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481-X Stage III Cylinder Heads

The Stage 3 481X cylinder head…bigger valves, bigger ports, improved rocker assembly, equals more power from this AJPE combination.

  AJPE Stage III 481-X Cylinder Head


The AJPE Stage III 481-X cylinder head is the cylinder head of choice of Eric Dillard and Steve Petty of Proline Racing Engines and their Championship Turbocharged 481X engine program. Larger port area with improved valve and rocker placement allows for large od pushrods for improved valve action and stability. This cylinder head accepts all current 481-X blocks, valve covers, headers, and intake manifolds (Stage I & II Intake manifolds require modification to accept the Stg III head)


Standard Features Include:

  • 73cc Chamber volume
  • 2.450” Intake Valve (11/32 stem diameter)
  • 1.920” Exhaust Valve (11/32 stem diameter)
  • 50° Intake and Exhaust Seat Angles for improved seat life over 55° seats.
  • Accepts .500 diameter intake pushrod and .565 diameter exhaust pushrod
  • Copper alloy Intake and Exhaust seat material.
  • Steel Valve Guides with Bronze liners.
  • O-Ringed Intake ports for optimum seal and ease of assembly.
  • Decks machined for AJPE designed Jr Hoops. @ +.018 protrusion above deck.
  • Bare cylinder head weight 41.3 lbs. (over 1.5 lbs. per head lighter than Stage 1 or 2)
  • Accepts 1.670 triple springs. (2.200 installed height with +.100 retainer)
  • ½” head studs with steel hat washers installed.
  • Accepts AJPE Stage I and II Header flanges, Valve covers, & Intake manifolds. (Stage I & II intake manifolds require modification to fit on Stage III head)
  • All head studs are accessible from the top of the cylinder head. No inner head studs to deal with.
  • Manifold can remain in place when removing cylinder heads from engine for ease of service.
  • Machined to accept 14mm x .750 reach, “Gasket style” 13/16 hex spark plugs.
  • 4.500 minimum bore diameter
  • High Strength, Made in the USA 6061-T651 Aluminum Billet material.
  • 100% CNC Ported for AJPE Accuracy, Performance & Consistency.
  • Supplied completely finished ready to assemble out of the box.











2.450 Intake Valve
551cc   4.500 Bore
(#08 program)
















1.900 Exhaust Valve
198cc   4.500 Bore(#08 program)
























All flow tests performed on Super Flow 1020 @ 28”, Exhaust tested w/ 2.500” od. pipe.


01B-003-08-JH   481-X Stage III Billet Cylinder Heads, 50° Valve seats. Program #08. Bare, CNC ported ready to assemble, with Jr Hoops @ .018 out. (without Girdle Plates) (pair)