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Holley Carb - Running too rich

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  • Fuel System: Holley Carb - Running too rich

    The 62 GT I bought last summer came equipped with a Holley O-8007 390 CFM carb. It idles and runs so rich that I have black soot blowing out the tail pipes, can be seen in the photo;
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ID:	1750877 Before I knew this was a 350 CFM carb I assumed it might be over carburated but this carb should be suitable for a 289. I wanted to see if the floats were set correctly but where there would normally be a screw on each bowl to remove and see if the fuel is coming out there is instead a clear sight tube. I can't tell if the fuel is there or not and I don't know if it's wise to try and remove them? (last photo) The car starts perfectly but idles as if it has a slight cam, it never stalls and actually runs good and has good acceleration but uses a lot of fuel. With the car in park and revving up to 2500 or 3000 rpm it sputters and does not run smoothly but like I said on the road with a load on it seems fine. I have had it suggested by some wise Stude types in my area that I would be far better off with and Edelbrock 1403 500 CFM carb. I'm trying to decide whether this could be something other than carb, whether to not bother messing with the Holley and get the Edelbrock and sell the Holley, or to try and see if this carb can be tuned to work? There is a spacer plate in place here and an aftermarket intake so I think the Edelbrock should be an easy install? Any advice would be appreciated.
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ID:	1750881PS.. the idle mixture has already been leaned out as much as possible but no jets have been replaced.

  • #2
    That looks like a Holley 4150, with vacuum operated secondaries. An excellent carb, but impossible to tell if it is a 390 cfm, it could be as large as an 850 cfm. Also, impossible to tell which jets are in it, without dis-assembly. It is much more sophisticated than the AFB clones, around today, which are 1950s-60s technology.

    I'd get a good Holley manual; educate myself on the cfm sizes and jets, then determine what that one is. If it is a 390, I'd dis-assemble and install components compatible with a 289, then give it a try. As is, it sounds like a pig in a poke.

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    • #3
      Originally posted by JoeHall View Post
      That looks like a Holley 4150, with vacuum operated secondaries. An excellent carb, but impossible to tell if it is a 390 cfm, it could be as large as an 850 cfm. Also, impossible to tell which jets are in it, without dis-assembly. It is much more sophisticated than the AFB clones, around today, which are 1950s-60s technology.

      I'd get a good Holley manual; educate myself on the cfm sizes and jets, then determine what that one is. If it is a 390, I'd dis-assemble and install components compatible with a 289, then give it a try. As is, it sounds like a pig in a poke.
      When I enter the 8007 number that is stamped on the carb on the Holley web site it always shows as a 350 CFM but I agree visually it looks identical to the 4150. It would seem this carb should be the right fit for a 289 but I'm going to have to figure out this rich running. Like I said, I wanted to start with the float settings. With many Holleys you simply take the screw out where there are sight gauges on my carb and since I have an electric fuel pump, with the screws out, turning the pump on should not cause fuel to flow out. If it does the float needs to be lowered. As I read it the correct setting is set when by rocking the car a little bit of gas comes out. Problem with this one is I am afraid to try and remove the plastic sight gauges for fear of breaking them and I can't tell if the fuel is at the right level or not.

      Comment


      • #4
        Probably popped the power valve...
        HTIH (Hope The Info Helps)

        Jeff


        Get your facts first, and then you can distort them as much as you please. Mark Twain



        Note: SDC# 070190 (and earlier...)

        Comment


        • #5
          Originally posted by DEEPNHOCK View Post
          Probably popped the power valve...
          Yes, that was one of the other suggested causes on the Holley sight.

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          • #6
            First...it's NOT a 4150, it's a 4160..!
            The 4150 has never had a single feed design as this one does. So to add...no way it could never be a 850 either, at least not from the factory..!

            As for the possible problems (some have been mentioned) -
            1. Too high a fuel pressure, (possibly).
            2. Too high a float level, (possibly).
            3. Mixtures screws not adjusted correctly.
            4. Choke cam sticking partially closed.
            5. Too much jet, both primary and secondary, (possibly). NOTE: the secondary is an internal "plate" that takes the place of actual jets.
            6. Leaking power valve, (possibly).
            7. Incorrect power valve opening value for the vacuum available, (likely).
            8. The main body could be warped where the jet plate is attached leaking fuel. While not likely warped enough to cause your problem, the careful use of a clean Mill file will prove or disprove this one.

            OR, any combination of the above.
            While I prefer the Holley to the Edelbrock/AFB for power, normally the Edelbrock will get slightly better mileage if that is a concern.

            Mike

            Comment


            • #7
              Call Holley Tech Support. The Holley's are infinitely adjustable, and when done right are EXCELLENT runners...

              Comment


              • #8
                Originally posted by 345 DeSoto View Post
                Call Holley Tech Support. The Holley's are infinitely adjustable, and when done right are EXCELLENT runners...
                I agree, they are excellent runners. Have ran Holey 4360 carbs on Studes for many years, and still have one on the 56J. I have removed and shelved more AFBs and AFB clones than I care to remember. I have yet to see an AFB or clone that gets better MPG than a tuned 4360. As for the ones on the shelf, I hear aluminum prices are going up

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                • #9
                  All of Mike's list are the things to look at. One good back fire up the carb likes to take out the power valve.

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                  • #10
                    Originally posted by JoeHall View Post
                    Hello Joe.....
                    A while back you mentioned the Facet pumps (high pressure) you employ on your 56J with the return fuel line. What was the number again?

                    thx
                    64 GT Hawk (K7)
                    1970 Avanti (R3)

                    Comment


                    • #11
                      As suggested by others, good chance the power valve is the culprit. One backfire can take them out, and they get old and fragile. Consider the other suggestions, problem solve, to a solution. There are "blow proof" power valves on the market. tempestan

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                      • #12
                        Originally posted by 64V-K7 View Post
                        A while back you mentioned the Facet pumps (high pressure) you employ on your 56J with the return fuel line. What was the number again?

                        thx
                        Hi Bob,
                        I had forgotten your email. Definitely was not ignoring you. You mentioned Facet #40270, and that sounds right, but I cannot recall for sure. I looked on ebay, and could not find any by that number. Purolator also makes the same pump. I recall it was higher PSI and higher GPM than most of them, and also would vertically draw fuel 18-30 inches IIRC. I always mount the electric pump on the front gravel shield, and was running a return line, so this pump seemed like the best fit for my needs. It has not disappointed one bit. I just drove the car 665 miles round trip to SB, and it ran like a 56J. I have ran those cube type pumps for many years without issue, but that one is a little higher capacity, which seems to work best with a return line. You still need to restrict the return line though; mine is restricted about .062", I believe.
                        Sorry, not tryin to hi jack this thread. Will shut up now.

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                        • #13
                          Thanks all for the comments and suggestions. I am definitely going to start with the power valve. Going to get a good vacuum gauge tomorrow and see if it is the correct valve for the vacuum level on this car. If that doesn't do it I'll move on to the other possibilities on the list but I think I will definitely try and make this carb work. Other than the rough idle this car performs well so looking forward to getting it tuned up properly. Thanks again!

                          Comment


                          • #14
                            You can different rated power valves, the trick is to get one that suits your driving style. drain float bowl and remove, when metering block is removed watch for fuel in cavity that should be dry, that's open to manifold vacuum and is where power valve resides. also power valve has vacuum rating stamped in edge of brass portion of stem that looks like small nut. Good Luck, Doofus

                            Comment


                            • #15
                              Originally posted by doofus View Post
                              You can different rated power valves, the trick is to get one that suits your driving style. drain float bowl and remove, when metering block is removed watch for fuel in cavity that should be dry, that's open to manifold vacuum and is where power valve resides. also power valve has vacuum rating stamped in edge of brass portion of stem that looks like small nut. Good Luck, Doofus
                              Yes, as I understand it the number on the valve should be half of the measured vacuum at idle. The valves are rated at 1/2 levels so 11 psi would require a 5.5 valve and 12 psi would also require a 5.5 as there is no 6.0 and you always go one level lower. A 6.5 would be too high. Think I have it right!

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