Chuck---The difference between flywheel HP and that at the rear wheels
can be as much as 18 HP, by some accounts. The advantage in modifying
the engine for more power is that this number is constant, not a
percentage of the total.
To stay away from valve float at the higher revs that can be achieved,
heavier valve springs will be needed for a cam with the duration you are
anticipating. These should be offered by whoever sells you the new cam.
The cam with the 270 duration may not have been upgraded. See if you can
get the combined spring rate that came with this cam from BPNW, and then
ask Richard Good if it's enough spring for the cam you want.
You will also be entering an area where your (stock) pushrods may be too
long, should you shave the head to 10.5:1. (A lot depends on the diam.
of the cam's base circle) Shorter pushrods are available, if necessary,
while some builders just shim up the pedestals.
Consider also adding an Air/Fuel monitor and Oxygen Sensor, to know
'where you're at', carburetion-wise.) A worthy investment when deviating
this far from standard, for about $150.
Dick
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