re: who is are holley experts? I got a 780 question

                          http://www.summitracing.com/parts/HLY-34-13/

                          if Scott's part number is right

                          My fabulous web page

                          "If it don't go, chrome it!" --Stroker McGurk

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                          • #14
                            Re: who is are holley experts? I got a 780 question

                            Originally posted by squirrel
                            http://www.summitracing.com/parts/HLY-34-13/

                            if Scott's part number is right

                            No faith............
                            BS'er formally known as Rebeldryver

                            Resident Instigator

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                            • #15
                              Re: who is are holley experts? I got a 780 question

                              I assume it's right, just passing along the credit where due
                              My fabulous web page

                              "If it don't go, chrome it!" --Stroker McGurk

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