Quote:
The stamped steel cover is pretty thick material, .125 (1/8th thick) if I remember right.
The flat cover was also on some of the early factory pumps, until the factory engineers discovered that it is possible for a small amount of water to collect at the lowest point in the pump, that place is in the pump's impeller cavity, against the flat cover's inner surface.
If that water freezes, the impeller jams and breaks the pump's drive gears.
The cast cover with the "bumps" allow for a small amount of water to settle outside the impeller cavity. The bump openings also helps the oil flow into and out of the impeller cavity a bit better.
DD
Very Interesting. This prompted me to go back and look more closely at what I got. I ordered 2 units for engines I am building in the near future, and a couple of spares.........uh, just because everyone knows how often the pumps go bad The flat cover was also on some of the early factory pumps, until the factory engineers discovered that it is possible for a small amount of water to collect at the lowest point in the pump, that place is in the pump's impeller cavity, against the flat cover's inner surface.
If that water freezes, the impeller jams and breaks the pump's drive gears.
The cast cover with the "bumps" allow for a small amount of water to settle outside the impeller cavity. The bump openings also helps the oil flow into and out of the impeller cavity a bit better.
DD
**dripping sarcasm** 
Anyhow
Everything in a "Clevite" box is marked made in USA, and has the flat stamped steel cover
1 unit was in a "Sealed Power" box, no markings on where it was made, and has the cast cover with the humps in it.
Also 1 unit was in a generic white box, no "made in" markings, Just a P66-C sticker on it. Again with the cast, humped cover.
From what Doc says, guess I'll be using the cast covers first!
CE
Thanks. would have been annoying to have got one then realized 'something is not quite right!'