Put together a fresh 370 about a year ago...when it hits the upper mid to WOT there's a rattle that occurs...after several times out, it was taken apart and no sign of piston slap at all...then because of needle clip position issue at Pismo the top-end was bored and new slug was installed with the correct clearances and carb adjustments and again, the same rattle...I swear it sounds like piston slap, but no signs of that at all...all bearings are new, new crank and everything else concerned, no sign of piston to dome contact...timing is at +5 with 110 race fuel, large radiators, Klotz Super Techniplate at 36-1...BDT intake and BDT Werks Expansion Chamber...Has anyone experienced anything like this and/or does anyone have any suggestions??