Starworks Motorsport has withdrawn its entry for this weekend’s Oak Tree Grand Prix at VIR, in order to concentrate efforts on the American Le Mans Series-ending Petit Le Mans later this month.

The Peter Baron-led squad made its Prototype Challenge debut last month at Circuit of The Americas with drivers Ryan Dalziel and John Pew, but the spec prototype, purchased from RSR Racing, suffered engine issues.

“With the motor-related problems at COTA, and last week’s [GRAND-AM] race at Lime Rock, we thought it’s better to skip the VIR race and really get the PC down to the last detail,” Baron told Sportscar365. “There are a ton of issues with the car that need resolving.”

It’s unclear what Starworks’ lineup for Petit will be. Dalziel is not expected to drive in the 1,000-mile/10-hour Road Atlanta enduro due to his driving commitments with SRT Motorsports, while Pew confirmed the COTA race was a one-off.

Starworks’ withdrawal from this weekend’s race at VIR leaves a 32-car field, including six PC cars.