and YES it is exchange, and still not cheap!
from http://www.petermaiden.co.uk/combinedframe.html
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As a partner to the automotive industry Shrick develops complete engines.
Camshafts are a key component in the kinematic system and vital to the
dynamic properties of an engine. Shrick specialises in camshaft design and
is a high precision manufacturer of thios important central component.
IMPROVED ENGINE RESPONSE CAN EASILY BE ACHIEVED WITH OUR PUMA POWER PACK
BUT REAL POWER IMPROVEMENTS CAN ONLY BE ACHIEVED WITH INTERNAL ENGINE
MODIFICATIONS. OUR SUPAFLOW EXCHANGE CYLINDER HEADS PRODUCE UPTO 10% MORE
POWER WITH COMBINED SMOOTHNESS AND FUEL ECONOMY. RESHAPING OF VALVE
THROATS, PORTS AND COMBUSTION CHAMBERS TOGETHER WITH EXTENSIVE POLISHING,
FLOW AIR 42% MORE EFFICIENTLY. EACH HEAD COMES ASSEMBLED WITH NEW SPRINGS
AND VALVE SEALS.
MODEL SHRICK CAM SUPAFLOW HEAD
Mi16 - 1.9 405 £635(pr) £575