Now that I have an OHV 6 pump to compare to the flathead pump, here are pictures to show the differences.
here was a write up I found some time back, but can't find the link--
"Oiling System
As the number of areas requiring lubrication in an engine increases, so must oil-pump capacity. The oil pump for the OHV straight-six was redesigned employing several ideas which had only been used previously on experimental engines.
The new oil pump had the cover and gasket eliminated, and powdered metal spur-tooth gears were substituted for the then commonly used helical cut-steel gears. Elimination of the cover was made possible by inverting the pump body so the cylinder block acted as the cover.
These changes impacted pump capacity as indicated by oil pressure. It was now also possible to shorten the gear and pump body length with the new style design and still enjoy an increased capacity.
During preliminary testing no problems developed with the new design, but several of the first pilot engines suffered from seizure because of an issue with the oil pump drive shaft. This was due to assembly concerns in obtaining the proper alignment of the driveshaft bearing in the pump body with the bearing in the engine block. Once the alignment was brought into specification, the problem was eliminated.
Another design correction was the placement of the "C" washer which positioned the driving shaft gear with respect to the camshaft. Initially, this hardened washer was located in a recess in the engine block where it rotated with the shaft and with respect to the block. Occasionally sharp corners and edges on the "C" washer enlarged the block recess and destroyed the relationship of the cam drive gear and the oil pump driving-shaft gear. This resulted in an increased wear factor of these parts.
The solution was found by transferring the "C" washer recess from the block to the end of the gear. In this location there was no relative motion between the gear and the "C" washer; both rotated together and allowed for no wear."
here was a write up I found some time back, but can't find the link--
"Oiling System
As the number of areas requiring lubrication in an engine increases, so must oil-pump capacity. The oil pump for the OHV straight-six was redesigned employing several ideas which had only been used previously on experimental engines.
The new oil pump had the cover and gasket eliminated, and powdered metal spur-tooth gears were substituted for the then commonly used helical cut-steel gears. Elimination of the cover was made possible by inverting the pump body so the cylinder block acted as the cover.
These changes impacted pump capacity as indicated by oil pressure. It was now also possible to shorten the gear and pump body length with the new style design and still enjoy an increased capacity.
During preliminary testing no problems developed with the new design, but several of the first pilot engines suffered from seizure because of an issue with the oil pump drive shaft. This was due to assembly concerns in obtaining the proper alignment of the driveshaft bearing in the pump body with the bearing in the engine block. Once the alignment was brought into specification, the problem was eliminated.
Another design correction was the placement of the "C" washer which positioned the driving shaft gear with respect to the camshaft. Initially, this hardened washer was located in a recess in the engine block where it rotated with the shaft and with respect to the block. Occasionally sharp corners and edges on the "C" washer enlarged the block recess and destroyed the relationship of the cam drive gear and the oil pump driving-shaft gear. This resulted in an increased wear factor of these parts.
The solution was found by transferring the "C" washer recess from the block to the end of the gear. In this location there was no relative motion between the gear and the "C" washer; both rotated together and allowed for no wear."
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