Mystery T-Head

By Staff
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Close up of chain drive, igniter actuating shaft and igniter trip mechanisms
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The T-head's camshaft with roller lifters is clearly visible, as is the water pump eccentric on the end of the camshaft.
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The number '29' stamped on the back of the head and block constitutes the only identifying mark on the engine. There's no indication a nameplate was ever fitted to the engine.
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Close examination reveals the four oil lines coming from the drip oiler mounted above the intake.

It seems doubtful that anyone living can shed any light on the
origins of Gene Stewart’s mystery T-head engine. Whether an
experimental prototype or an engine intended for production, its
history has been lost with the passing of time. An innovative and
finely crafted engine, its T-head layout points to engine design
current in the early 1900s.

Engine Layout

In a T-head, the intake and exhaust valves are located on either
side of the cylinder. In the early 1900s this was an innovative
design, and it also led to a cross-flow cylinder; one in which
intake occurs on one side of the combustion cylinder and exhaust on
the other. Cross-flow heads are the norm now, but in the early
1900s a T-head layout was fairly advanced. A downside of the
design, however, was heat dissipation; a problem Gene says this
engines suffers due to the exhaust manifold being cast in unit with
the main engine block. In fact, this engine gets hot enough that
Gene has purposely fitted it with a small fuel tank so he won’t
run it for long stretches at a time.

Gene thinks this engine was designed for marine applications,
and he points to its ‘post’ construction (a construction
associated with marine engines of a century ago) to support this.
In a post engine the lower half of the engine is open and a
separate casting supports the crankshaft. This in turn is fixed to
the upper case by means of posts. This simplified machining and
construction, as an engine could be built up from smaller castings
that were then individually machined instead of the labor of
machining one large casting.

Ignition is by igniter, with one for each cylinder, and that
presented a challenge of its own as Gene brought the T-head back to
life. There was essentially nothing left of the igniters, but
working with what little he had, and studying engines of similar
design, Gene fabricated the igniters sparking the engine. Close
examination shows that each trip on the igniter actuating shaft has
a ramp acting to lift, or swing, each igniter. The ramp drops off
abruptly to complete the process. Looking very much like an
overhead camshaft, the igniter actuating shaft is chain-driven off
the crankshaft and features what’s essentially a sprag- clutch
on the crank to release any tension on the igniter drive should the
engine backfire or otherwise try to run backwards.

With atmospheric intakes valves the engine runs a single
camshaft for the exhaust, somewhat unusual in that most T-head
engines featured dual camshafts with positive actuation of both the
intake and exhaust valves. That would make sense in an automotive
application where engine load and speed can change rapidly. But in
a stationary or marine application load and speed tend to be fairly
constant, allowing a simpler (and cheaper) atmospheric intake
design.

The engine features roller lifters, a design consider high
performance even today. And those roller lifters are interesting,
appearing to almost float in the air; closer inspections shows each
lifter has a pivoting locating rod running to the other side of the
engine to hold the lifter in place.

Other features include steel connecting rods with brass ends,
babbitt main bearings and a plunger water pump driven off an
eccentric on the end of the camshaft. The water pump on the engine
is not original, but it is a period piece, having once done duty on
a 1906 2 HP Buffalo marine engine.

Lubrication is by drip oiler, which is mounted just above the
carburetor. A single, multi-feed oiler supplies four lines; two
going to the cylinder block, splitting inside the block and
supplying drip oil to each cylinder; and two running down and then
splitting off to the connecting rods, providing a drip feed that is
collected by a small scoop on each rod. Crankshaft lubrication is
by splash, excess oil from the connecting rods also dropping onto
the crankshaft.

Cylinder bore and stroke is 2–inch by 5-inch, a typically
over-square design, and Gene figures output to be around 5 HP to 6
HP. Gene has concerns about the engine’s rigidity, so he limits
the engine to a running speed of 150 rpm to 200 rpm. Additionally,
Gene came across the engine by chance some 10 years ago, when he
was one of a few individuals given the chance to buy items from a
collection in California. The owner had passed away, and his widow
allowed a few collectors to pick through the collection before it
was offered publicly.

When Gene bought the engine it was a derelict, sitting outside
unprotected from the weather and, even worse, sitting upside down.
The pistons were full of water and rusted to the cylinders, and
most of the valves had rusted away. But Gene says he was intrigued
by the engine, and decided to buy it and restore it. ‘It was
very unique,’ Gene says, ‘and the challenge was a good one.
I like getting things other people pass over because they’re
too much work.’ It took some time, but eventually Gene got the
T-head in working order. He salvaged the pistons, and with a new
set of piston rings and a few new valves (he used old valves as
patterns) he got the T-head running.

Gene displayed the T-head at the EDGE&TA regional show in
Grass Valley, Calif., this past June, and not surprisingly it drew
a great deal of interest from exhibitors and attendees. A unique
engine occupying a unique slot in the evolution of marine and
stationary engine design, it’s a pity to think we may never
answer the mystery of its origin.

Contact engine enthusiast Gene Stewart at: 4335 Niagara
Avenue, San Diego, CA 92107. Richard Backus is editor of Gas Engine
Magazine.

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