Camshaft timing is very critical to the 20R and 22R series motors. With the early motors, the double row chain was very adequate, however, in late 1983 Toyota started the change over to a single row timing chain with plastic guides. It became very apparent that the single row chain would have a greater opportunity to stretch and eventually affect the cam shaft timing. Correct camshaft timing itself is relatively simple to achieve. Find TDC on the #1 piston, set the cam with the dowel pin in the twelve (12) o'clock position, adjust the tension out of the timing chain with the guides (in most cases, this step is unnecessary with a stock set-up) then complete the rest of the installation as required. If you have to degree in a camshaft, you will need as adjustable cam gear, a degree wheel, magnetic base dial indicator and a piston stop. You will then need to follow the instructions supplied with the adjustable cam gear.