Top Dead Center refers to the piston being at the very top of its travel in the cylinder. Otherwise known as “TDC”.
This position is important when installing a new camshaft, because the cam must be set with the crankshaft at TDC. If the camshaft is off by a tooth, the engine will lack power and risks damage to the piston and valves.
STEP 1: Align Flywheel Timing Mark and Index
Search the outer rim of the flywheel for the T and F marks, in between 2 lines “|T F|”. The line to the left of the T is what we’re after. Rotate the crankshaft so the T line is aligned with the index on the crankcase (as pictured).
STEP 2: Align Camshaft with edge of Cylinder Head
Rotate the camshaft so that the two hash marks and smaller holes are exactly aligned with the edge of the cylinder head.
If your new cam has multiple large holes: Make sure that the “A” number of your cam is visible and rotated away from the engine as seen in the picture.
Or if your cam only has one large hole: On stock cams and some aftermarket cams there is a single large hole in the cam gear instead of an “A” number. In this case, make sure that the large hole of your cam is visible and rotated away from the engine, shown in the red area box below.
Reinstall your timing chain and rotate the crankshaft a few times, double checking the flywheel-to-index and hashes-to-head alignments.