Engine, or crankshaft rotation, is the direction the engine spins: either clockwise or counterclockwise. Most vehicles have the standard rotation, counterclockwise. Only a few vehicles, such as early Hondas and the American-made Chevrolet Corvair flat-six, had reverse rotation, or right-hand spin in a clockwise direction. If you want to determine the turning direction of an engine, there are a few things to look for.
Things You'll Need
- Owner's repair manual
- Floor jack
- Jack stands
- Socket set
- Ratchet wrench
- Screwdrivers (if applicable)
Look up your vehicle engine size and statistics in an owner's repair manual for the exact make, year, and model of your vehicle. Engine rotation -- either standard or reverse -- will be listed under engine statistics and performance. Chances are good that your engine is standard and rotates counterclockwise.
Raise the hood of the vehicle and disconnect the ignition coil wire from the coil or coil pack. Put the transmission selector in neutral or park, depending upon your transmission type. Set the emergency brake.
Raise the vehicle with a floor jack and place two jack stands under the rear frame and two jack stands under the front frame.
Use a socket and ratchet wrench to remove the inspection cover of the flywheel. Use a screwdriver if screws hold the plate to the housing. Check your owner's manual to see if your inspection plate sits on the top or the side of the engine (unique to your make, model and engine placement) and remove it with a socket or screwdriver.
Instruct an assistant to "bump" the starter over, to rotate the engine. Watch the rotation of the flywheel from the rear. If the flywheel turns counterclockwise, or left-handed, it denotes a standard rotation. If the flywheel turns clockwise, or right-handed, it signifies a reverse rotation engine. Remember that if the front of the flywheel shows through an inspection plate, reverse the rotation to account for the flywheel as seen from the rear.
Stand in front of the engine, facing the pulleys. This applies to an inline or side-mount engine. Have an assistant bump the starter motor so the pulleys and belts move from the crankshaft rotation. This procedures works if you cannot see the rear or front of the flywheel anywhere on the engine. Note the rotation. Pulleys that move clockwise have left-hand rotation, and pulleys that turn counterclockwise have right-hand rotation.
Tips & Warnings
- Marine engine rotation is calculated by using the same measures as an automobile engine, except where dual engines exist. The port or right-hand engine will normally rotate in a left-hand, counterclockwise direction, denoting it as the standard rotation engine. The starboard engine will rotate in the opposite direction to offset and neutralize the torque of both propellers. Yet the starboard engine will rotate opposite the port engine due to the inclusion of a reverse direction gear, which is an added component.
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