(US Patent #5,007,387)

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   ARAO Engineering's

 Twisted Version of Harley Davidson Cylinder Heads

4 VALVE HARLEY HEADS

 This head was designed for one purpose, HORSEPOWER.

     The advantage of 4 valves per cylinder is this. A HUGE valve area increase. As a comparison, most high performance cylinder heads for a  4" bore use a 2.0" intake valve and a 1.7" exhaust valve. The curtain flow area with 2 intake valves of 1.72" diameter each is equal to a single valve of 3.44" diameter. (curtain flow area is defined as the perimeter of the valve multiplied by the height of the lift, multiplied by 2 valves). And the curtain flow area of 2 exhaust valves of 1.476" diameter is equal to a single 2.953" diameter valve.

     With the 4 valve heads we generally use this huge valve area with the same size ports as used on a 2 valve head. In everyday terms we are OPENING the door faster, and keeping it open longer. This fills the cylinder more fully on the intake cycle and evacuates the cylinder more completely on the exhaust cycle. This reaches the same high port velocity as a 2 valve head, but maintains that same port velocity much longer. This is why there is no loss of low end torque, but much more mid range and top end power. 

     We designed the heads for use with all standard equipment such as manifolds, cams etc. for ease of installation for our customers and the cost savings of not needing top buy costly parts unnecessarily.

     Head kits come with everything needed to install. Pair heads complete, rocker boxes, rocker arms, and valve covers. 

     The heads are available now for:

• EVO with 4.0" bore and larger

• Twin Cam 95"cu. in. and larger    3 7/8" bore to 4.250" bore

• Twin Cam 4 3/8" bore and larger (relocated bolt holes)

*Patent Pending 

Intake port shows one port dividing into 2 valves.
Port flow @ 28” test pressure:
    LIFT      FLOW
.    100”     122 cfm
.    200”     226 cfm
.    300”     286 cfm
.    400”     308 cfm
.    500”     312 cfm
.    600”     317 cfm

Exhaust port view showing 2 valves merging into 1 port for use with standard aftermarket pipes. Exhaust Port flow @ 28” test pressure:
    LIFT      FLOW
    .100”     111 cfm
    .200”     184 cfm
    .300”     225 cfm
    .400”     241 cfm
    .500”     247 cfm
    .600”     248 cfm

 Showing combustion chamber face and 4 valves. Intake valve sizes 2: 1.732" valves (curtain flow area, which is height of lift  X perimeter of valve X 2 valves is equal to a single valve of 3.464" diameter. Note that most performance Harley heads come with a single 2" intake valve) This is the reason for the tremendous performance increase with the 4 valve heads. Bolt patterns come in EVO 4" bore, Twin Cam 3 7/8" bore and Twin Cam 4 3/8" bore and larger. Note all standard pushrods and pushrod tubes can be used.  Note standard intake and exhaust manifold angles and bolt up. Centrally located spark plug for the shortest flame front and modern fast burn chambers.

View showing front head, right side. 8valve logo and ARAO manufacturer name. Uses all standard pushrods and pushrod tubes. Shows cover, rocker box and head.

Left side of motor showing standard pushrod tubes. Standard intake and exhaust manifolds bolt on. And standard flat top pistons are used for 10.0:1 on a 113" motor.

Shows heads installed and right side of motor. Height of motor is exactly the same as a stock 2 valve head. Meaning no more frame clearance needed than stock heads.

Harley 8Valve Order Form

Boat and Marine applications

Have THE FASTEST Boat on the Lake!

  If you run a Chevrolet or Ford Engine in your boat, you could always use more raw HP, and extended RPM of 32  Valve Heads!

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