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[T3] vacuum and mechanical advance (almost a diatribe)


Yep, Charlie, 
	something is indeed not right.  BUT, it's not the vacuum's fault!  If
you're not advancing with increasing revs, your mechanical advance is
stuck.  It's the set of weights in the base of the dist. that advances
the spark as speed increases.  Either the springs have failed, giving
you max advance, the pivots have worn out (same result) or the points
cam/rotor assembly has corroded to the inner shaft.
	Any which way you look at it, you get to pull the dist. and take it
apart.  Usually, you'll be able to remove 2 or 3 screws around the
outside of the housing, and the base plate (that the points mount to)
will come out.  Underneath this is the mechanical advance- there should
be 2 springs that hold 2 weights close to the shaft.  As this spins
faster, the weights push outward against the springs, and rotate the
cam/rotor assembly a bit, advancing the spark.  Often, people forget
this needs oil (yep, a drop or 2, into the felt under the rotor) and it
can be freed up with some penetrating oil and wiggling...  If there's a
plate blocking access to the springs and weights, you get to remove the
points cam/rotor.  If you're lucky, it's held on with a c-clip, and a
gentle whack on the center of the main shaft will separate it.  I'v seen
a few with e-clips, and they're a pain to get out.
	The other things that can go are the springs- often they just break. 
They're a matched set, so they should be replaced together.  That said,
I haven't found a source!  List?  Jim?
	And on the earlier styles of dist. the advance mechanism itself can
wear out- the pins that advance the cam/rotor wear flats into their
mating holes, which leads to binding and some WIERD advance jumps.  This
is fatal- you'd need a new dist.  I've only seen one this worn, tho...
	The distributor is a complex little mechanism, with some serious
engineering in it, and it needs to be in pretty good shape for you to
get decent performance from your engine...
Toby "learn from your mistakes, you must" B 

> Hello All,
>
> Then, with the light, checked the timing with the vac hose disconnected
> ( it checked fine).  When I attached the vac hose, the timing advanced
> as expected.  But, I accelerated the engine, and saw no more advance
> upon increased RPM.  Is something wrong here?  I thought it should
> advance more.
> 
> By the way,  I have a '67 with stock dual carbs and stock dizzy.
> 
> Thanks,
> 
> Charlie

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