port matching... do it yourself or just buy it and have no real idea if its actually done properly?
cutting the piston skirt some to increase intake duration, which will affect the length of intake required...
direct quote. i really do love mr jennings and his book that im not going to link to here...try google
"My friends at
McCulloch, who acquainted me with the stub-exhaust testing technique, tell of tests they
have performed with an engine having an intake period of 120-degrees, and with pipes
ranging from 5- to 9 1⁄2-inches in length they were able to move the power peak anywhere
from 3000 rpm to 8000 rpm. The 9 1⁄2-inch length gave substantially the same power at
3000 rpm and 4000 rpm; at 5000 rpm, an 8 1⁄2-inch was best; at 6000 rpm and 7000 rpm
the same power could be had with either a 9 1⁄2- or 6 1⁄2-inch length; and the same was true
at 8000 rpm, but with lengths of 5 1⁄2and 8-inches. From these tests, it was determined
that the best compromise length for the entire range 3000-8000 rpm was 8-inches; a 5 1⁄2-
inch length was slightly better for the range 6000-8000 rpm.
It should be understood that
these lengths only apply to this specific example, and would vary with any changes in
intake timing, crankcase volume and intake tract diameter. They are given here only to
illustrate that: A) it is possible to make a given intake timing work over a wide speed
range by varying intake tract length; and
B) that the same length may produce more than
one peak, or conversely that more than one length may be effective at any given power
peak."
read that part B again.
B) that the same length may produce more than
one peak, or conversely that more than one length may be effective at any given power
peak."
did you check the port timings with a degree wheel, and is the exhaust pipe going to suit those timings?
cleaned any of the casting flash from inside the ports, mainly the transfers?
will you try the "stub exhaust" tuning trick for determining exactly what length intake
will suit your particular style?
dont just swallow everything youre told. if you REALLY want to make a drag bike... do some research, get your hands dirty, and over all, experiment! basically...NO ONE has the answers you seek, only YOU can find them, via EXPERIENCE
and who exactly are you racing with, and where? ask some of those people...they already have some experience, sometimes theyll let go of some hard won secrets
oh yeah, and have fun
be prepared to kill a few engines, waste a few dollars... still a lot cheaper than real dragbikes! and safer, too!
