We've started the 300 hp street fxdr build!
Before we pulled the motor out I thought I would throw some of the changes I had planned to get him the 300 hp from the knowledge I had gained running my Breakout dragbike. This was to fit the SE 64mm Tb, the same intercooler but with bigger bore pipes and a bigger plenum chamber. The result was 270 whp, I posted the results here late last year.
So now we have the new build. This is more about strength than HP. We had seen the 270 whp so to get to 300 a big valve head and maybe a wilder cam, and reduced compression as its on pump gas.
I chose an S & S crank and rods and additionally welded the big end journal, S & S oil pump, a new set of 117 pistons and gasflowing the heads and fitting 1mm o/s valves I had great success running copper O rings to seal the head gaskets in conjunction with Cometic head gaskets. 1.5 mm base gaskets to lower the compression.
What was good to see was that on glaze busting the barrels to bed in the new rings I found the bore was in perfect condition with no distortion or wear on the thrust faces. Good job Harley! I was really impressed by the quality of the Mahle SE 117 pistons, we don't need to go big and have wafer thin sleeves in the barrels, why slog huge pistons creating all the crankcase pressure problems caused buy them. The lovely thing about going supercharged is the engine has an easier time than stock when your not asking for power, lower compression pistons, not huge high comp pistons that are giving the motor a hard time all the time, No huge high lift cams and heavy valves springs. The superb Rotrex design means off load the supercharger takes very little power to turn it, and through its 10:1 step up gearbox and Planetary roller gearbox it can spin to 120,000 rpm with no noise and fantastic power gains from idle.
Below are photo's of the crank, O ringed barrels, piston machining to clear the small end of the conrods.
I am more than happy to hear any comments.
Keep us informed man.












