The Auto Club Dragway’s recent construction of a county-mandated sound wall has allowed the facility, located adjacent to the two-mile NASCAR oval in Fontana, California, to re-open its gates for drag racing competition after a nearly two-year hiatus. But just as the track had dealt with before being shuttered, specific decibel level limits have been mandated and are being strictly enforced, and as we learned last week, early testing to determine the feasibility of bringing the loudest of the loud race cars on their schedule to the facility — roots and screw-blown Pro Modifieds with zoomie-style headers — failed to meet the criteria for sound limitations.

As a result of this testing, the NMCA WEST technical staff has ruled that roots blown combinations, with their current exhaust configurations, will not be allowed to compete in NMCA WEST Pro Mod competition at the three events that are slated to be run at Auto Club Dragway. 

“The Pro Mod Class will still be contested at the three Fontana events with Turbo, Naturally Aspirated, Nitrous, and Centrifugal Supercharger combinations,” said Rollie Miller, National Event Director at NMCA WEST. 

Pro Mod veteran John Scialpi, along with John Durden, are among the few regulars in the category to run a blown combination. Wade Maggio, Lee Smith, and others run with the series on a limited basis.

Miller added, “If Blown Roots Blower combinations can modify their exhaust and come in under the 85db limit, they may compete at Fontana in NMCA WEST Pro Mod.  John Scialpi is currently working on several header and exhaust baffle/muffler combinations with Flowmaster and will attempt a sound test in coming weeks to see if any of his combinations will adhere to the decibel limit.”

The decibel requirement on California roadways is 92 db, which might lead some to wonder why a 3,000 horsepower race car would need to run quieter than a street car. However, as has been suggested but not confirmed, the decibel levels are being recorded on the opposite side of the sound wall, or perhaps even close the nearest neighboring homes. We’ve reached out to the folks at Flowmaster to find out more about their efforts to help get the supercharged racers under the decibel ceiling, and will issue a follow-up to this story shortly.