TDC simply refers to “top dead center.” On all motors TDC can be set on the compression stroke or the exhaust stroke. When resetting or checking the timing on a V8 engine the TDC must be set on the compression stroke. Only standard tools are needed, but you will need someone to briefly bump the engine while you’re working under the hood. Bumping the engine means to just quickly turn the key as if you were starting the engine but not letting it engage and start up.
Locate the number one spark plug on the motor. On Fords the number one plug is on the left side. It is the first spark plug in the front. On Chevys the number one plug is the first one on the right.
Remove the spark plug wire and then remove the spark plug from the head using the spark plug socket and ratchet.
Place your finger over and slightly in the empty spark plug hole. Have your helper bump the engine until you feel the compression cylinder trying to push against your finger. This means the number one cylinder is at the compression stroke. Have your helper stop bumping at this time.
Remove the key from the ignition switch and disconnect the battery.
Place a ratchet and socket on the crankshaft pulley bolt to turn the crank.
Insert a screw driver into the number one hole, but do not let it drop.
Turn the crank while you hold the screw driver. You will feel the piston either coming up or going down. Allow the piston to come all the way up, just until you feel it is ready to drop again. At this point the number one piston should be on TDC of the compression stroke.
