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Thread: M8 Greyhound help

  1. #11
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    Perfectly normal to have different shims or bearings to get best clearances. On any equipment that will see severe angles while in operation will have several pickup points to keep oil at the pickup. Also later on baffles or directional oil pan doorways are used to keep oil going to the pump also.

    Motorsports engines use the same type systems, and even today ordinary production cars and trucks are also.
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  3. #12
    Moderator WillWagner's Avatar
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    It is basically 2 separate pumps. The main P/U in the sump pulls the lube oil and supplies the engine oil pressure. The scavenging system, when in high angular operation, pulls the oil from what is the front, but would be the rear of the vehicle and discharges it into the sump. The scavenging part is what had me going because it was unknown to me at first what it was. After boning up, it is clear as day how it works. I THOUGHT the pump pulled from all 3 ports and was unable to reason WHY/HOW it work like that because all that would happen would be that the pump would only pull air. I know the engine had OP, I dove it 15 or so years ago after getting it running, and stopping.

    As for the shims, the parts and engine manuals indeed show shims on both rods and mains, but, it calls for 2, .003 in shims per side. The shims are hand made on this engine, .010 on one side, .015 on the other. I put it back together using the shims that came out of it and but them back in the same spot. It has end play, so I am not worried about that part. I know babbit bearing engines needed shims, I had never seen shims used on a modern tabbed type bearing, but, since this was made in the 40's, maybe it is a transition thing?
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  5. #13
    4 Star General NDT's Avatar
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    Yes, the Hercules engines are 1920’s designs, and precision bearing halves were not yet invented. Rebuilding a Hercules engine, specifically setting up the crankshaft clearances, is an all day thing using trial and error with shims and lots of plastigauge.

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