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Engine Parts > Cylinder Heads

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For the past two years we have been developing an aluminum head for the 4.0L Jeep engine. This head will replace the stock cast iron head on all 4.0L engines made from 1991-2007. It will also fit the 1986 through 1990 engines by using the late model intake manifold.  It has all the necessary accessory bolt holes including the coil pack hold down bosses for the 2000-2007 engines. 

This aluminum Jeep head is an ideal upgrade for the 4.2L engines, but does require updating the intake & exhaust.  Replacing the stock 4.2L head with our high performance 4.0L head increases horsepower and torque throughout the rpm range.  It is especially viable for fuel injected 4.2L engines with detonation problems from low octane fuels. Combustion chamber temperatures are greatly reduced due to the improved heat dissipation with our aluminum Jeep head, addressing not only the poor quality of fuel, but also the NOX portion of emission testing implemented in some states. The water jackets (usually requiring filling or welding) have been eliminated.

One of the most important features of our new aluminum Jeep head is the 30 pound reduction in weight. It weighs in at about half the weight of a stock cast iron head. We were able to achieve this weight advantage even while adding extra material in several areas.  Our 5/8" thick deck reduces the possibility of warping, 
and we added extra material around the runners for porting up to 0.250", and extra material under the springs to accomodate machining for oversize springs. 

After extensive flow testing and dyno testing, we retained the stock valve sizes, and went with high performance springs, hardened seats & silicon bronze guides.  The rocker bosses will accept either the stock rocker arms and pivots or roller rockers, and the valve cover mating surface has been raised to accomodate the roller rockers without a valve cover spacer. 

The most unique feature of our new aluminum Jeep head is that the push rod holes have been enlarged to allow the lifters to be retrieved without removing the head. Camshaft changes will be a snap instead of a half-day ordeal. 

MADE IN THE USA by HESCO!!  THESE SERIALLY NUMBERED HEADS ARE CARB REGISTERED!!!   EO# D-592. 

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