A View from
Broadway
Nova Rossi Proto Speed head work
Two Nova Rossi 3.5 engines. Ken
Burdick photos.
By Ken Burdick
Let's make yours go faster!
Yes folks, it’s true.
My Nova Rossi .21 is a great engine as is. It has been
modified for Proto Speed in that it uses a marine crankshaft
and runs clockwise to offset the tendency to roll in on
takeoff. This can also be negated by use of a subrudder.
The manufacturer of course has to cover most all
applications and because of this, compromises are made for
reliability and ease of use. Herein lies our focus, lil'
Geezers.
In MY world, I am using the engine to a specific Speed
event, 21 Proto Speed. Proto is a funny combination of fast
top end and good bottom end torque. The first lap plus, it
should be accelerating before reaching its top speed. This
means getting the prop and head combination right as well as
being light weight. These are some of the most important
things to look at. What killed Proto Speed in the 1970s was
use of the tuned exhaust and going for all top end speed.
Non-piped Proto Speed is a great event in it’ challenge of
finding the right combination.
Engine modifications
My shaft timing is left pretty much stock for the need of
good bottom end torque, and the liner is opened up a bit but
timed about stock. Fuel must be 10% North
American Speed Society fuel so they have us penned in,
so to speak.
That really just leaves a few variables such as head,
prop,and weight to get us to the top of the heap.
You are in control of prop and weight, but what about the
head? In the world of two-cycle engines' head design, there
is a much tried and true process called trial and error,
recording changes and noting power difference.
Head spoken here
The clearance from the top of the piston at top dead center
plus the shape and volume of the head chamber is something
that requires much testing and analysis. In our hobby, there
are a few people left who have the knowledge and skills as
well a machinery to produce a very focused head design for
control-line Speed. Henry Nelson, Tim Gillott, John Shannon,
Luke Roy just to name a few. One in particular is a very
soft spoken tool maker who holds many records. He was good
enough to make me a copy of his Nova Rossi .21 head.
For me, this is the difference of running a Proto speed of
125 mph or getting close to the record of 144 mph held by
Jerry Rocha. Jerry is a true master of control-line Speed,
and through the years has shared knowledge when asked. I
have decided to share some of the same.
With help from Tony Huber, I can now share this jewel of
high performance with you. As always, I believe in sharing
"Speed secrets" if it helps promote the sport.
I have contracted Tony to do the machine work, to make five
sets of head chambers, clamps and shims. His work is
exceptional and all CNC. He is the reason the H&R fuel
shut-off works so well in Fast Combat. High standards,
design tools and a willingness to help modelers make this
all possible. So, when it came to who was to make the parts
on this .21 Proto engine, there was no one else that I
wanted.
Five sets of chambers, head clamps and three different head
shims .001, .004, .005. were made.
My engine is a second generation Nova Rossi, four-bolt head
pattern, and that is what these heads are made for. They
also will fit the original black-head Nova Rossi. My
engine will have a head clearance of .005". The engine in
its stock form has a .008" shim so there are a few RPM to be
had by carefully setting the head at .005".
The heads should be arriving in a couple of weeks so I will
begin testing the stock configuration vs this hot rod of a
head. I’ll publish the results right here on Flying lines.
Update:
I ran the #1 Rossi .21 on one of these heads set at
.006"today. I had to run it a few times because the tach
reading seemed too high. The prop is a bench prop that
should simulate air RPM, 5.7 x 6.5, but it's still pretty
darn good.
I used a new tach, but it still seems high. I have sent away
for another so maybe let's just say very high RPM. It
sounded like a siren. When the next tach arrives I'll break
in a new one and then put the high-performance head on it
and compare for another article.
— Kenny-b
Heads and buttons from Tony Huber.
Head button close-up.
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