Well, if from Muzzy's, the big block is $2850, and the billet stroker crank is $3700.
All for the sake of an extra 3.7% displacement increase relative to the 1270 from
the boring, and a further extra 3.8% increase from the stroke increase -- which doesn't
necessarily fully translate into equivalent percent increases in hp.
Headwork has always been in the picture, so it isn't a savings of either doing that
or not. I hadn't known about Lee's before this. It looks like their price is about
$800-$1200. I'd been impressed by the results claimed by http://www.cylinderheadshop.co.uk/perftune.html
and still so far am probably leaning
that route for the heads.
The throttle body boring is probably a good idea in either case.
So the cost comparison is really between Lee's cams, vs the billet big block and
crank, or vs combining them all... for sure the first is a big savings!
It's also interesting to note that unlike ZX-12R dyno charts with stock cams, the
Lee's dyno chart even on the pump gas not only is pulling all the way to the limiter,
but actually has peak hp there, the hp curve still climbing, and with the torque not
falling off too badly... this suggests that if the rpm limit could be raised, another
10 hp or so might be found at 12,500 rpm with stock stroke. Which would eliminate any
motivation to increase stroke with the billet crank, as essentially if this is the case,
the stock stroke could produce the same max power as the 60 mm crank, as I wouldn't
spin that crank past 11,500.
However, how do you increase the rev limit, short of going to the Muzzy's ECU? Which
overall I do not want to do.
Anyway, these were the first graphs that made a cam change seem really promising. The
only report I'd seen on a cam change was one over on bikeland, reporting something
like only 3 or 4 hp for the trouble, and with no specific information on how much was lost
at lower revs. With this chart, it was pretty clear that the loss was reasonable. :D
And on the stock bore concept: agreed, stock bore in and of itself should cost no more
than about 5.7% power relative to 1270 due to that percentage of displacement
increase, as a reasonable approximation -- could be a little less or more depending on
whether shrouding is significant and that sort of thing, but this should be close enough.
I myself (unless in a racing application, which isn't the case for me) wouldn't swap
out good 12.2:1 pistons for 13:1. On a thermodynamic basis, which admittedly isn't
the full story but usually is close enough, that 0.8 point increase is worth only 1%. I'd
stick with stock pistons rather than swap out for just that.
So from that standpoint, possibly, the 211 hp on pump gas reported above, could
come out as an estimated 194 hp SAE with stock pistons, figuring 5.7% loss due to
lesser displacement and a further 2% loss from lower compression relative to
the 1270. Hardly bad, and quite possibly enough for 200 mph if say MR9 is used, as
that might give an increase to about 210 hp.
Still, I'd go for the 1270 :D