Greg---I recall you are the fellow who wanted to try getting the early
cam timing low end "advantage" while using the later style cam. (?)
It's a given that doing this will compromise other parts of cam timing,
but I'll try to clear up some of the numbers here, at least so far as
how many degrees of changes occur with each sprocket tooth.
There are 21 teeth on the crankshaft sprocket, so jumping the chain
one tooth would be 360 deg./ 21 or 17 deg., (dropping the fraction)
There are 42 teeth on the cam sprocket, so again jumping one tooth
will be 360 deg./42, or 8.5 deg. per tooth.
We know there is an alternate pair of bolt holes in the cam
sprocket, allowing the timing to be further adjusted to four deg.
increments.
While four deg. may not be close enough to what you want, what it
really means is that you should never be off from what ever you are
shooting for by more than two deg., as you could be either two deg.
advanced, or two deg. retarded from a "0" deg. ideal. (Or some combo
thereof)
There are those who will say that it makes no difference whether you
jump a tooth on the crank sprocket, or a tooth on the cam sprocket,
because a "tooth is a tooth". I might be convinced of this if it could
be explained to me. For now, I believe that a finer adjustment can be
made at the cam sprocket.
Now, more to your original question... I'm not sure why you are looking
for a different sprocket that gives a 7 deg. offset. If that's the cam
timing you want, you could just advance or retard the cam sprocket to a
tooth orientation that gets you closest to it, using the double row
sprocket you now have. For future reference, scribe a new line once you
are satisfied.
If you want to split hairs here, you could make a crank sprocket key to
get you even closer to the number you are looking for. Start with 5/16"
key stock. Mill off, say, 1/16 inch on opposite sides so it fits like
the stock 1/4 inch key. (You'd have to do the math to know how much
you'd need to alter to make this off-set key)
There is also eccentric cam sprocket (bolt) bushings, but unless you
made them yourself, you would be adding to the expense that you are
trying to avoid.
Dick
From:
rgperry@earthlink.net(Greg Perry) Date: Sun, Hello,
Has anybody advanced the late TR6 camshaft (7 degrees) timing to the
early TR6 camshaft timing with the original cam gear? Basically
advancing one tooth (7 degrees) on the stock cam gear. I know that I can
spit a tooth (3.5 degrees) by using the other set of holes on the stock
cam gear. Is there another stock double row cam gear for a different
application that would be marked one tooth advanced? The Vernier cam
gear is a little pricey for me.
Thanks,
Greg Perry
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