Competition Connecting Rods – Only the Strong Survive.

Competition Connecting Rods – Only the Strong Survive.

By Sam Logan: Nothing undermines the legitimacy of a connecting rod maker more than a deficient batch of rods. He agonizes constantly about heat treatments, high revs, heavy pistons, heavy pins, the number of race laps between rebuilds, but probably most of all whether or not nitrous is being sprayed. It’s a complicated business determining minimum weight while yielding maximum strength, enough to withstand the abuse sustained by the average race motor. Dyer’s Top Rods overcomes these special problems with their connecting rods by forging them in 4340, a very tough material with high nickel and high molybdenum content. In fact, the chemical constituents of the rods are almost identical to the dies from which they are forged. Probably the chief reason they consistently withstand high impact loads at high temperatures is because they are subjected to a special heat treatment, a painstaking process closely governed in a batch furnace. To this end, controlled quenching and elaborate racking procedures maintain the stability of the connecting rods during the procedure.  Though Magnaflux testing (which uses dust in a magnetic field to reveal cracks on the rod’s surface) has been in use for decades, “It was sonic testing that had the most profound effect on the quality of Dyer’s Top Rods,” says company president, Roger Friedman. In use for most of this decade, sonic testing is characterized by a sound wave transmitted through the metal, revealing any hidden internal inclusions. Under high stress conditions, inclusions or ‘cold shuts’ can be fatal to the connecting rod’s longevity. For performance as well as practical and economic reasons, most competition small-block V8 engine builders...
Rod stretch and rod bolt fatigue: Beerhorst talks boosted engines

Rod stretch and rod bolt fatigue: Beerhorst talks boosted engines

Written by Moore Good Ink: When the crankshaft pulls the connecting rod downward on the induction stroke of a naturally aspirated engine, a stretching load is exerted on the con rod because the piston area is so much greater than the column of air being drawn into the cylinder. In contrast, when the inlet valve is open on a boosted engine, the rod is always under pressure, not a stretching load. Therefore the life of all rotating parts in the boosted engine is significantly prolonged. Of course, there is also a stretch on the rods when the throttles are closed and the engine is decelerating. It’s under these conditions where most con rods fail on oval track cars: when the throttles are closed as the car approaches the corner. Consider that situation for a moment: the piston is sealed to the bore by the rings and the crankshaft is pulling it down against huge resistance. Remember, the throttle plates are closed so there’s not much air pressure in the combustion chamber to assist.  A streetable naturally aspirated engine producing 2,000hp doesn’t exist. But if it did you’d be lucky if the engine’s rotating parts survived for more than a few quarter-mile passes. There are, however, large displacement maximum-effort engines operating near this power range, but they are not streetable and only the most durable could complete 50 quarter-mile passes without a rebuild. In contrast, when you boost the engine, it will make this vast amount of power and you could run it on the street. Using lower engine speeds and with less radical valve train it will run for...