Question on the known power gain to a 2hp head swap on a 3hp?

old shed finds

Well-Known Member
#1
Had these both torn down and the heads look identical? A 2hp and 3hp 'on the bike'..
There is a rumor that we can get a power gain of swapping a 2hp head on our 3hp...? Have I got two 3hp heads? Is there stamping on a 2hp head to identify it?
 

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old shed finds

Well-Known Member
#4
There is a number cast into the top of the head (between the fins). This number is the displacement 6 = 2hp, 8 = 3hp. Using a 2hp head on a 3hp motor is supposed to increase compression. Some folks say the reduced flow offsets any gain in compression. The debate continues.
Richard you are always right.. found the cast and both are 8 so now the fun goes on for a cast 6, 2hp head...
 

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