Oil Pump Bottom Plate Gasket

[TinCup]

Recently while working on an oil pump for a motor I am working on, one of my buddies told me that I didn't need the bottom gasket on the oil pump. A prominent engine builder in the area told him that it wasn't needed and actually diminished it's performance. Now I am pretty sure that old Henry wouldn't have put it there it wasn't needed. So what would be the advantage of leaving this gasket out.

[Purdy Swoft]

I don't use the bottom gasket. I'm not sure if Henry originally used the lower gasket. It could be used as a shim if the pump gears were too long and rubbing the bottom, even so it would diminish pump action. There was a good artical in one of the early secrets of speed journal. Reduceing the area inside the pump increases the action. I always use the top gasket under the screen shroud part of the pump. I avoid the earlier pumps with the shroud soldered in place.

[Russ/40]

I suspect that is true, IF, you are using an original plate, since there would be wear on the plate. Eliminating the gasket would possibly restore the tolerances. Personally, I would rebuild the pump, use the gasket, and just flip over the plate.

[James Rogers]

I agree with Purdy

[John Stone]

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Here is what I have found. Some oil pumps don't require the gasket and some do even though the plate is flat. I put the pump together and see how it turns. If it binds, I put the gasket in, if not, I leave it out. If you put it in and it still binds, it is due to the gears not contacting correctly. The only kits that I have found that mesh correctly 100% of the time is Melling.