Paul Yaw wrote:

Paul wrote:

Jeff Spitzer wrote:

After I deleted the question recently posted about the timing light a
little light went on in my head.  I think the problem may be that the
wasted spark is fooling your timing light to read double the actual RPM.
Therefore it thinks that the marks are twice as far apart as actual because
it thinks the engine is going twice as fast.  Does the timing light also
have RPM readout?

Jeff Spitzer

As usual, Jeff is on the ball, but there is still a bit of confusion.  A
"dial back" timing light can be used on a rotary rotary fitted with a
distributor if you do a little math.  The dial back is meant for an
engine that has one spark every 720 degrees of shaft rotation.  Since
the rotary has one spark per 360, you have to double the number.  If you
want to dial back twenty degrees for instance, you need to turn the dial
to 40.  If you have a distributorless ign. (86 and later)  you have a
wasted spark on the leading which means a spark every 180 degrees.  You
would have to turn the dial to 80 to achieve twenty at the pulley.  Most
lights only go to 60, so you're screwed.  The trailing ignition is not a
wasted spark configuration, with or without a distributor.  I suggest
removing the pulley, measuring it with a set of calipers, and marking it
every five degrees.  This will allow you to set your timing with a cheap
timing light, and if you mark the pulley correctly, it will be more
accurate.  I found out by accident that dial back lights can vary by as
much as 7 degrees from one to the next.  This is absolute murder to a
13.5:1 small block.  Turned two pistons into swiss cheese, and beat the
hell out of the rod bearings!  If you are willing to spend the money for
an MSD 6A, and an additional coil, you can convert the leading gintion
to a wasted spark direct fire setup which will pay off BIG TIME in power
and fuel economy.  The instruction to do this are here

http://personal.riverusers.com/~yawpower/ignition.html

on my webpage.

Paul Yaw

 
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