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312 Y-Block Build-up  Part 2
by Larry D'Argis



For my '57 Fairlane 500 restoration I wanted an engine that had a bit more power than the old 292 provided, so we started with a 312 short block assembly from a '56 Monarch.  After the block was cleaned and magnafluxed to check for cracks it was bored .040" over to accept a new set of Sealed Power pistons fitted with moly rings.  The moly rings are now available for all 272-312 Y-Block V8s and unlike the older cast rings that require a break-in period, the moly rings seat almost immediately on start up.


We also had the machine shop drill two holes in the block between the center cylinders.  The holes lead directly into the water jacket and will correspond with two holes we had drilled in the cylinder heads.  This will allow additional water circulation between the two center cylinders, relieving a hot spot caused by the two adjoining exhaust valves.  Modern Y-Block head gaskets have these holes and there are usually detailed instructions included that show how to locate and drill both the block and heads.

The crankshaft was turned .010" on the main and .020" on the connecting rod bearing surfaces and we used a good set of Clevite 77 bearings.  We also had the engine machine shop install new Clevite cam bearings as well.  The connecting rods were fitted with new ARP high tensile strength rod bolts and then resized before the entire reciprocating assembly was balanced.  The balancing ensures that all of the piston assemblies (piston, pin, rod, rings bearings) are of equal weight.  If you've ever heard the phrase that, "it runs so smooth you could put a coffee cup on top of the air cleaner and not spill a drop", that's a well balanced engine.  In our case we used two connecting rods from a different engine and wanted to be sure everything balanced out, so there wasn't any chance of a rough running engine.


With all of the parts in hand, Albert turned the block pan side up and installed the sixteen mushroom lifters.  This is the only way to put lifters in a Y-Block before installing the camshaft.  Then came the crankshaft main bearings and the crankshaft itself was torqued to spec.  Next the pistons were installed on the connecting rods, then the rings and top connecting rod bearings.  Each piston was then gently tapped into the cylinder bore and the bearing caps torqued to spec.

To ensure good oiling we chose a blueprinted Melling oil pump from Precision Oil Pumps in California.  Their pumps use moly-coated gears and are built with very tight tolerances for smooth and constant oil delivery.  We followed it up with one of their 3/8" CNC machined, 4140 billet Chrome Moly pump drive shafts, to replace the wimpy factory ¼" drive.

Up next, we'll look at the camshaft that was selected and the timing set we used to line everything up and get the maximum power and torque for the 312.