Fuel pump eccentric the same for a 390 as a 302?

Discussion in 'Technical' started by Ryan, Dec 18, 2011.

  1. Ryan

    Ryan Ford Addict

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    I have an HO roller block with no fuel pump eccentric on front of the cam for the mechanical fuel pump. I dug around at my dads house and found 4 eccentrics. 3 are one piece and 1 was the outer piece of a 2 piece eccentric. I know the one piece eccentrics were out of 390 motors. Anybody know if they are the same size as the 302 eccentrics?
  2. FordsForever

    FordsForever Member

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    One and two piece eccentrics are both used in a 289/302. Same size OD. Don't know if they are the same size as Big blocks.

    R
  3. baddad457

    baddad457 Member

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    390's used a different eccentric, all were one piece. 302's used both one and two piece eccentrics.
  4. Ryan

    Ryan Ford Addict

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    Whats different between the 302 and 390 pump eccentrics? I cant find any specs anywhere saying what the sizes are.

    Does anybody have a 302 eccentric laying around that they can measure? The one I have could be from a 302 or FE block but not sure. As long as its the same size it should work. So can somebody measure the total outside diameter? And the offset of the bolt hole?
  5. baddad457

    baddad457 Member

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    I have several one piece eccentrics, I coulda swore the 390's were bigger, but they're not. But they are thinner than the small block 1 pc. The small block 1 pc. eccentrics are 1" thick x 2-1/2" dia. The two piece are 7/8" thick. The 390 eccentrics I have are 3/4" thick. Bolt pattern is the same for all.
    Last edited: Dec 26, 2011
  6. FordsForever

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    The eccentric for a SBF is 2.513" X .945" whether 1 piece or 2 piece. Later engines use a 3/8" bolt. I think some earlier engines may have used a 5/16" bolt but not sure on that. Be aware that the eccentric dowel uses two different length pins. A 1 piece eccentric uses a dowel 1 3/8" long. A 2 piece has a shorter pin at 1 1/8" long.

    Have no dimensional specs on a big block.

    RS
  7. Ryan

    Ryan Ford Addict

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    Sounds like they may be interchangeable. If you look at the wear patternd do you think the thinner one would be a problem?

    Mine has a 3/8" bolt going through it, need to check the 390 eccentric and see what it has. Forgot to do that before closing up the garage.
  8. baddad457

    baddad457 Member

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    None of the 1 piece show much sign of a wear pattern and there's only a 1/4" difference in width. 390's also used a 3/8" cam bolt, same as the small blocks. The 390 spacer could be the fix for using a later timing cover that's got less inside room. You can always mock it up and look thru the fuel pump hole to see how it fits before installing the pump.
  9. Ryan

    Ryan Ford Addict

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    It sounds like what I have just might do the trick. bolt size works with my cam, the outside diameters and the same, and the 302 ones were all the same thickness anyways so this one should be thick enough. Now if I could just get the dowel pin out of the cam so I can put in the longer one.
  10. FordsForever

    FordsForever Member

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    If the dowel pin you are trying to remove is the shorter one then it must have had a 2 piece eccentric at one time. The pin can be stubborn to get out. I had to use a pair of vice grips to get one out once. Buggered up the end a little bit. But wasn't plan on reusing it so didn't really matter. Try a hitting it with some penetrating fluid for awhile before trying to remove it. Might loosen it up some. Even try a little heat on the cam end to expand the metal a little bit too.

    RS

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