For some time, I've been tinkering with stovebolt oil pumps, trying to figure out how to solve the problem of low oil pressure that seems to be a chronic problem with 216 engines, particularly ones with a few miles on them. The 216 presents a unique set of circumstances, since the connecting rods aren't oiled by passages drilled in the crankshaft. Streams of oil are squirted across the block just below the crankshaft, and dippers on the rods intersect the stream at the bottom of the piston travel when there's a minimum amount of load on the Babbit bearings. At idle, the rods are lubed by dipping into troughs that are filled by the squirt tubes. The clearance of the rods has nothing to do with maintaining oil pressure. The oil pump is tasked with lubricating the main bearings, the camshaft, timing gears, and the upper end of the engine- - - -rocker arms, etc. An "oil distributor" prevents any oil from going to the top end unless there's at least 15 pounds of pressure to the crankshaft. That's probably why worn rocker arms and shafts are found pretty frequently, and why the top end of some 216's looks pretty dry - - - -not enough pressure to open the oil distributor valve.
A 216 oil pump is a tiny thing, with very short gears. The full-pressure 235's use a similar pump, but the gears are about 1/4" taller than the 216 has. The most popular 235 replacement pump is the Melling M-45. I've found that with a little creative machining, the M-45 gears can be fitted to a 216 pump housing. The gears are the same diameter, but a spacer about 1/4" tall needs to be fabricated to take up the extra distance between the pump housing and the base plate when using the taller gears. Slightly different plumbing might also need to be done due to the height difference. There are other modifications, but nothing that a well-qualified machinist can't handle. The modified pump should flow about 20% more oil, with a corresponding rise in pressure.
Moving on to the 235- - - -a Melling M-55 pump for a small block V8 has gears about 1/4" taller than a 235- - - -once again- - - -the gears are the same diameter and pitch, and fit the 235 housing. A spacer and a new driven gear pivot shaft needs to be fabricated, the same as with the modified 216 pump. The output volume increase should be similar with the bigger gears in the 235 pump.
Then there's the final step- - - -I'm just about to see if there's a way to build a fixture that will allow a complete small block V8 pump to be bolted onto either a 216 or a 235, and be driven by the bottom of the distributor shaft. That would require a little creative plumbing and some test-fitting to be sure there's adequate room between the side of the oil pan and the crankshaft, but I think I've got the drive system just about planned out on paper before I start whittling on steel! More to come!
Jerry
