Quoting eric:
.... 1720 with accralite forged piston, std conrods, std crankshaft, alloy stage 2 head with stainless valves (39mm and 34 mm), FP 400 springs, Duplex chain, A2 cam (for road use) CR about 10.5.....
Of course I will never have 170 HP but it is not important for me...
But I wonder how much power an alloy head is worth ?