Cannonball Aluminum Cylinder Heads for Knucklehead
Reproductions of Knucklehead style cylinder heads, cast from aluminum. The advantages of this material are obvious: besides the significant weight savings of approx. 4 kg per head, they dissipate heat much better than their cast iron counterparts. That's why the Motor Company implemented aluminum heads on the follow-up Panhead series.
On the down side you have a somewhat lower robustness, which is not really relevant on stock motors, however, when high revs and compression rates, or nitrous and supercharging come into play, well, that’s a different story. So, as always, race oriented riders and their mechanics have to decide which route they would follow.
The design closely matches that of 1940-1947 heads with large intake ports. But technically the Cannonball heads are not just 1:1 copies of the cast iron patterns. That wouldn't work. For a safe operation of both valve seats and guides the manufacturer established additional material around them to securely hold everything in place. Valve seats are pre-installed and sized for stock intake and exhaust valves, but unmachined. They are hardened for the use of today’s unleaded fuels. Steel inserts for the head bolts feature factory threads. The heads show all the small details like cast-in number tags and foundry markings, so they make for excellent stock replacements or for building a performance engine with factory look when you camouflage them with black paint.
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