Even as the aftermarket industry develops crankshafts that are harder to break, racers get better and better at breaking them. “When we’re at the PRI Show,” said Dave Olsen of Mile High Crankshaft, Denver, Colorado, “about a third of the questions we get are about repairing cracked crankshafts: ‘Can you fix it, and how much will it cost?’”
The answer to “can you fix it” can be complicated, but a lot depends on the depth of the crack versus the journal diameter, “and how bold the crack looks in Magnaflux. If it’s extremely bright, that tells us it’s well-defined. We also look at the crack, and draw an imaginary line from point to point, to get a decent idea of how deep it is in the radius. And if we have to grind out or vee-out more than a quarter inch in depth, then we don’t feel good about attempting a repair,” explained Olsen.
The length of the crack is much less of a concern. “We get cranks with a crack that’s an inch long, and we’ve been very successful at repairing those. We’ve repaired cranks that have raced for another 10 years,” he added.
Mile High does custom work as well as repairs. And some racers combine the two. “Let’s say for an example a small block Chevy that has small-journal connecting rods. If the crank is damaged, they may have hurt one or two rods also, so they elect to convert to Honda-size journals. That’s become real common, where we grind a damaged journal down to a smaller diameter. And the racer might pick up some performance just due to the lighter weight.”
Nick Boes of Shaftech in Fostoria, Ohio, emphasized how repairing a crank can take less time than replacing it. “The lead times for most new crankshafts are approaching 12 weeks in most cases, which is the better part of most racing seasons. Whereas we can take an existing shaft and repair it, or modify it to suit another need, in two or three weeks. That can have a real impact on a racer’s or engine builder’s year.
“Consider, also, the variations in stroke and journal bearing sizes that can run in the same class, where competition is so tight that everyone is looking for an edge,” added Boes. Shaftech does “quite a bit of journal repair, and re-grinding and nitriding of both repaired and previously un-nitrided (i.e. OEM) cranks. Our custom work ranges from off-setting strokes on everything from motorcycle to diesel tractor cranks, to adding counterweights, to Omicron surface finishing.”