FLO Headworks: 
Performance Specialists for
your Harley-Davidson® Motorcycles





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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 exhaust. 

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 particular cam.

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 e-mail us.

Related Articles

HD Porting Secrets

Dual Plugging

Tooled Finish

Super Port Flow

An Evo Big Twin Head with Super Port Flow

Test Data

Evo Big Twin Data Sheet

Evo Big Twin Flow Chart

For prices see below.



2000-2014, FLO Headworks. Contact Perry Kime at 805-481-6300 or via e-mail.
FLO Headworks, 1150 Pike Lane, #2, Oceano, CA, 93445.
All rights reserved. All prices subject to change without notice.
FLOHEADWORKS.COM and Perry Kime have no affiliation with Harley-Davidson® Motor Company. Trademarks and model names are the property of the trademark holders.