Timing mark meaning

Hi Guys

I have a 87 B2000 and was checking the timing for a tune-up. Hopefully this is an obvious question for you experienced guys. There is a single notch on my timing cover and the white and yellow notches on the crankshaft pulley like in the pictured diagram. My question is to set it for the 6 degrees BTDC factory setting, do you just line the white mark with the notch and that is it?

basically, yes....to fine tune it just put a timing light on it and advance/retard the distributor till its on the mark

When those two marks line up, the number one piston is at the top of its stroke. The 6 degrees before top dead center is when the distributor fires the number one plug, it sparks before the piston reaches the top so the explosion peaks when the piston is travelling back down.

The only way to set the timing is with the vehicle running, and a timing light. The distributor is rotated and you can adjust the timing closer or further from top dead center. If you have never broke the distributor loose, its probably right on.

Thanks for the help and clarification. I'm working on it this weekend. It misses a bit on idle and shudders while driving sometimes.

I have 2 Crank Pulley's and neither of them have the white mark. They both have the yellow, no white. The paint is a bit chipped off but the yellow mark is a groove.

is the white mark on a notch like the yellow is?

Some good information and photos here:
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Thanks for posting those links Cusser I forgot about that write up on mazda trucking.