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Thread: Fuel pump eccentric confusion

  1. #1
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    Fuel pump eccentric confusion

    Hi Guys,

    So I am finding a lot of contradicting information and would really like to figure this out. I am converting an explorer motor to a carb and had ordered all my parts from Mike Forte (who is absolutely fantastic to work with!!). I have a installed the double roller timing chain and two piece fuel eccentric. I am using the shorter dowel pin, which is correct. However, I notice that the outer part of piece of the eccentric does not rotate freely around the center piece.

    Is the outer piece supposed to rotate around the center one? I have already installed the timing cover and water pump. I really hope I don't need to remove everything. But I can't imagine that a two piece wouldn't work differently than the one piece.

    I also noticed that when the eccentric is installed, there is a 1/32 of an inch wobble to it.

    Any help is appreciated.

  2. #2
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    The wobble is normal. Try dipping the whole thing in motor oil and see if it will turn more freely. I am not going to say everything is right without actually handling the part, but it does not sound like an issue.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

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    Hey thanks for the response. I'll just have to pull the timing cover and see how much force it takes to spin as well

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    Ok. So I just pulled the timing cover and found something interesting. The center of the eccentric looks like it was damaged from torquing it down. You can see the hairline crack below. it looks like the outer piece of the eccentric is up against the cam gear and is causing the inner piece to bend (as shown) when torqued down.
    IMG_1339.JPG
    IMG_1338.JPG
    IMG_1337.JPG

  5. #5
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    I wonder if I can just shim the it with a thin washer. Or do I need a different cam gear? Either way, looks like I need a new eccentric.

  6. #6
    Senior Member CraigS's Avatar
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    That contact mark at just below 3 oclock in the first pic looks like a clue. But they both have the same crack. I am not sure I understand how they are supposed to fit together though since I have never used a 2 piece. Pitch them and get a one piece? But also need to figure out why the mark which may tell you why there is a wobble also. Is the gear properly seated on the cam? Does it wobble also? A wobble at the gear should be fairly obvious due to the larger diameter. On the face of the cam gear at about 2 oclock I see a small imperfection right at the edge of the smooth surface. Is that significant? Does it match the position of the wear mark on the eccentric? Sorry, lots of thinking out loud but not much of a solution.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    Quote Originally Posted by CraigS View Post
    That contact mark at just below 3 oclock in the first pic looks like a clue. But they both have the same crack. I am not sure I understand how they are supposed to fit together though since I have never used a 2 piece. Pitch them and get a one piece? But also need to figure out why the mark which may tell you why there is a wobble also. Is the gear properly seated on the cam? Does it wobble also? A wobble at the gear should be fairly obvious due to the larger diameter. On the face of the cam gear at about 2 oclock I see a small imperfection right at the edge of the smooth surface. Is that significant? Does it match the position of the wear mark on the eccentric? Sorry, lots of thinking out loud but not much of a solution.
    Hi Craig. No the gear does not wobble. The contact mark in the first picture is from me messing with it trying to spin it as I tightened the cam bolt. I was doing this to see when it was binding up. I switch to a one piece, I need to remove the cam dowel and replace it with a longer one. I also need to make sure there isn't any interference with the timing cover, since I have read that the one piece is "taller".

  8. #8
    Senior Member CraigS's Avatar
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    I checked my 408 stuff but turns out I used a Comp Cams 3230 chain set which is single row so I can't help w/ whether it will fit w/ yours. I used this one piece eccentric
    https://www.summitracing.com/parts/fms-m-6287-b302
    You can get one and measure to compare to the two piece. It's a little hard to understand why it would be taller but who knows.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  9. #9
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    UPDATE:

    Spoke with Mike and sent some pictures. He is the man and getting this resolved. Outstanding customer service!

  10. #10
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    Maybe it's hidden by the camshaft bolt in your picture but, I don't see the hole in the timing gear that the tab on the fuel pump eccentric is supposed to fit into. That locks the eccentric onto the gear so it has to turn with the camshaft and drive the fuel pump arm up and down. Here is a picture I borrowed off a Google search.

    HTH

    Norm
    Attached Images Attached Images

  11. #11
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    Quote Originally Posted by Norm B View Post
    Maybe it's hidden by the camshaft bolt in your picture but, I don't see the hole in the timing gear that the tab on the fuel pump eccentric is supposed to fit into. That locks the eccentric onto the gear so it has to turn with the camshaft and drive the fuel pump arm up and down. Here is a picture I borrowed off a Google search.

    HTH

    Norm
    It's in there. just hidden by washer/bolt

  12. #12
    Senior Member CraigS's Avatar
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    Dang Scott, go to bed! ha, ha.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  13. #13
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    Quote Originally Posted by CraigS View Post
    Dang Scott, go to bed! ha, ha.
    hahaha couldn't sleep. motor was keeping me up!

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