Same cc's more hp?

[D.T.'s]

How does the manufacturer of the same block and CC's make more HP? Does a 60 HP have smaller jets in the carbs than a 75 HP of the same make model? Is the ignition timing altered also in the higher HP, same CC motors?

 

[Dhadley]

Re: Same cc's more hp?

Mostly port timing and higher rpm rating. (Port timing is port location and square area) Better port timing means better scavenging therefore it should flow more fuel. If it'll flow more fuel there's generally bigger carb throats (carb'd motors) or different mapping (injected). Sometimes reed stops are involved.