After years of research and development we
are pleased to offer a major breakthrough in the volumetric efficiency
for the Evo Big Twin engine.
Our patented Tooled Finish in the ports
has effectively doubled the atomization factor over the polished surface
used by other head porting companies. The result is greater power and
smoother running than the competition can offer.
Another interesting discovery that
applies to the H-D V-twin engine is the exhaust to intake ratio of the
air flowing through the ports. Generally speaking they like a fairly
high ratio around 90 to 92 percent at . 500"lift. The stock
Evolution castings stock tested at 78 percent at . 500" lift.
The process of events that lead to a
significant increase in the flow characteristics throughout the entire
range of valve lift is lengthy and tricky to say the least. Our flow
bench techniques have enabled us to improve the low lift flow of both
the intake and exhaust ports arriving at exhaust to intake ratio of 88
percent at . 500"lift.
This will give the engine a smoothly
tuned effect even with some of the more radical cams. The high lift flow
at . 500"lift has been increased in the intake port by 11 percent
and in the exhaust port by 25 percent. During this process a large
amount of metal is removed from the ports and combustion chamber area.
The seat pockets are polished with a radius up to the valve seating
area. The combustion chambers are matched to your bore size and polished
to give the most effective flame travel.
Dual spark plug conversion is the finishing
touch to give your engine its full potential. The valves are hand made
in-house from 21-4N stainless steel with polished tuliped heads.
The backside is machined with a
.750" radius to increase the flow characteristics and nitrided
along with the stem to minimize wear.
The valve seating area measures .
060" wide on the exhaust valves and .045" on the intake
valves. The head diameter has been increased by 20 percent to
1.687" on the exhaust and 1.937" on the intake. Valve stem
clearance is fit to .001" on the intake and .002" on the
This high performance cylinder head
modification package includes:
• Matching and reshaping the intake
manifold with our Tooled Finish to atomize the incoming fuel
• Hand lapping the head gasket surface
on the Microflat.
• Glass beading or painting.
• Testing valve springs.
• Assembly with our all Teflon valve
stem seals to the specification required by manufacturer of your
Our work and products are guaranteed for
one year. For an estimate on your particular application contact us
directly by telephone at 805-481-6300. Or you can