‘Insiders say there are eight valves – a big deal on a pushrod, aircooled Harley engine’
say the pushrod tubes on each cylinder are parallel, rather than converging as they do on the current Twin Cam engine. That means there are separate inlet and exhaust camshafts – giving a total of three camshafts or possibly even four, all mounted in the block and gear driven from the camshaft.
Normally, four-valve heads are associated with higher-revving, highperformance engines, usually with dual overhead camshafts, while pushrods are linked to thudding motors more interested in torque, and usually with only two valves per cylinder.
However, as engines become larger, the impetus for more valves also grows since they help get more gas in and out of the cylinder more efficiently and offer a better control of that gas flow, in turn improving the way the air-fuel mix burns. As well as improving performance, that gives better emissions – and that’s a big deal, particularly on large, air-cooled engines. It’s not yet clear whether the water-cooled cylinder head idea of the current ‘Twin Cooled’ twin cam engines is carried over to the Milwaukee-eight.
The new engine’s capacity is clearly 107 cubic inches – that’s 1753cc – and given that the engine is new there will be scope for much larger versions for future models. There’s already talk of 117ci (1917cc) or 120ci (1966cc) versions for CVO models.
The engine will debut in Harley’s top Touring models, but expect it to spread to more bikes. The official unveiling will come at the end of August, when Harley’s 2017 line-up is launched.