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  • 351W Pro Flo 4 distributor shaft diameter out of spec?

    I need to change the gear on my Pro Flo 4 351W distributor. The cam grinder specifically says to run an OEM Ford steel gear with my custom steel billet roller cam. The problem is I can't locate a steel gear that fits correctly to get a sufficient press fit. The shaft on the Pro Flo distributor measures .530" OD which is .001" smaller than a factory 351W Ford distributor shaft that measures .531", so all available gears I'm finding won't work. Is this a deliberate design on Edelbrock's part or is it just what the Chinese supplier of the distributor decided to do on their own behalf? I ran into a similar problem with another aftermarket replacement distributor I came across, which is why I'm pretty sure the Pro Flo piece is a Chinese made unit, considering its not an MSD supplied piece even though the box it came in says MSD on the label. I'm disappointed that it looks like I now have to find a custom solution to fix the problem the right way. I understand the gear which is installed on the Pro Flo distributor is melonized, but I'm not comfortable running it despite what is recommended by Edelbrock, being the distributor is already mislabeled and I highly doubt they know exactly which alloy the gear is made from to begin with. Anyone else have this issue?

  • #2
    Answered in the other post, but if you came in to me, I'd likely go with a Crane .500 and machine it, or cross my fingers with the melonized gear, assuming the location was perfect and check in 100 miles. I personally like the Crane option better. I buy a lot of custom cams and I would expect the grinder would be happy with the Crane

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    • #3
      Yes, the .500 gear is an option but the machining needs to be very precise to control runout. I don't have access to a lathe so thats out of the question. The easier solution is to buy a reman 92-97 351W remote mount tfi distributor or MSD 8451 and switch over the pickup from the PF4 distributor. The PF4 pickup is modeled after the OEM Ford remote tfi pickup and mounts exactly like the PF4 in the same cutout. The only difference between the two pickups is the connector and the ground tab, which is missing on the PF4 pickup. I had an extra remote tfi pickup laying around and was able to drop it in place on the PF4 distributor, which even has the ground screw fixing point like the OEM Ford unit. There is a slight difference in electrical characteristics between both pickups, but aside from that both the PF4 and the OEM Ford distributors are the same in fit and function, aside from the PF4 one having the oddball .530 OD shaft.

      So in essence the simplest and cheapest solution to this problem is to run a reman OEM 92-97 351W Ford remote tfi distributor with an OEM steel gear (MSD #435M) and switch over the PF4 pickup, then throw the PF4 piece in the garbage. Its funny that one other guy on here had to run a different gear on his PF4 distributor and edelbrock sent him a free distributor with the correct gear. Im not so lucky.

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      • #4
        What difference have you found in the electrical characteristics between the pickups? I am considering running a factory tfi distributor also. They both should produce a 5V on/off signal, with the ecu triggering off either the rising or falling edge, combined with the smaller shutter wheel tooth for cam position.

        What material is your billet camshaft? The factory steel gear you are chasing will be hardened steel, ie melonized. The crane gear will be the same. Agreed that they are of a known quality, compared to the unknown of the edelbrock distributor, but in theory you are replacing with a gear of basically the same material. I haven't measured my shaft diameter, but I will and report back out of interest. I will say that the gear depth and end play are both setup to spec on my edelbrock unit from the factory.

        Have you modded your oil gallery plugs to spray oil on the distributor gear?

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        • #5
          Regarding the gear situation, I'm not using the supplied gear just because I don't trust its quality. I did a quick hardness test and it doesn't look good. The gear isn't as hard as it should be and it needs to be at least slightly softer than the cam gear to survive.

          The cmp (pip) sensor on a ford runs on 12V while i believe most gm systems use 5V which explains the difference i measure in hall IC specs externally by just bench testing with a scope. The PF4 sensor runs cleanly on 5V while the Ford sensor needs at least 9V to work.

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          • #6
            Originally posted by 408foureye View Post
            Regarding the gear situation, I'm not using the supplied gear just because I don't trust its quality. I did a quick hardness test and it doesn't look good. The gear isn't as hard as it should be and it needs to be at least slightly softer than the cam gear to survive.

            The cmp (pip) sensor on a ford runs on 12V while i believe most gm systems use 5V which explains the difference i measure in hall IC specs externally by just bench testing with a scope. The PF4 sensor runs cleanly on 5V while the Ford sensor needs at least 9V to work.
            Sent you a PM

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            • #7
              OK, so an update on this situation -

              My suspicion was correct. I just unpinned the gear from the distributor and the gear literally slid off the shaft with gravity alone! If I woukd have run the distributor without checking it, the gear would have sheared the pin.

              I guess I'm now stock with a paperweight since I'm out of the warranty period and couldn't get around to installing this system on my car sooner.

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              • #8
                Trying to get through to the tech dept. Getting ahold of anyone is virtually impossible. The phone menu sucks and all you get is put on permanent hold.

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                • #9
                  What size is the roll pin holding the gear on the Edelbrock distributor?
                  At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

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                  • #10
                    Originally posted by BITE_ME View Post
                    What size is the roll pin holding the gear on the Edelbrock distributor?
                    1/8" .125"

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                    • #11
                      Please don't tell me the pin alone is supposed to keep the gear in place and withstand the twisting forces of driving the oil pump. You must have at least a decent press fit to hold that gear - every single functioning SBF distributor I've come across has the gear pressed on with at least .001" interference fit. There's no way a tiny .125" roll pin alone will reliably do the job... not for long at least.

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                      • #12
                        1/8" is the factory size roll pin For performance applications you drill it out to use a 3/16" roll pin. As it is the device used to hold the gear on to the shaft....more later.
                        The pressing of the gear to the shaft, is just to hold it, so you can drill the hole.
                        Slip fit gears are put in a jig to hold the gear in the proper location, so they don't move when drilled at the factory.

                        Back to the roll pins:
                        Ford and other manufacture's have switched to a different "style" of roll pin used to hold the gear in place.
                        It used to be a long rectangle, where the edges butted together....1 layer thick.
                        But with the use of higher volume oil pumps, and some just randomly breaking. The pin is now around 3 layers of rolled sheet metal.....almost making it a solid pin.

                        So.
                        If you really need to change the gear. ( you got to remember that people in other countries read these posts, and most don't have experience in doing certain types of work. Hence why some of my posts are long, and detailed ).
                        Mark on the shaft where the gear is closest to the end of the shaft. Also measure, and wright down this dimension with a magic marker on the distributors body.
                        This will give you the location to place the new gear on the shaft.

                        Now draw a line from one of the holes, up the body of the gear, and up the shaft......this line is in case you find out the work to be done is harder then you thought, and you just want to put the gear back on, and call it a day.

                        Next you punch out the roll pin....use a punch made for this. Don't use some thing pointed like a nail. It will just get stuck in the roll pin. The tool needs a blunt end.

                        If the gear slides off. Nice.
                        If it doesn't slide off. Then use a 2 prong gear puller to pull it off.

                        Next you measure the shaft diameter. This is done on the section of the shaft that the gear is installed at ... basically measure 90 degrees away from the roll pin holes of the shaft.

                        Now you can order a new gear...0.467", 0.500", or 0.531" is basically what Ford gears come in.

                        When you have the gear, you will notice that some have 1 guide hole, and some don't have any guide holes. That's because Ford's gears get randomly installed on the shaft....it's all about end play measurements, and where the bottom of the gear rests on the shaft....that's why you mark the shaft, and measure the location of the gears bottom face ( not the gear part.. you do the gear face....the part of the gear that could touch the block ).

                        If the gear fits tightly. Then you need to press the gear on.
                        Take the cap and rotor off. Put the shaft part that holds the rotor on,, on to a block of wood.....the gear end of the distributor should be pointed up.
                        Use a deep socket, and rubber mallet....other options: Drill press, C-Clamp, jacked up rear/front bumper.....to press the gear on.

                        The one‚Äčone part you have to be carful with. Is you can't reuse the hole that was drilled for the other gear.
                        So you drill the new roll pin hole 90 degrees from the old one.....you mark the new gear where your going to be drilling....if it doesn't have a guide hole.
                        this paragraph should be above the last paragraph. But I haven't learned to cut and paste with this new tablet I bought a couple of weeks ago.

                        Now you drill a 1/8" hole through the guide hole, the shaft, and through the other side of the gear...you really need a drill press, and some blocks of wood to hold the distributor when doing this.
                        Double check to make sure the gear did not move. Then install the guide pin.

                        If the gear did not press fit on to the shaft, or you feel that the gear is going to move during the drilling process. Then use a center punch to raise up a little metal of the shaft, till the friction holds the gear in place so you can drill....if the gear doesn't have a guide hole. Then it's best to drill one on the gear first..

                        So it's not really not that hard to install a different gear on Ford distributors. People just need to measure where the face of the old one rests at, before they take the old one off, and install the new one at the same distance.

                        As for the Melonized gear. melon is defined as black. Ized is just a generic term to mean it had a process done to it.
                        Lots of OEM motors use Melonized ( or recommend ) gears on billet camshaft motors.
                        And just like how you need to retorque bolts on a motor. It's a common practice to inspect distributor gears after use, and installing a new gear with every camshaft change.
                        At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

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                        • #13
                          Originally posted by 408foureye View Post
                          Please don't tell me the pin alone is supposed to keep the gear in place and withstand the twisting forces of driving the oil pump. You must have at least a decent press fit to hold that gear - every single functioning SBF distributor I've come across has the gear pressed on with at least .001" interference fit. There's no way a tiny .125" roll pin alone will reliably do the job... not for long at least.
                          Yes. The roll pin 100% holds the gear on. Seriously this is 100% none debatable in any way.
                          At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

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                          • #14
                            Originally posted by 408foureye View Post
                            Trying to get through to the tech dept. Getting ahold of anyone is virtually impossible. The phone menu sucks and all you get is put on permanent hold.
                            You can email your photos to [email protected]

                            Calling into the TechLine gets priority 800-416-8628

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                            • #15
                              Wait a second, I thought BITEME had left the building.

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