Here is part of a previous discussion:
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=008745#00 0010 The oil system in the old 216s is known as a low pressure system because the main pressure when warm and at medium RPMs is around 15 lbs. At idle it is 7 lbs or less.
Babbitt: The rod bearing surfaces are made of babbitt which is formed directly on the iron of the rod bore. These rods are shimmed for clearance adjustment. The more modern rods have insert bearings and they usually have several different layer of different metals, the mating surface being babbitt. Babbitt is a soft material with a high lead content. It has the ability to conform to the crankshaft surface.
The rods in the 216 are not fed with pressure from the crankshaft/main bearings. The early 216s had only dippers on the rods, like most early motors. As everyone else moved to pressure oiling of the rods, Chevy beefed up the old design by providing "rod sprayers" that spray directly into the dippers as the RPM builds past idle.
The 216 main oil system branches out from the pump, to the main bearings and camshaft, and to the "oil distributor valve". This little valve, located under a cover on the driver's side of the block, opens up after the RPM and pressure builds up, to supply oil to the rod sprayers and also the rocker arm. To supply the rocker arm assembly, there is a line that emerges from the block, just back of the oil distributor valve. This line loops back into the block, passes through the water jacket and goes up to the rocker arm , passing through the area of the lifters, under the side cover. Chevy claimed that this was to heat that oil to the right temperature. I think that it was just their way of routing the line.
I sent a PDF file to some of our members here detailing the oil line. Also there is an installation instruction in the Chevy truck manual.
