20/2 Cam Timing

[akghound]

I had much confusion in setting the valve timing today, even though I have done it several times. Having some kind of mental block I was mistakenly going off TDC of the power stroke not the intake stroke. 
So engine rotation goes;
TDC – Piston starts down on power,
BDC – Piston starts up on exhaust stroke.
TDC – Piston starts down on intake stroke. This is where the measurement is taken. Today it is .045 inches off of Dead Bottom. Dead bottom for the valve cam lobes occurs when the fuel cam is between 9 o'clock and 12 o'clock. The general area for the fuel cam lobe should be near the 5 o'clock position when the engine is properly timed. At this point the exhaust is closing, almost closed, and the intake valve has just started to open. I still think the timing window is broad, something like .040" to .050" depending on the individual engine.
BDC – Piston starts up on compression stroke.

Be sure to have both of the cam cover housings in place when taking the measurements to time the cam.

Ken Gardner

[Wizard]

More precise of TDC is shim the one valve down a bit as piston stop, bolt a bent wire on as pointer to the flywheel at the edge or just over it and slowly rotate flywheel one direction till it is impreded, mark it at that tip of that wire, rotate other way till stopped, do the same.  Exact half-way between that markings is your exact TDC.  Do a formula work on injection point in degrees into inches based on your exact diameter of your flywheel and plot this new mark from that TDC mark.  Now that's your injection point/spill point to set up the pump.  That's for particular cylinder.  For second cylinder, need to do same job for new injection point with same pointer (do not move it, till both injectors set up is done.)

Cheers, Wizard