Oil drain back holes vs. Tomahawk deck.

Discussion in 'Race 400/430/455' started by GS Kubisch, Apr 19, 2017.

  1. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Mocking up my engine and the drain back holes in the cylinder head land right on the deck.

    This would lead me to believe that the ones out there running are filling up the valve covers and
    draining back through the pushrod holes ??

    Or ... Did you notch/chamfer the deck to allow the heads to drain through the intended holes?

    This would also necessitate a notch in the head gasket.
  2. Jim Weise

    Jim Weise GOT AIR? Staff Member


    Look carefully, and you will see that there is a vertical space between the bottom of the oil drainback hole, and the block. It's deceiving just looking at it from the top.

    Take a look here


    Oil drainback holes are the ones on either ends, next to the pushrod holes. They are in a recessed area of the casting, so they don't seal against the head gasket.

    With this engine, there is no reason to have a full valve cover. Oil volume should either be controlled by your lifters, pushrod oil hole restrictors, or the jet restrictors in the block oiling system. With priority main oiling, we no longer are required to run full pressure/volume main galleys, although I do perfer to install -6AN o ring plugs in the oil manifold, and control the oil to the heads with lifters and pushrods.

    Last edited: Apr 19, 2017
  3. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Makes sense Jim, Thanks.

    I have a block here and a head gasket marked for trimming but my heads are elsewhere. That clears it up though. Thanks again.
  4. BP_Motorworks

    BP_Motorworks Ragtop Racer

    All the heads I have worked on that were built by major names have -6 drain backs in the back of the head that run to the oil pan. It wouldn't be a bad idea to add those.
    GS Kubisch likes this.
  5. Robs455

    Robs455 Well-Known Member

    Can anyone explain further the TA Block oil flow path?
    I was guessing, from the pump it goes through all mains and in the back of the block it goes up through the o-ring "jet" fittings.
    From there it flows in both lifter gallery and with a small hole in the lifters & pushrods up to the rockers.
  6. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    I'm considering doing this.

    That's what I thought.
  7. Jim Weise

    Jim Weise GOT AIR? Staff Member

    We have a new main galley now. The RH lifter galley no longer feeds the mains.

    Pump, main galley, oil manifold on the rear, lifter galleys is the oil flow path.

    I will be building another one next week, and will take some pics.

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