Reciprocating weight accelerates to a stop then changes direction. Rotating weight moves in a single direction. Loosely speaking, removing one ounce of reciprocating weight is more beneficial to longevity and efficiency than removing a pound of rotating weight. In other words, don’t waste time grinding the crank counterweights. Concentrate first on the rods, pistons, and pins.
• Using lightweight rods with stock pistons and pins can lead to disaster. The hefty stock parts can impart excessive tensile loading and fail the rods. Instead, get the lightest pistons and pins that still offer a surplus of durability, then spring for the light rods. Running light pistons on stock rods is safe.
• A too-heavy rod-and-piston assembly running on a lightened and scalloped crankshaft is an invitation to disaster. The crank can flex and fail at high rpm.
• If you’re stuck building an engine with marginal connecting rods, don’t install parts that increase engine speed (hot cam, ported heads, big carb, and so on). Instead, go with nitrous oxide, a blower, or turbo. Adding power through compressive loading is actually easier on the rods than the high-tensile loading that comes with screaming rpm.
• The root cause of as many as 80 percent of catastrophic rod failures actually begins when the big end loses its ability to maintain safe bearing clearance. The oil film gets displaced, the bearing grabs the crank, and the resulting kink-load snaps the beam.
• Contrary to popular myth, titanium rods will not evaporate if they come into contact with aerosol carburetor cleaner. What is true is that prolonged exposure to the stuff will cause oxidation that can cause surface inclusions and eventual