Hi Russ & Folks, noted your earlier message about the V & H
Harley-sponsored dragbike for NHRA Pro-Stock racing, which is described
in the March Cycle World by Kevin Cameron with his usual mastery.
This IS a very interesting bike, which displays V & H's technical
prowess, building something to the rules that will undoubtedly make that
class much more interesting this year. They can do a lot with a big
budget to make a few racejobs. This is high-class two-valve Hemi
pushrod technology, and interesting they can run 16.2 compression on
race gas in 80 cubic inch(each) cylinders. In fact the article says it
is essential to run such high compression to get the utmost torque for
the essential 60-foot jump from rest.
The article indicates the present designers looked clear back to 1935
Vincent technology to mount the camshafts way up high and run seven-inch
pushrods which I believe from memory is just about the same as the said
Vincent's. Its late designers, P.C. Vincent and P.E. Irving, would be
pleased to know that. This was necessary in the present design to
overcome the limitations of recent Harley clone dragbikes from the very
long pushrods low in the crankcase up to the rocker arms. Supposedly,
especially with long strokers, the rods are so long they whip sideways
excessively unless held to very low lifts.
Another interesting feature of the new V & H engine is that the stroke
is 4-1/2 inches, yet the plan is to reach 9000 revs during a run. A
tremendous piston speed, especially with heavy 4-3/4 inch pistons, and
only possible with extremely strong crankshaft and conrods, and then
only for an instant.
All of this design is interesting, and knowing V & H's past performance,
will probably be successful, but it hasn't, perhaps, much to teach us
because this is such an extremely short-sprint engine for the quarter
mile. For speed trials we have at least a standing mile (ECTA) to run,
and more at El Mirage and Bonneville, so obviously our engines have to
have more endurance compared with a pure quarter-mile engine. It may
be, I don't know, that some bike engines in speed trials are using a
compression in that range (16.2) or they may stay down nearer 13-14 to
1. Perhaps someone who knows will tell us. Cheers, Ardun Bill
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