Three years ago, in an effort to control escalating long-term costs in the alcohol categories, NHRA released a moratorium on cylinder blocks and head designs that allows only engine combinations used prior to April 1, 2001. After careful review, the NHRA technical department is clarifying the modifications that will be accepted and the dimensions and specifications that must remain unchanged (see below).

AMENDMENT TO 2004 NHRA RULEBOOK - April 26, 2004
SECTION 8 - TOP ALCOHOL DRAGSTER - ENGINE

Only those engine combinations that utilize cylinder blocks and head designs that were in NHRA competition prior to April 1, 2001, will be accepted for NHRA competition. Any modifications or alterations to cylinder blocks and head designs used prior to April 1, 2001, other than those listed below, will be deemed to be a change in design and therefore prohibited. Engine combinations that do not meet the following criteria but were used in NHRA competition in 2003 will be accepted through the 2004 season only. For a complete list of cylinder blocks and head designs that are allowed in NHRA competition, contact the NHRA technical department: phone, (626) 250-2485; fax, (626) 914-7551.

All engine combinations must adhere to the following criteria:

1. Maintain interchangeability of existing parts (i.e., cranks, cams, manifolds, valve covers, rocker assemblies, etc.)
2. Maintain original bore center variance of +/- .015-inch
3. Maintain maximum camshaft-to-crankshaft centerline variance of +/- .015-inch as used prior to April 1, 2001
4. Valves can be any size as long as they maintain intake and exhaust valve-angle variance of +/- 1 degree
5. Maintain general combustion-chamber configuration (e.g., Hemi, canted valve). Fuel injection directly into cylinder prohibited
6. Maintain original cylinder orientation in reference to centerline of crankshaft
7. Maintain valve-guide location, lateral and front to back, variance of +/- .015-inch
8. Maintain lifter-bore location, lateral and front to back, variance of +/- .015-inch
9. Maintain maximum and minimum (+/- .015-inch) engine-block deck-to-crankshaft centerline dimension as used prior to April 1, 2001
10. Retain cylinder head, timing cover, intake manifold, exhaust manifold, valve-cover bolt pattern; additional bolts/studs/dowels may be used
11. Retain as cast/forged minimum block wall and web/rib thickness

Note: Effective Jan. 1, 2005, the maximum allowable bore center spacing will be 4.840 inches on all engines used in Top Alcohol Dragster and Top Alcohol Funny Car competition.