1964 Parilla 250cc Road Racer - 3-Page Vintage Motorcycle Article

Description

1964 Parilla 250cc Road Racer - 3-Page Vintage Motorcycle Article
Original, vintage magazine article
Page Size: Approx. 8" x 11" (21 cm x 28 cm) each page
Condition: Good
One of the most successful machines
in road racing today is the 250cc
Parilla owned by Orrin Hall of Sacramen-
to and ridden by Norris Rancourt. This
combination has won numerous AFM
events in California, with the result that
Rancourt was easily No. 1 in his class
during 1962 and gave an exceptionally
good account of himself throughout 1963.
The Parilla started life as a production
model Grand Sport powered by an engine
designed originally in 1954 and still used
in the latest models. Hall acquired the
machine in 1958 and has been developing
it steadily as a road racer ever since. At
first glance, the machine does not appear
to have undergone much modification and
is decidedly scruffy in appearance, which
belies the painstaking work that has gone
into it. However, closer examination and
a long conversation with Hall soon
brought to light a myriad of detail modi-
fications which, when added together, ac-
count for the tremendous success of the
machine.
The basic Parilla engine is well designed
and precisely executed. The bore and
stroke are square at 68mm and the valves
are driven by a single-lobe, high cam
which operates very short pushrods and
rockers. Hall is most impressed by this
system because he feels that it has all the
advantages of an OHC system without
any of the disadvantages. Enlarging on
this theory, he considers that the valve
mechanism should not be the limiting
factor in any engine, and that many de-
signers overcome the problem by resorting
to twin overhead cams which entail a
complicated, heavy and bulky mass of
machinery sitting on top of the engine.
To prove his point, Hall has a factory
Parilla racer in his shop equipped with a
twin overhead cam head, but he does not
bother to race it because he feels that he
is now getting more usable power out of
his production engine.
Externally, the engine is notable for
the incredible number of holes that have
been drilled through the finning of the
head, and it is reasonable to suppose that
anyone who drilled as many holes in the
outside of the engine has also modified
the inside to a considerable extent. How-
ever, at this point Hall tends to get rather
cagey, but he insists that all the parts
which affect the power output of the
engine are strictly production Parilla items
available to anyone, and the secret of his
success lies in some very minor modifica-
tions and extremely precise assembly.
This is apparently true because the
machine is certainly not in any wild state
of tune and can be ridden as a regular
street machine. It has been set up pur-
posely so that there is plenty of power
throughout the range with a rev limit of
9,500 rpm, but Rancourt normally shifts
at 8,500 rpm which is practically idling
by Italian standards.
By retaining much of the flexibility of
the engine, Hall has lightened consider-
ably Rancourt’s job of riding the machine
on the road racing courses in California.
Most of these courses were laid out for
sports car racing and involve a number
of very tight turns, of the Mickey Mouse
variety, where the drivers of Sprites and
MGs can get down into second gear,
which is apparently most exciting but...
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