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

Next came a thorough magnaflux inspection. Cracks are commonly caused by stress, freezing, and overheating. Most cracks caused by freezing will be manifest in the water jackets above the oil-pan rails, in the lifter valley, and by the freeze plugs. Cracks caused by overheating will be seen on the decks and in the lifter valley-in the case of a clogged exhaust heat-riser passage in the heads and intake manifold. Stress cracks are typically found around the head-bolt holes on the decks and by the oil passages on the main bearing saddles.

Our 350 checked out A-OK, but if you do find a crack, this is what it looks like. Note that the cracked lifter-valley surface has disrupted the magnetic field and caused the magnetic powder to form a line highlighting the flaw. Not all cracked parts are scrap-bin fodder, but you must weigh the cost/benefit ratio.

Typical crack repair involves welding or inserting a string of threaded taper plugs from one end to the other. This is called cold crack repair, and each plug fits into a hole that must be drilled and tapped in an overlapping fashion. Once the plugs are installed, they are ground flush with the surrounding metal. The big limitation to this type of crack repair is access-you have to be able to get into the area with a drill, tap, and grinder.

With the happy news that our 350 block was free of cracks and other fatal flaws, we chased all threaded holes to ensure clean threads and that none were crossed or stripped. Thread repair isn't especially expensive, but it can leave considerable grit that is best generated prior to cleaning. It is also best to find (and repair) trouble spots at this early stage instead of during final assembly.

Here's the scene after complete teardown. Much of what's shown will not be reused (reciprocating assembly, oil pan, oil pump, camshaft, timing set), but it's a good idea to keep everything around until final assembly is complete. Sometimes helpful clues can be learned from the wear patterns on the old parts to guide the remanufacturing process.

With every press-fit and screw-in plug removed, the bare block was loaded into the pressure washer where jets of scalding, 180-degree-F detergent removed all traces of grime and dirt. An alternate cleaning method is a steel-abrade cabinet, which makes parts look brand new. The only reservation is that the steel shot is more aggressive than the pressure washer and can degrade still-useable cylinder bore finishes. Because our block's 0.030 oversize bores were within spec, we needed to protect them, so steel-abrade cleaning was off-limits for us this time.

Though our 350's stock crankshaft and connecting rods passed inspection, refurbishing them for reuse is a false economy when for less money you can buy a prebalanced 383 kit from Powerhouse. The kit comes with a brand-new 11/44-inch cast-iron stroker crank (0.270 inch, to be precise) and everything else shown here for $879.

The Powerhouse 383 kit includes brand-new 5.7-inch 5140 alloy forged steel rods with polished and shot-peened beams and ARP 31/48-inch fasteners. JMS' Mike Johnson says he used to charge $250 to blueprint a set of stock rods prior to the advent of super-affordable aftermarket goodies like these. Again, it just isn't cost-effective to refurbish certain parts during a rebuild like this. New parts are better and less costly.

The ready-to-install Powerhouse rods come with a small area of clearance grinding on the head of one rod bolt. The other rod bolt is untouched. The massaged side of each rod is to be installed inboard to guarantee cam clearance.