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Valve springs are Chevrolet’s engine culprit

April 7, 2015

Further information concerning the non-minor repairs of Chevrolet Verizon IndyCar Series engines has come from Jim Campbell, Chevrolet’s U.S. vice president for performance vehicles and motorsports that puts a face on the problem.

“We identified a batch of valve springs that, due to a process change at one of our suppliers, may fracture before the full mileage requirement (2,500 miles). We notified INDYCAR of the issue and obtained approval to change the valve springs.”

The change was made to 11 of Chevrolet’s 12 INDYCAR engines as the final engine had “lower accrued mileage. The current plan is to address the 12th engine after the race at Barber Motorsports Park,” the fourth race of the season on April 26 and the third consecutive event this month.

INDYCAR had already confirmed, “The non-minor (major) repair that Chevrolet performed on 11 of its engines was completely legal and above-board with respect to the rules,” according to Marvin Riley, INDYCAR director of engine development. “We were notified of the change and an INDYCAR representative was present for the entire repair process, even resealing the engines before departing their facilities (Ilmor Inc. in Plymouth, Mich.). The points penalty [results] because the engines did not go the full 2,500 miles without a major repair.

“Chevrolet replaced like-for-life parts in their engine when making their repairs, so no new or unapproved parts were installed. The repair involved only replacing used with fresh parts,” Riley said.

Valve springs can be manufactured using heat processes and could be susceptible to breakage in extreme conditions experienced in the Verizon IndyCar Series. Tool steel materials used in the triple-spring used in this type of racing can vary from batch to batch and it would seem that is the issue here. A brittleness can occur when the material is not sufficiently durable for this type of endurance work.

This is a pair of NHRA Pro Stock valve springs - simply offered for identification purposes - Anne Proffit photo

This is a pair of NHRA Pro Stock valve springs – simply offered for identification purposes – Anne Proffit photo

While this isn’t a common problem for Indy cars, getting valve springs to live for long distances in drag racing, particularly in Pro Stock competition is often quite difficult. The amount of lift and cam work done on an engine is critical to valve spring life, in particular for the elongated distance of 2,500 miles as decreed by INDYCAR. In NASCAR, for instance, valve springs are typically changed out for every race but with seals on the engines, that’s not possible to do on an Indy car.

By finding this defect prior to it hurting the rest of the engine, Chevrolet might have paid a smaller price than it would have with catastrophic engine failure due to valve spring issues.

By Anne Proffit

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