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Flat head engine oil pump problem

Discussion in 'The Hokey Ass Message Board' started by Digger_Dave, Dec 14, 2012.

  1. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Member Emeritus

    Putting the finishing touches on the new flat head. All rotating assemblies are in place. (crank, rods and pistons)

    Pulled the new MCF full flow oil pump (a new Melling - short body) out of the box; and tried to put it into position.

    Two problems came into play. (this is if it was mounted in its correct position)

    1. The pressure relief "nut" (on the side of the pump) interferes with the rear main bearing cap reinforcement strap.

    2. The oil pan pickup opening (on the pump) won't allow us to bolt the pickup on without running into the rear crank counter weight.

    If we rotate the entire oil pump clockwise slightly, we can get the clearances we need; BUT then the pump mounting bolt hole will NOT line up! PLUS; we would need to modify the side of the oil pan.

    One thought we have is to machine off the existing mounting tab; and using a piece of 3/16 plate, fabricate and weld a new tab in position.

    A second thought was to use a "long body Ford" pump and retrofit the MCF parts.

    Anyone else run into this before?? (and would our solution(s) work?)
  2. Depending on how much you need to relieve the strap Dave. Minimal clearance of a strap will not weaken it all that much. Think smooth relief, no sharp edges or cuts.

    Can you use a " Button head socket head cap screw " on the P/U? I posted a pic if you don't know what one is.

    Pics would help greatly.


    Attached Files:

  3. flatjack
    Joined: Feb 13, 2007
    Posts: 948


    What kind of crank? Also what is the rear strap? Any pictures?
  4. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Member Emeritus

    TR, thanks for the reply.
    The problem with the strap is that the cap and bar is held in place with ARP long studs, a stack of hardened washers and an ARP nut. To relieve the strap for the clearance needed would cut into the hardened washers.

    For the pickup; using "Buttoned Head cap screws (I use them a lot) wouldn't solve the misalignment problem. In stock (for the MCF) position, the opening for the pickup on the pump, is what is causing the grief. Even with a modified pickup tube, it still won't clear the crank.

    I'll try to add pictures as soon as I can.

  5. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,517

    Member Emeritus

    flatjack, the crank is a Merc 4" set in a C69A block (Canadian equivalent of a 59A USA manufactured engine)

    The strap is made from high tensile steel that bridges the rear main cap bolts.
    A small flat has been milled on the top of the cap so the strap sits tight to the cap without a center bolt.

    The top of the cap bolt surfaces are spot faced so that the top of a stack of hardened washers (ARP's) is exactly even with the flat on the top of the cap.

    The hardened washers are slightly larger in diameter than the stock nuts; so the spot facing was made slightly larger to clear. The spot facing on the cap bolt surfaces only took about .060 to get the right height combination. (cap + washers to underside of strap)

    It was interesting to note that the ARP hardened washers only varied .00002 inch in thickness.

    428 Ford main cap studs (normally used with a girdle) allows the studs to be screwed further into the block and stick up enough to pass through the cap, the hardened spacer washers, the reinforcement bar, another hardened washer, and finally an ARP nut.

    Trying to relieve (clearance) the main cap reinforcement bar would mean a lot of tricky grinding. (plus the engine is assembled)

    The oil pickup tube sticks straight into the rear crank counterweight.
    So short of repositioning the pump slightly, I'm looking for an easier fix!

    Thanks for hearing me out!

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