This is the O.S. Max 21TM Engine with the Revo Manifold. Direct fit for the 2.5 and 3.3 Traxxas Revo. *** Two year limited warranty *** FEATURES: Adapts perfectly to the Traxxas E-Z Start or pull-start systems with no modifications Included manifold is specially designed to fit directly onto the Revo Traxxas' clutch assembly bolts right to the crankshaft with no modifications Oversized cooling fins on crankcase helps to keep engine cooler Three needle slide valve carburetor with fins to help cool the fuel as it enters the engine High-performance long reach O.S. LC3 glow plug suitable for off-road applications that require constantly varying speed INCLUDES: One O.S. Max 21TM Engine with Revo Manifold, LC3 glow plug, 11K slide valve carburetor, manifold spring, rubber exhaust gasket, sticker sheet and instruction manual REQUIRES: Installing in vehicle Air filter SPECS: Displacement: 0.21 cu in (3.4cc) Bore: 0.669" (17mm) Stroke: 0.590" (15mm) Practical RPM: 3,000 - 35,000 RPM Output: 1.8 ps / 29,000 RPM Weight: 8.57oz (243g) Distance between mounting hole centers same side: 0.43" (11mm) Distance between mounting hole centers opposite side: 1.2" (31.4mm) Distance from end of crankshaft to drive washer: 1.03" (26.3mm) Distance from center of engine to front bearing: 1.4" (34.8mm) Distance/bottom of mounting flanges/top of cylinder head:3.2"(81.2mm) Width of mounting flanges: 1.5" (39mm) Length of exhaust flange: 0.24" (6mm) Height/backplate mount to top of cylinder head: 3.3" (85.3mm) COMMENTS: Needle Settings: - High Speed Needle (Needle Valve) 2-1/2 turns out from close. To break-in close approximately 30° after running one tank of fuel through vehicle, repeat five times - Mid Range Needle (Mixture Control Valve) Screw head is exactly 1/2 turn in from flush with the carb body - Low Speed Needle (Metering Needle) Turn 30° clockwise to lean mixture or counter-clockwise to richen mixture