Contrary to popular myth, serious power can be made with
stock Harley-Davidson heads without reshaping the combustion chambers, polishing the ports
and combustion chamber, using a larger intake valves or making the ports larger. A good
'street or pocket' port consists of improving the air flow around the valve seat and valve guide
areas of the head. A good 5 angle valve job is performed, and the heads are ready to go on
the bike. Heads reworked in this manner should see increased air flow over stock heads of
10-15%. That should be more than enough to create a 90 HP engine with the proper pistons,
carburetor, camshaft, exhaust system and ignition system.
What goes into a good set of performance heads? All you
need is the proper port shape, the proper valve sizes to allow good air flow, the right
springs to keep the valves properly seated and the right compression ratio for the power
Proper installation of the cylinder heads is critical to
engine life and performance. Did you know there are two different ways to install the
cylinder heads on a Harley-Davidson engine? Instruction are provided for both ways.
To learn more about cylinder heads, port design, valve
sizes, compression rations, installing a new set of heads and more, just click on
the item in the menu you want to know about.
Cylinder Head Installation
Cylinder Head Bolt Torque Values
Cylinder Head Port Design
Cylinder Head Valve Sizes
Cylinder Head and Piston assembly
Bolt Torque Values