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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This page was updated Oct. 26, 2024