This is the Ofna Hyper Mach .28 Nitro Car Engine with Pull Start and Rear Exhaust. FEATURES: Six port ABC cylinder construction-"A"luminum piston,"B"rass cylinder liner that is "C"hrome plated Slide Valve Carburetor SG (pilot) crankshaft For increased torque and top-end power engine can be converted to starter box operation by purchasing the Rear Back Plate Cover, OFNG5089 Same mounting dimensions as a .21 cu in engine INCLUDES: Ofna Hyper Mach .28 Nitro Car Engine with Pull Start, exhaust gasket and instruction sheet REQUIRES: Fuel: 10-25% nitromethane content Glow plug SPECS: Claimed Horsepower: 2.8 HP Displacement: .28 cu in (4.6cc) RPM: 38,000 Crankshaft: 14mm SG Carburetor: 8mm Slide Valve Break-in Settings: Needle Valve (High Speed mixture)- 6¼ turns counterclockwise from closed Midrange Needle- pre-set ½ turn counterclockwise (do not adjust) Throttle Stop Screw- About 1mm open from "just closed" position, adjust opening so engine idles smoothly at low RPM without engaging the clutch Distance between mounting holes same side: .87" (22mm) Distance between mounting holes opposite side: 1.4" (37mm) Height from bottom of crankcase to top of cylinder head: 4.25"(108mm) Length from pull starter to front bearing: 3.3" (85mm) Length from pull starter to end of crankshaft: 4.6" (117mm) Length from back of crankcase to front bearing: 2.5" (64mm) Length from back of crankcase to end of crankshaft: 3.7" (93mm) Length from center of crankcase to end of crankshaft: 2.9" (73mm) Width of mounting tabs: 1.7" (44mm) jxs 3/29/06 ir/jxs