The stock HCI oil pump is a two section pump with very small sections. Since my engine has pressure fed lifter bores and knuckle pins it seemed prudent to increase the oil pumps abilities.
The design was based on Chevy 350 oil pump gears which are 1.2" tall. The oil pumps were bought at the local Autozone for 13.99 each! All that was needed were the gears but it was nice to study the pump design even though it was meant for wet service. Since leakage is not permissible on my "out of doors" pump O-ringed sections would have to be used. The tolerances for the remanufactured Chevy pump were very sloppy however the gears were almost identical from pump to pump. (+/-.0003) Determining the gear center to center distance was easy but determining the bore dimensions required that I make a test pump section.
Where possible, the pump sections were bored together for perfect final alignment. Even so, things were a hair off requiring a loosening of the gear bore with a dingleberry hone. Seems at .001" clearance I had made the tolerances a bit too tight. For the O-ring recesses I used a full radius insert in a mini systems toolholder. The inserts are expensive but well worth it. I also used them on the crankshaft for undercutting threads.
After a little research on AN plumbing I really wanted to use an SAE O-ring boss for the pump section ports. Making the tapered port which the O-ring nests in would have been possible on a lathe but would have taken a while to set up. The simple answer was to purchase a reamer from Scientific Cutting Tools. via MSC. ($145.00 roughly) A porting reamer makes a repeatably perfect surface for a union to seal on. It also spot faces the mating area and preps the hole for the 3/4-16 UN tap which follows the reaming operation.
The Chevy pump driven gear is locked in place by being press fit onto a knurled shaft. Feeling the need for extra safety I made a broach collar fot the odd size ID of the gear and broached all of my driven gears. The driving shaft will use woodruff keys.
Finished pump sections with SAE O-ring boss, O-ring grooved dividers and broached driven gears.
Stock Chevy pump bought for $13.99 at parts store. (Ruler shown for scale)
Trial pump section made to test backlash and gear to case clearances.
Here's the start. The pump sections being bored from one solid piece.
Gear end play was brought to "0" by sanding after facing to within .0005".
Pump spacer sections and bottom block start out as one piece. This helps alignment.
A pump spacer section being faced on the new lathe.
After the sections are assembled and bolted together they are turned on the lathe and moved to the mill for maching the flats. Here's another instance where my modifications to the rotary table helped me use every inch of the mill's table. My homemade lathe chuck adapter, pump and tailstock spanned the entire length of the Mill/Drill table.
A 1/8 slotting saw cut the groove for the broach collar. The broach is shown inserted in the groove. Before I learned anything about machining I always wondered how people put the female rectangular slot in the ID of pulleys and gears. Now I know!
SCT's reamer did a great job for the O-ring ports.
