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There are 2 different timing events, you have valve timing, and you have ignition timing.
The cam position relative to the crank sets valve timing, which determines when the valves open based on crank position. With the timing dots lined up #6 is at TDC compression and the dowel pin will be to the right. The cam gear turns 1/2 speed of the crank so 1 revolution at the crank moves the cam dot from 6 to 12oclock which is #1 compression, and the dowel pin will be on the left. Thats why it doesnt matter whether the cam gear dot is at the top or bottom, because either way the vavles are tied to the crank rotation the same way.
Ignition timing sets the distributor relative to the cam position as well as the crank since they are tied together and determines when the spark occurs based ultimately on crank position. Like the previous poster mentioned, you can do this on any cylinder but #1 has in effect become the default. But if you had a marked balancer and bring #3, (or #2 or whatever) to TDC on the compression stroke, you can stick your distributor in pointing to that cylinders terminal in the cap and get the same end result. You can also set timing with a light off of any cylinder if you have a degreed balance at 90* intervals, just follow the firign order through 90* steps to know whether you should be reading at the 0 90 180 or 270 degree marks.
The cam position relative to the crank sets valve timing, which determines when the valves open based on crank position. With the timing dots lined up #6 is at TDC compression and the dowel pin will be to the right. The cam gear turns 1/2 speed of the crank so 1 revolution at the crank moves the cam dot from 6 to 12oclock which is #1 compression, and the dowel pin will be on the left. Thats why it doesnt matter whether the cam gear dot is at the top or bottom, because either way the vavles are tied to the crank rotation the same way.
Ignition timing sets the distributor relative to the cam position as well as the crank since they are tied together and determines when the spark occurs based ultimately on crank position. Like the previous poster mentioned, you can do this on any cylinder but #1 has in effect become the default. But if you had a marked balancer and bring #3, (or #2 or whatever) to TDC on the compression stroke, you can stick your distributor in pointing to that cylinders terminal in the cap and get the same end result. You can also set timing with a light off of any cylinder if you have a degreed balance at 90* intervals, just follow the firign order through 90* steps to know whether you should be reading at the 0 90 180 or 270 degree marks.
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