1972 350 Chevrolet Pickup Engine - Tech - Build Your First Engine

The crank gets a thorough cleaning prior to assembly using an oil galley brush. Several bits of metal and some loose grinding-stone debris were extracted. Note the fully radiused fillets and chamfered rod and main oil transfer holes-standard features on the Powerhouse cast-iron stroker unit.

A classic assembly boo-boo is installing the rear main seal backwards and causing a massive oil leak. Here the pen points out the raised lip of the seal, which always faces inboard toward the oil. A thin coat of Gasgacinch sealant was applied beneath the rubber seal inserts in the block and in the ream main cap. A small dab of self-drying Permatex Number 1 at the edges of the seal offers further leak prevention. Applying too much will foul the rubber seal and forge an oil-leak path.

With a coating of Torco assembly lube on the main bearings, the crank dropped in place. Note that the upper main bearing shells are grooved and are made with oil-feed holes to match those in the block's main bearing saddles. Don't make the mistake of installing the nongrooved and undrilled solid lower main bearing cap inserts in the block. It'll eliminate oil flow to the crank and wreck the engine within seconds.

The Powerhouse-supplied Hastings moly-faced piston rings (PN 2M 139 030) come pregapped at 0.016 inch. Just to confirm, we used an inverted piston as a squaring tool and installed each ring into the block so we could check the installed endgap with a feeler gauge, and it was spot-on. For naturally aspirated street/strip engines like this, you want 0.004 inch of ring endgap for every inch of cylinder bore (0.004 x 4.030 = 0.016). Nitrous and forced-induction applications require more endgap, as much as 0.006 inch per inch of cylinder bore, to ensure survival.

Unless you're a seasoned veteran, never install piston rings by hand. They're all too easy to bend, and the moly coating can fracture if you're not careful. Instead, use a proper ring expander.

Cleanliness is key throughout the entire assembly. After each bore was cleaned thoroughly with aerosol brake cleaner (dries without leaving sediment), a light film of 30-weight oil was hand-rubbed onto the bore and piston rings. Then a tapered-collar piston-ring compressor was used (you could use a clamp type) to load each piston and rod assembly into its bore with plastic covers on the rod bolts to protect the crank from nicks. Note that the piston is marked "front" to correctly orient its pin offset. You did remember to index each of the Powerhouse kit's clearanced rod bolts inboard during piston-pin installation so they wouldn't hit the camshaft, didn't you?

Here's the finished short-block. It's an extremely rugged foundation for serious horsepower, and the quality machine work will ensure the fun lasts a long time. Next, we'll build a house of horsepower on this solid foundation and show you all the tricks.