>Just another idea - if the cam timing was off, could that screw up the
>mixture?
>I find this unlikely - afterall, the car does run - but it is something that
>has me worried. It seems unlikely that the cam timing could be screwed up -
>there is virtually no adjustment on a Midget (1500, at least), you just line
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SAY WHAT???
>up the timing marks on the timing gears and bolt the gear to the cam with 2
>bolts. I would sleep a lot better knowing the cam timing is not the cause
>of these problems (I could believe not running if the cam was wrong, but why
>would it affect the mixture? I still think the carb is the culprit...)
>
>Rich Hill
This is the second post in a week about a Spit motor with a new cam not
running right. Time for a little insight into the Triumph way .
The Spitfire motor does not have an indexed cam drive. It is the only
mass produced motor I've seen that is like this. The gear on the cam has
two sets of bolt holes that are slightly staggered. In addition, the gear
can be turned around. This gives a total of eight (!!) different positions
it can be bolted to the cam.
Each and every one of these motors was hand timed at the factory. Some poor
chap sat there with degree wheels and dial indicators, hand setting each
cam. Once the crank and cam postions were set, he would find the best
fit position of the cam gear, bolt it up, then punch a couple of reference
marks on the gears. These marks are valid only for that crank/cam/gearset
combo. If any of these components are changed, the cam timing must be set
again, by hand. This includes installing a new stock cam. There can be as much
as 15 degrees difference one cam to the next. (and, yes, it will still run
with the cam this far out)
The moral is to include a degree wheel and dial indicator in your necessary
engine rebuilding tools list. Merely checking valve rock is not close
enough.
I can't see where the cam timing could cause the mixture to go rich. But,
I can see where it would cause a running problem that could be confused
with being too rich. A rythmic miss/lope, soot out the tail pipe, etc.
The same symptoms as having a cam with excessive overlap, caused by the
intake and exhaust gases not going where they ought to.
Randy
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