I just drew a picture of a distributor and a rotor. If you align them
both at TDC, with the window just reaching the photo eye (or the points
just opening) then any amount of advance, from 7 degrees through 35,
will move the rotor end further away from the plug wire outlet thing.
But if you have them aligned when the crank is at 7 degrees BTDC, the
distance between the rotor tip and wire outlet won't be as far as when
aligned at TDC. The shorter path is then achieved by doing the initial
alignment at 7 degrees BTDC rather than at TDC. And even a more direct
path at operating speeds, where it matters more, by doing the alignment
at either a greater BTDC setting.
If I'm missing something here, let me know. I have a Crane unit sitting
on the shelf awaiting installation.
Bill L wrote:
>Hello Phil,
>
> i went thru this.. and tried to get it exactly right, taking a
> few DAYS as i worked only for about 10 minutes at a time and
> thought about what i was doing and what the GOAL was... this is
> MY experience..
>
> when they say align the timing marks .. that is LINE THEM UP!
> TDC! you are calibrating the photo eye's position so that the
> spark would ignite with the shortest distance from the rotor to
> the cap... .. make absolutely SURE that the rotor points is
> pointing DEAD CENTER on the "plug wire outlet thingy" too!
>
> the above step cannot be accomplished without disturbing the
> present timing!!!!!!! your goal is to have everthing LINED
> UP!.. rotor, cap and TDC. can't emphasize this enough!!!
>
> when everything is good there, then slowly rotate the photo eye
> clockwise (since A series engines rotors turn anti-clockwise)
> until you get the "SNAP" from the plug wire. do it a couple of
> times until you are SURE you are just catching the leading
> edge, then tighten everything about the photo-eye securely...
>
> only AFTER you have done these things should you attempt to set
> the timing, either statically, by rotating the whole
> distributor and looking for the snap, or dynamically with the
> timing light...
>
> the car WILL run if the eye is out of place but your ability to
> set the timing could be impaired because the vacuum advance
> unit could interfere with the oil sending unit hose (don't ask
> how i know).. ..
>
> remember the goal is to get the shortest distance between the
> rotor and cap to have the shortest possible spark!
>
> As to WHERE to set the timing, and the effects of cam profile,
> .. these things are beyond my (very) limited knowledge.
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