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Screw-type Superchargers Headed to NHRA Pro Mod in 2022

A rule supplement posted to today confirmed rumors swirling since mid-season that the NHRA’s quarter-mile Pro Modified eliminator would indeed see the inclusion of yet another engine and power adder combination in 2022.

The rule ammendment now identifies six different combinations legal for the popular doorslammer series with the addition of Screw Supercharged entries limited to 526ci and weighing in at 2,740-pounds, along with two variations of Nitrous-assisted entries, Roots Supercharged, Centrifugal Supercharged and Twin Turbocharged entries.

Specifically, it will be NHRA accepted, Screw-type, C rotor, superchargers permitted for use in the E3 Spark Plugs NHRA Pro Mod Drag Racing Series presented by J&A Service that must meet SFI Spec 34.1 and be reinspected by the manufacturer every three years. Manifold burst panel meeting SFI Spec 23.1 (in addition to panel in supercharger) plus restraint system meeting SFI Spec 14.21 will also be mandatory. Maximum overdrive limit for the screw supercharger is 75-percent and variable multi-speed supercharger devices are prohibited.

The rule amendment also allows for the inclusion of 1949-1950 Mercury bodies to take advantage of a 50-pound weight break for select nostalgia body styles.

The Screw Supercharged combination will be two-hundred pounds heavier than the eliminator’s lightest combination (910ci max) Nitrous-assisted entries and the heaviest overall. For comparison, 960ci Nitrous-assisted entries (960 cid) must weigh at least 2,570 pounds, Roots supercharged entries (526ci) a minimum of 2,640 pounds, Centrifugal supercharged entries (526ci) 2,735 pounds and Twin Turbocharged entries (526ci) come in at a minimum of 2,615 pounds.

This story was originally published on November 5, 2021. Drag Illustrated

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