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 Posted: 11-08-2016 03:32 am
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
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Screenplay wrote:
I also have a question: My current project, #18341, has a timing belt that rides near the rear edge of all of the toothed gears - cams and oil pump/distributor drive. Yet on other cars the belt rides in the center of the gears. Does anybody know why? Any thoughts on this?Belt tracking wasn't perfect in the beginning, but it wasn't far off. In the late 1970's ('79 ?), while 'metricating' the engine, Lotus modified the hub's width to better center the pulley's position under the belt's track.

But that's a small thing. If the belt is tracking way off center, then that does indicate that some shaft is off-axis somewhere... but there isn't just one scenario. It can be the tensioner bearing stud, as mentioned, but the cams are the more common source. Everything was pretty straight & true from the factory, but if the head has ever been milled to 'fix' a warp, then it's not uncommon for the new surface to not be parallel to the cams.

Also, when a head warps, the whole thing goes banana shaped, not just the bottom face. Truing the bottom doesn't straighten the top, and the cams may go cross-eyed.

Similarly, if the block has ever been decked or align-bored, it's possible that axis alignment was lost somewhere.

If the belt is running off the edge of the pulley, then that's a problem. But if it's just running a little off-center, but still on the pulley, don't sweat it. It's okay.

Regards,
Tim Engel