Oil Pump Porting: Part 1

The F23 oil pumps don't have a bad reputation (that I'm aware of) like some of the other Honda single cam 4cyls do. Even the ones that do carry a bad rep. aren't necessarily all that bad under normal conditions. It's when they are asked to keep up with modified engines and spirited driving that they seem to fall short and starve the engine of precious lubricant.

I have been inspired though by this thread over at Onecamonly.com. It details the improvements needed to prep a D16 oil pump for reliable high-performance use. At first I only wanted to compare the internals of my pump with those of the D16. When I did I found areas that could be better optimized even if it wasn't really required for adequate flow I decided to give it a shot.

Once the pump is off and flipped face down on the work bench you can see the plate that incloses the pump itself. 8 bolts hold it in place. The black flat head socket screws replaced the factory polished/plated Philips head screws. The replacements are ISO 10.9 which I understand to be grade 8 equivalent. As used in the forum post linked above I made the switch to help with retorquing the bolts at final assembly.

With the cover off we can see it's a trochoid gear pump.

With the cover off we can see it's a trochoid gear pump. The oil is drawn in from the sump pickup tube (top of image), passes through the gear and into the outlet passage (toward lower right corner). The vertical cylinder to the right of the gear is the pressure relief valve. It intersects the outlet passage and contains a spring loaded piston. As the pressure leaving the pump rises with increasing crank RPM the piston is forced beyond the two ports in the cylinder and flows back to the inlet of the pump. Shims (washers..) can be added or a stiffer spring installed to boost the pressure if one so desired.

 

A close up of the inlet port. A sharp edge for sure. Although with the oil moving into a larger space rounding and smoothing will have little effect. I messed with it anyway...

And here is the outlet port. Plenty of room to improve. 

So far I've done some radiusing of the edge. I'm not yet done with this area. I'll probably add some aluminum filled epoxy to the odd cavity in the "floor" and the corners to better transition from square cross-section to circular. 

This is the turn into the block. The spur section with the threaded plug will be filled with epoxy and then smoothed. The short side radius will also be reworked a little.

It's hard however to get a shot of that area. I'll keep working on that..

As soon as I get the aluminum filled epoxy I can get this pump housing finished. Check back soon for Part 2 where I'll finish this thing up and mount it up to the block.