NHRA J&A Service Pro Mod Competitors,
We are making an update to the rule concerning the previously announced bore spacing rule for 2018. Turbocharged billet hemi cylinder head entries will now be limited to 4.800 instead of 4.900. Please see the changes to the rule book wording below. As we have mentioned before and I will reiterate here; if engines with the larger bore centers begin exhibiting a performance advantage they could be treated as a separate combination when parity adjustments are made.
We are also making an update to the rules pertaining to lock-up converters. Lock-up converters will be permitted on nitrous-assisted entries only. With this new rule, nitrous-assisted entries with a lock-up converter will be treated as a separate combination with respect to parity adjustments and will receive a 25 pound minimum weight increase to start the 2018 season. This will mean that at the start of the 2018 season nitrous assisted entries without a lock-up converter will have a minimum weight of 2,425 pounds while those with a lock-up converter will have a minimum weight of 2,450 pounds. The NHRA Technical Department will be watching this new nitrous-assisted lock-up converter combination closely and will not hesitate to make a parity adjustment quickly if needed.
SECTION 5: NHRA J&A SERVICE PRO MOD DRAG RACING SERIES, ENGINE:1, ENGINE (Page 2) (For 2018 season)
Internal-combustion, reciprocating, single-camshaft, 90-degree V-8 automotive-type engine mandatory. Crankshaft centerline must intersect cylinder bore centerlines and be symmetrical. Nitrous-assisted entries are limited to a maximum bore center of 5.300. Turbocharged entries are limited to a maximum bore center of 5.000. Maximum bore center on turbocharged billet hemi cylinder-head entries is 4.800 inches, 5.000 inches on all other turbocharged entries. Maximum bore center on supercharged billet hemi cylinder-head entries is 4.900 inches, 5.000 inches on all other supercharged entries. For supercharged entries, a positive method (flange, lip, etc.) must be attached to the intake manifold or engine block to retain both the front and rear manifold to block gaskets in the event the engine crankcase/lifter valley becomes over-pressurized. The flange/lip must extend past the surface of the gasket and be contoured to closely fit the block and manifold surfaces to prevent the gasket(s) from extruding. See General Regulations 1:2.
Vice President Technical Operations