Revolution Performance Motors has introduced the RPMHemi 4 valve heads for the Evo V-twin and early Twin Cam engines, Twin Cam EFI kits are currently being tested and will be available soon. If someone asks, "That thing got a hemi?" just install these heads and you can say yes. Sweet! The heads bolt directly on to the stock engine, the only changes required are valve clearance pockets must be cut into the pistons and the exhaust must be modified.
RPM has both conversion kits or complete engines in several displacements. There's also an intake plenum that mounts 2 carburetors, the second CV carb serves as a vacuum secondary for high RPM runs. The heads fit any bore size from 3.5 to 4.25 inches. The hemi combustion chamber and center location of the spark plug as well as less spark advance allow compression to increase from the stock 9:1 to over 11:1. Evo kits start at $2995, Twin Cam kits from $3099.
4 valve heads can dramatically increase engine breathing and with no other modifications, engine horsepower and torque increase by 15 to 20 percent, with gains everywhere in the RPM range but it's especially dramatic above 4000 RPM. Modified engines will see even bigger gains. Engine height is 1/4 inch lower with the 4 valve heads than with the stock configuration.
These 4 valve hemi heads seem like a pretty nice setup, either alone or as the first step before further modifications, and they would seem to be just right for a big twin powered sport bike or cafe racer. It will be really interesting to see some back to back performance comparisons.
Press release follows:
Ever hear of a V-twin Evo or Twin Cam motor with approximately 85% of available torque coming in at approximately 1500 RPM? We have! At RPMHemi.com we do it all day long with our patented 4 Valve Hemi Bolt on Head Conversion Kits. “This is simply the best performance bolt on for the buck in the V-Twin market!” states Phillip Holmes, VP of Marketing & Sales for RPMHemi.com. You can estimate an approximate 20% power gain. This is a proven technology with both street and racing applications.
How it works: Utilizing our patented 4Valve system in a hemispherical combustion chamber we can increase airflow 1.5 times, increasing the compression ratio while maintaining a 25° spark advance, which gives an equal full burn in the chamber, while preventing pre detonation. All this in a package that is ¼” lower than stock heads. Our headsets and engines are also low in emissions.
RPMHemi.com manufactures their patented 4 Valve Hemi Head Kits and sells complete 97”, 107” and 114” motors with or without our 4Valve Hemi Heads and we have our patented Ram Chamber for single and dual carburetor V-Twin applications.
Currently, we have several OEM motorcycle manufacturers testing our products and all looks good.
UPDATE: The link previously posted in this article has been inactive for some time. We have had many inquiries about these heads and the company that was producing them, however, efforts to contact the company or anyone previously associated with it have been unsuccessful. If anyone has further information of any efforts to continue production of this 4 valve head, please let us know through the contact form. Thanks. Paul Crowe
Revolution Performance Motors