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Super Team

AJR-Racing Blaine-Johnson

481-X Stage IV Cylinder Heads

The Stage IV 481-X is now available…The newest improvement to the AJPE 481-X engine platform. Fitted with the latest requests from engine builders and racers, AJPE has re-designed the top side of the cylinder head and rocker stand to withstand higher engine speeds and boost levels.

 

  AJPE Stage IV 481-X Cylinder Head

 

The Stage IV 481-X cylinder head is the lightest, most advanced 481-X cylinder head AJPE has made to date. An entire re-design of top, bottom, and ends of the cylinder head allows for five additional rocker stand fasteners for maximum rocker assembly stiffness and a reduction of over 5 pounds per cylinder head. This is the most rugged and advanced 481-X cylinder head available…period.

  

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 36.6 lbs. each
  • Over 5 lbs. per head lighter than Stage 1, 2 or 3)
  • 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, and Intake manifolds. (Stage I & II intake manifolds require modification to fit on Stage 4 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.

 

***Requires AJPE Stage IV Rocker Stand and Valve Cover***

 

 

.900

 .800

 .700

 .600

 .500

 .400

 .300

 .200

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

497

 

477

 

458

 

427

 

374

 

308

 

229

 

147

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

347

 

334

 

315

 

292

 

259

 

219

 

178

 

131

 

 

 

 

 

 

 

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

 

01B-004-08-JH   481-X Stage IV Billet Cylinder Heads, 50° Valve seats. Program #09. Bare, CNC ported ready to assemble, with Jr Hoops @ .018 out. (without Girdle Plates) (pair)