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markjenn markjenn is offline
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Join Date: Nov 1999
Location: Bellingham WA
Posts: 3,603
Originally posted by Bob Hancock
If you think about it some, the area on the back side of the cam is pretty wide, so being within 5 degrees either way is good enough and the sprocket mark set at 3 or 9 o'clock is just fine.
I don't know the precise cam timing, but the intake and exhaust valves are closed for about a full 360-degree crank rotation so trying to get to within even five-degrees is probably unwarranted precision. Doesn't hurt a thing, but probably unwarranted.

On shim-adjusted valves I do always set the engine at a precise TDC point for consistency; I don't want to risk the extra work of swapping a shim just because a borderline valve has gone out of spec due to my setting the engine as a slightly different spot and chasing the variations in the cam base circle. But on a BMW with screw/locknut adjusters, where adjusting is just a minute or two extra vs. checking, I don't worry about it and just get it close to TDC using a soda straw in the spark plug hole.

- Mark
Old 07-06-2007, 09:42 AM
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