Mechanical Timing (Valve Train)
To check mechanical timing:
Place car in 5th gear ( or 4th :)
Rotate rear wheel CCW ( to maintain correct chain tension)
Have assistant watch #1 piston and indicate when it is near top dead center. (there are various ways to measure exact TDC.. check them out)
Check timing mark on pulley to see if it is at 0°
Check cam sprocket timing chain mark.
Check distributor rotor location
The dreaded chain tensioner terror:
Timing in this photo is at 0° on a 77 280z.
L28 Adjustable Cam Sprocket. It is designed to compensate for timing chain stretch.
- Position one is normal.
- Position two compensates for 4° of stretch OR it advances the valve events by 4° on a new chain
- Position three compensates for 8° of stretch OR it advances the valve events by 8° on a new chain
Most people report that advancing the timing simply moves the peak torque point around. Position 1 has better top end performance and position 3 has better bottom end performance with respect to the rpm range.