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October 26, 2003
Well...
Sounds to me like you've got ignition
timing mixed up with cam timing.
The cam timing can be "staight up" or
for a little heftier lower range at minimal
expense to the top end, timed in no
more than 4 degrees "advanced" per
Vizard's recommendation. Assuming you
are using a new timing chain, after
initial chain "stretch" the cam will end
up running 2 degrees advanced...perfect!
For your application considering a small
bore engine, and "long stroke" at that, I'd
go "straight up" for the track, 4 degrees
advanced for the road, most especially
if you're planning to run it in any sort of
traffic situation.
Ignition timing (and glowing headers indicate the ignition timing is
currently
set "retarded") should be stock, with no
more than 34 degrees total (set vacuum
advance dis-connected and any open
port on the carb. capped off for this
adjustment). Considering the cylinder
filling (torque) curve of the VP3, less
total timing will be more the name of the
game, here.
You might find the engine torquier from
mid-range, up, with less total advance...say 30 degrees. Of course, if
this is the case, it will come at the expense of low end torque,
considering
you might have to retard the whole works
to run this degree of advance. Maybe, maybe not.
An Aldon "Yellow" curve would be just
the ticket for a hot street cammed motor,
Martyn.
It has a fairly soft in initial advance spring
so as to advance the timing quickly to
set the spark off "early" in circumstances
wherein cylinder filling is relatively less
(low end and bottom mid-range) and
"strong" secondary advance spring to slow
the rate of advance in the upper rpm range, wherein cylinder filling
increases
(the rpm range whereing the cam "comes
in strongly) per the torque curve of the
VP3.
Otherwise, set the stock distributor as to
stock spec. Just make sure the total advance does not exceed 34
"mechanical"
degrees and you are using the highest
octane pump unleaded available.
After you've done this, re-connect the
vac. advance for better fuel economy
under light load cruise conditions.
Cap'n. Bob
'60 :{)
PilotRob@... 26327
Posted on October 26, 2003 12:05 PM
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