This report will
not be your usual Reno air race report, instead it will concentrate
on the unique go-fast features and state of the art engineering
that makes Unlimited class air racing the world's fastest
motor sport. I wish I could also give race results. Alas,
thanks to the despotic acts of the terrorists who did their
evil deeds on September 11, 2001, no races occurred therefore,
no race results.
For 2001 twenty-nine Unlimiteds had entered, These aircraft
ranged from balls to the wall, out and out racers to stock
warbirds. If it were not for the wonderful hospitality heaped
upon me while at Reno I would never have been able to gather
all the neat information incorporated into this report. Pete
Law has been involved with Unlimited teams since the 1960s.
He started his racing career by designing all the systems;
cooling, carburation, ADI and hydraulic for Darryl Greenamayer's
F8F Bearcat. This aircraft re-wrote the rules for the Unlimiteds.
Not surprising considering that until his recent retirement,
Pete was a high level executive working at the Lockheed Skunk
Works. I recently got to know Pete and he kindly took 3 hours
out of his busy schedule to introduce me to every Unlimited
team. Additionally, Pete is a fountain of knowledge on just
about every aircraft, mainly because he probably rebuilt and
set up the carburetor, designed the spray bar system and ADI
system. Others also displayed similar hospitality.
Unlimited racers compete around an 8.2688 mile course marked
off with pylons. The pylons are 55 gallon oil drums placed
high up on a pole. Although no restrictions exist for the
type of aircraft flown, the vast majority of racers are ex-World
War II fighters. This is simply because these aircraft represented
the fastest piston driven aircraft ever manufactured. Of course,
the top racers are highly modified - as we shall see. An argument
that has raged almost from the days of the Wright brothers
first flight is; which is better: air cooled radial or, liquid-cooled
inline. Even to this day, that argument has not been settled.
And perhaps this is the way it should be. The see-saw battle
of liquid-cooled inline vs. air cooled radial will, apparently,
Below is a brief synopsis of each aircraft and the modifications
Race #4 Dago Red - Highly Modified P-51D.
Dago Red is right at the top of Unlimited racing. It has held
the FAI 15 km straight line record at 517.06 mph since 1983
and is presently the fastest qualifier ever at Reno, 490.825
mph. So what makes this aircraft such a phenomenal performer?
This aircraft has been on the race circuit for many years.
It started out as a P-51D Mustang. Registered as N5410V it
was wrecked and rebuilt in its current highly modified form,
and now has been a leading race campaigner since 1982. Hard
to say what percentage of the original aircraft remains but
we can be sure of one thing; it ain't much.
P-51Ds are normally powered by a Packard built Rolls-Royce
Merlin V-1650-7. In stock configuration it is rated at 1,450
horsepower. Dago Red's engine puts out an estimated 3,500
to 3,800 horsepower. And remember, a stock Merlin is no slouch
incorporating features such as overhead camshafts actuating
four valves per cylinder, two stage intercooled and aftercooled
supercharging.....etc. In order for a Merlin to survive at
such remarkable powers, first order of business is to beef
up the basic structure and strengthen it. As is typical with
most V-12 engines, the Merlin features 7 main bearings to
support the crankshaft. In the Merlin's case, the main bearing
caps have additional support by featuring cross bolts that
go right through the engine's crankcase and through the main
bearing caps - one either side of the main bearing hold down
studs. Rigidity of the crankcase and crankshaft is essential
to make the engine survive under high power operation. Therefore,
one of the first modifications is to increase the size of
the cross bolts. With seven main bearings and two cross bolts
per main, a total of 14 main bearing cross bolts are utilized.
As an additional aid to stiffening the entire power section
structure, the 14 cross bolts go through massive external
steel plates that run the entire length of the power section.
So far so good. But all this additional power introduces another
problem not envisioned by Rolls-Royce. The massive four blade
Hamilton Standard propeller is driven through a spur reduction
gear that is housed in a nose case. Of course, all this additional
power is translated into more propeller thrust. In order for
the nose case to stay on the engine, a steel strap attached
to the nose case, bolts to the crankcase inside the intake
valley. Interestingly, this modification may have been inspired
from a repair scheme of World War II. It was quite common
for aircraft to make emergency gear-up landings. With a Merlin
this would inevitably result in a damaged nose case and/or
crankcase (see illustration). Another key item that needs
improving over stock is the lubrication system. A stock Merlin
has a conventional dry sump system and runs 60 to 80 psi hot
oil pressure. Under racing conditions, this is not sufficient.
First off the stock pump gears are replaced with longer ones
to increase the pump's displacement. However, even this is
not sufficient so an additional pump is installed in parallel
with the original pump. Merlins have two accessory drive pads
on the rear of each cylinder head, four in all. Normally,
these pads are used for driving an air compressor, tach. generator...etc.
One of these drive pads is used for the additional oil pump.
An Allison V-1710 pump does the trick. Oil pressure, with
the these modifications now runs over 100psi hot. With all
this additional oil being pumped into the engine, scavenging
becomes more critical. A stock Merlin has a windage tray to
catch oil slung off the crankshaft. An additional windage
tray is installed to improve scavenging. To further improve
scavenging, the vacuum pump is now pressed into service as
an additional scavenge pump. O.K., now we have taken care
of the oil supply and scavenging chores, however, the oil
has now picked up a tremendous amount of rejected heat. A
stock P-51D uses an air-to-oil honey comb cooler mounted in
the so-called dog-house. For Dago Red, this oil cooling system
is totally inadequate. So Dago Red utilizes the P-51H oil
cooling system. In other words, a water/glycol to oil cooler
is mounted in front of the fire wall. Coolant is pumped through
the oil cooler then to a radiator mounted in the dog house.
This offers a far more effective heat rejection route. To
further condition the oil, a sophisticated deaerator is installed
to purge the entrapped air. However, it's not just the oil
that needs to be cooled, the engine coolant, a 50/50 mix of
water and ethylene glycol, is circulated through the engine.
Running at elevated power settings, a stock cooling system
would simply be overwhelmed. It seems that a power setting
of 80 in.Hg. Abs manifold pressure is about all the stock
cooling system can safely handle. To combat overheating, a
highly modified radiator, manufactured by Dave Griswold, is
used. It has more tubes, more fins and more rows. To further
augment cooling, water is sprayed on the radiator core. Water
is introduced via a spray bar system designed by Pete Law.
As Bill Kirchenfaut, Dago Red's crew chief, so eloquently
stated; at race speeds, it's like Niagara falls spraying on
that radiator core. The fact that no after cooler is employed
(see explanation later) allows a larger engine radiator to
be used. The area normally occupied by the aftercooler radiator
is used for engine cooling chores. If one looks carefully
at TV images of top Reno Unlimited racers, a distinctive trail
of steam can be seen issuing behind the aircraft. This steam
is generated by spray bar water that flashes off as it makes
contact with the high temperature radiator core. Dago Red
will consume approximately 60 gallons of spray bar water in
a race, which lasts about 15 minutes. With all these cooling
system modifications, coolant temperature runs at 100 degree
C and oil runs at 85 degrees C. From the foregoing, it can
be ascertained that raising the power of the Merlin is a question
of chasing down all the potential weak points. One component
in a high horsepower engine that undergoes incredible stress
is the connecting rod, possibly one of the most critical of
all internal parts. Stock Merlin connecting rods are typical
of their ilk, they are blade and fork, although Rolls-Royce
took the more difficult manufacturing route of using the 'marine
block' variation on this concept (see illustration). Although
exquisitely made, Rolls-Royce connecting rods were only designed
to tolerate the loads of a stock engine. When manifold pressures
exceed 100 in.Hg. Abs, they become fragile. One of the Merlin's
main competitor's during WWII was the General Motors built
Allison V-1710. Conceptually very similar to the Merlin, i.e.,
liquid-cooled V-12 and similar displacement. Although much
maligned, the Allison was another superb example of aircraft
engine design. One feature in particular that distinguished
the Allison was the stoutness of its connecting rods. As with
the Merlin they were of blade and fork design but considerably
stronger. This hands the hot rodders a golden opportunity.
Although the center distances from the journal to the wrist
pin are slightly different, this can be compensated for by
forging special pistons with a higher compression ratio. The
ultimate Allison series built were the 'G' series and specifically
the G6 series. These G6 rods are the ones installed in Dago
Red's Merlin. One normally thinks of Allisons being built
in the tens of thousands, which is true, however, only 750
G6 engines were built. Their only application was the North
American F-82 Twin Mustang. The available supply has been
further depleted by 50+ years unlimited hydroplane racing
and tractor pullers where they were the favored Allison. For
this reason G6 Allison rods are a much sought after component.
Now that the engine has received structural rigidity, an oil
system and cooling system that can handle the additional requirements
with beefed up internal and external components, it's time
to get serious about making more power. With a highly supercharged
engine such as the Merlin, the easy and obvious route is to
simply crank up the manifold pressure. And that's exactly
what Dago Red does - among other things. It is almost a waste
of time trying to improve upon the intake port design or finish.
In stock configuration, Merlins' were ported and polished.
In service, Merlins' were usually limited, depending on dash
number, to 60 in.Hg. Abs This pressure was preset via the
automatic boost control. In other words, a pilot could push
the throttle to the firewall but the engine would not be overboosted,
but it would not operate at full throttle at sea level either.
So of course the first thing the racers do is get rid of the
automatic boost control. One undesirable by-product of supercharging
is increased charge temperature due to compression heating.
Rolls-Royce took care of this by having an intercooler and
aftercooler incorporated into the supercharger. This simply
means two supercharger impellers run in series to boost manifold
pressure (see illustration). A coolant jacket in the supercharger
housing acts as the intercooler between the two stages, but
it really does not accomplish much. Most of the heat from
compression is rejected via the after cooler. This is a rectangular,
boxy-looking heat exchanger that sits on top of the engine
towards the rear. It is a radiator core with compressed fuel/air
mixture on the outside of the radiator tubes and coolant flowing
though the tubes (see illustration). Works great for reducing
charge temperatures, however, it creates a restriction that
reduces manifold pressure by about 1 in.Hg. Abs. For a stock
Merlin, it's not significant, but for Dago Red's race engine,
running at an astronomical manifold pressure, it's a problem
to the tune of costing approximately 5 in.Hg.Abs. To get by
this problem, a simple pipe replaces the aftercooler. This
now introduces the problem of how to get the charge temperature
down. This is accomplished by introducing massive amounts
of ADI fluid. ADI stands for anti detonation injection. ADI
serves two primary purposes; firstly it reduces the charge
temperature, via evaporation, as it is sprayed into the intake
system. A lower charge temperature increases the density of
the charge and reduces the onset of detonation. Secondly,
once ADI enters the combustion chamber, it reduces the flame
front temperature, again delaying the onset of detonation.
ADI fluid is introduced at the intake elbow, colloquially
referred to as the Horse's Ass because that's what it looks
like..!!! ADI fluid is made up of a 50/50 mix of distilled
water and ethanol or methanol. Engines with the aftercooler
removed are referred to as 'tube engines.' by the racers.
As noted above, stock P-51Ds were typically powered by a Packard
built V-1650-7. However, that was not the ultimate Merlin.
After World War II, Rolls-Royce developed a civilian version
of the Merlin for the more demanding environment of civilian
airliner operation, (long range cruise at high power). Rolls-Royce
toiled long and hard to get some semblance of reliability
and longevity out of the engine. The outcome was the so-called
'transport engine' or more correctly, the Merlin 500 and 600
series. These engines had all heavily stressed parts beefed
up, improved cooling jacket design, heavy duty valves....etc.
Dago Red uses a Merlin 622 power section with a Packard built
V-1650-9 supercharger. The dash nine has optimal supercharger
ratios for increased boost. This brings up the next question;
how much boost does Dago Red run in a race? The quick and
easy answer is; it all depends. During qualifying, only sufficient
power is used to move up to the next round. However, when
it gets down to the final Gold Race, everything is allowed
to hang out. Maximum boost is primarily determined by engine
rpm and secondly by ambient temperature and air pressure.
In this engine it can run in the 135 to 140 in. Hg. range
when at 3400 rpm. Assisting boost is a carefully designed
ram air scoop. For Dago Red it is made from fiber glass with
an ideal convergent/divergent design. This design picks up
approximately 3 to 5 inches of manifold pressure at race speeds.
Theoretically, it is possible to run an even higher manifold
pressure than 140 in.Hg. Abs But at 140 inches the point of
diminishing returns has been reached. In other words so much
power is consumed driving the supercharger, very little, if
any, additional power is fed to the propeller. At 140 inches,
the Merlin two stage supercharger is consuming in excess of
1,000 horsepower to drive. It has even been argued that anything
in excess of 100 inches does not produce any additional power
to the propeller, however the aircraft will fly faster when
running in excess of 100 inches. The argument presented is
the fact jet thrust from the exhaust stacks is increased at
the higher manifold pressure resulting in a higher air speed.
With all these radical modifications, the engine now has to
spin up faster. A stock Merlin is red lined at 3,000 rpm.
This may not sound like much but remember, this engine has
a 6 inch stroke. By modifying the 'speeder' spring in the
propeller governor, Dago Red runs at 3,400 rpm. It would be
nice if the engine could be spun faster, however, engine speed
is limited by several factors; lowest reduction gear ratio
for a Merlin is .420:1 and secondly, propeller tip speed.
When tip speeds approach or exceed 1,000 feet per second,
propeller efficiency goes down hill. In the past folks have
tried to make their own reduction gears with lower ratios
than .420:1, however, this means using a smaller pinion and
a larger gear. The smaller pinion introduces unacceptably
high gear tooth loadings so at the present, this is not an
option (see illustration). Two massive oil jets squirt oil
into the reduction gears at the point of engagement, so it's
not a question of too little lubrication.
All external airframe skins are smoothed out. The so-called
radiator 'Dog-House' (the device which responsible for the
P-51D being able to develop positive 'jet thrust' sufficient
to offset cooing drag, sometimes referred to ad the 'Meredith
Effect named after the RAE engineer who is generally credited
with the concept) is totally redesigned with reduced frontal
area. Interestingly, Dago Red's dog house does not feature
a laminar flow splitter as one would normally expect to see.
A tiny bubble canopy replaces the stock P-51D's. Wing area
is reduced by clipping the wings. The propeller is stock,
albeit highly polished on the front and flat black on the
rear. It would be nice to polish the prop on both sides, however,
this would introduce severe glare resulting in a serious safety
concern for the pilot.
After Monday's qualifying, it was noticed that an exhaust
stack on Dago Red's 'B' bank was smoking. After further investigation,
coolant was found on the center spark plug - a bad sign. The
crew set to and removed the head and bank assembly. Sure enough,
a large crack was found in the center of the cylinder head
that had migrated into the intake port. That head is now an
expensive paper weight, it is unrepairable. A spare head and
bank assembly was installed. For those who have not worked
on a Merlin, this is a major operation, particularly for a
During a 15 minute race, it is not unusual for Dago Red to
consume an astounding 2,200 pounds of liquid in the form of
fuel, ADI fluid and spray bar water broken down as follows:
900 pounds of spray bar water, 300 pounds of ADI fluid and
1,000 pounds of fuel.
Dago Red is owned by Terry Bland and flown by Skip Holm.
Race #5 Voodo - P-51D Modified:
Voodo was a non show this year, however, it is worth taking
a look at. It was intended to race but suffered a catastrophic
engine failure just prior to the races. Voodo has always been
a top contender but to date has been a bride's maid. For 2001,
Jack Hovey built up a special race engine. Time was flown
on the newly rebuilt engine and everything was looking good.
The power was brought up in increments to 90 in. Hg. At this
point the engine back fired. Normally, an engine back firing
is no big deal. But with a highly supercharged engine it is
serious stuff. Backfiring can be caused by a number of factors,
the primary ones being; lean mixture and leaky intake valves.
With Voodo it is thought that the carburetor (Bendix PD-18)
was set up too lean. When an ignition source is introduced
into the intake system, such as a back fire, this lights off
a highly explosive, compressed fuel/air mixture. The pressures
generated from this uncontrolled combustion are so great it
wreaks havoc through the entire engine. Serious damage is
incurred by the supercharger and intake ducting. More seriously
is the fact that this high pressure momentarily blows open
all the intake valves. Allowing high pressure gasses into
the cylinder at the wrong time produces what is in effect
a 'hydraulic lock' resulting in bent connecting rods. Jack
had built this engine with Merlin 622 connecting rods, the
ultimate Rolls-Royce built rods. Voodo's back fire and its
consequent unacceptably high loading on the power section
resulted in bent rods. After the back fire, Matt Jackson,
the pilot, kept the engine running but when he pulled the
power back for landing a connecting rod failed resulting a
destroyed engine. This was too bad as it would have been a
top contender. As an aside, Jack Hovey is one of the more
experienced rebuilders of Merlins. He built the race winning
engine for the 1972 Gold champion, the Roto Finish Special.
A unique feature of Voodo is its use of a carbon fiber cowl.
This represents a weight saving and makes it easier to remove
the cowl. A stock P-51D cowl is a real chore to take off due
to the gazillion Dzus fasteners that have to be removed.
Voodo is owned by Button Transportation and flown by Matt
Race #7 Strega - P-51D, Highly Modified
Strega is right up there with Dago Red for being at the top
of the heap for Unlimited racing. Its engine features all
the modifications incorporated into Dago Red, in fact both
aircraft share a lot of race technology and even look very
similar. One interesting deviation from Dago Red is the placement
of the coolant header tank. P-51Ds have a coolant header tank
that is horse shoe shaped, wrapped around the engine nose
case. In the case of Strega, it is repositioned behind the
pilot. Probably does not enhance performance but makes for
additional room to work on the engine consequently making
maintenance chores simpler to perform.
Flown and owned by Tiger Destafani
Race #9 Cloud Dancer - P-51D
Owned and raced by Jimmy Leeward, a real estate developer
in Florida, little is known about this racer. Its stock looking
appearance may belie some engine modifications. This aircraft
appeared at many earlier Reno events as a highly modified
contender in the Gold Race
Race #10 Critical Mass - Highly Modified Hawker Sea Fury
One of the last great piston powered fighters developed was
the British Hawker Sea Fury. Developed for the British Fleet
Air Arm (FAA), incorporated Hawker's experience learned from
developing a number of high performance fighters in WWII.
Originally, it was powered by the massive and impressive Bristol
Centaurus XVIII sleeve valve engine rated at 2,470 horsepower.
Although this engine was a superb example of aircraft piston
engine development, its uniqueness, particularly in the US,
has dissuaded folks from overhauling them or modifying them
for racing. This has resulted in the vast majority of Sea
Furys' flying in the US being converted to Wright R-3350 power.
Over the years a considerable amount of experience has been
gained on how to make R-3350s perform. Perhaps most, if not
all the credit, should go to Lyle Shelton who has campaigned
a Grumman F8F Bearcat 'Rare Bear' powered by the R-3350. With
this experience in mind, Critical Mass has what is essentially
the same type of engine with the same modifications as Shelton's.
Like many other aircraft engines that remained in production
for a long time, R-3350s went through a lengthy evolutionary
development phase. Starting out with the under developed and
problematic B-29 engines, R-3350s evolved into possibly the
most advanced piston engine in the form of the R-3350 turbocompound
powering such aircraft as the Douglas DC-7 and later versions
of the Lockheed 1049 Super Constellation. Turbocompounding
was experimented with by all the major piston engine manufacturers
but Wright was the only one who managed to get one into production.
Turbocompounding simply means that the exhaust gasses are
utilized to power a blow-down turbine which feeds power back
to the crankshaft. Or, as Wright referred to them as; power
recovery turbines (PRTs). Although the concept sounds great
and in fact it was for large transports due to the considerable
fuel savings it generated, for racing, the PRTs, three per
engine, represent too much weight for too little power gain.
However, the PRT engines also represented the strongest and
best components. Critical Mass employs a PRT engine but with
the PRTs removed. An adapter plate between the power section
and blower section accomplishes this with a weight savings
and reduced engine length. Unlike inline V-12s, radial engines
do not tolerate over revving. Several factors account for
this, one being the extreme loads imposed upon the master
rod bearings. Remember, with a blade and fork rod set-up in
most V-12s, only two cylinders are acting on each connecting
rod bearing big end bearing. A radial, on the other had, needs
a master rod bearing that can withstand the loading of nine
cylinders. With this in mind, Critical Mass races at 3,100
rpm - still a very high number for such a massive engine.
By comparison a stock R-3350-26WD is rated at 2,700 horsepower
at 2,900 rpm. One of the best propellers developed for the
R-3350 was the one installed on the Douglas Skyraider. As
with all the other racers, the holy grail of power and efficiency
is a low(er) revving propeller. Critical Mass accomplished
this via a rare and hard to find nose case. At the end of
the piston engine era, Lockheed developed the ultimate airliner,
the magnificent 1649 Starliner. Although it superficially
looks like a Constellation, it was really an entirely different
aircraft. Wright developed a special engine for this aircraft
called the EA2. It had a very low reduction gear ratio of
.355:1, ideal for driving the Skyraider prop. 287 of these
engines were built, most of which have been scrapped, however
Critical Mass uses one of these hard to find EA2 nose cases.
Again, by comparison, the popular R-3350-26WD uses a less
desirable .4375:1 ratio.
The exhaust system is fabricated from scratch utilizing North
American T-28 parts. A total of 10 pipes are used - five per
side. The outlets are arranged to promote 'air pumping' through
the cowl and residual jet thrust. Critical Mass team members
admitted to 4,100 horsepower; reality may be considerably
higher. Of course, with this amount of potential power on
tap, massive amounts of ADI is used to keep detonation under
control as well as contribute to lower head temperatures.
A stock (Sea Fury) sized spinner is used although made from
carbon fiber. The engine cowl is modified from a Douglas DC-7
component. Sea Furys' use a single rectangular oil cooler
housed in a wing leading edge. For the power generated by
Critical Mass, this would be totally inadequate. To keep oil
temperatures under control, two stock sized oil coolers are
used - one in each wing. To further control oil temperatures,
spray bars are used.
Although the basic airframe is a Sea Fury, little remains
of the stock configuration. The wings are clipped, a new and
larger vertical tail is used and a small bubble canopy replaces
the stockers' larger canopy.
Owned and flown by Tom Dwelle, Critical Mass is clearly a
top contender and in the same class as Dago Red or Strega.
Race #11 Miss America - Modified P-51D
This aircraft has been on the racing circuit seemingly forever.
Its new owner has completely revamped and spruced up this
aircraft although he has retained the beautiful red, white
and blue paint scheme. It's not known how modified the engine
is but does not sound stock. Airframe modifications seemed
to be limited to clipping the wings.
Miss America is owned and flown by Brent Hisey
Race #15 Furious - Modified Sea Fury.
This is another highly modified Sea Fury. Interestingly, this
aircraft is powered by a Pratt & Whitney R-4360-63A. This
highly complex 28 cylinder engine represented the largest
piston engine to enter series production. Its 28 cylinders
arranged in four rows of seven displaced a total of four thousand,
three hundred and sixty three cubic inches. Due to the fact
relatively little racing experience has been developed with
this engine, modifications are quite few. The modifications
seem to be restricted to changing the stock -63A nose case
for a -59 nose case. The reason for this change is; -63A nose
cases use an odd-ball SAE #70 spline propeller shaft. This
means the only propeller available is the three blade Douglas
Globemaster propeller, the aircraft originally powered by
the -63A. So a -59 nose case, used on the Boeing KC-97, replaces
the stock -63A. With an SAE #60 spline the -59 propeller shaft
offers a far better choice of propellers even though the reduction
ratio remains the same at .375:1. Like the R-3350 powered
Sea Fury brigade, Furious uses a Douglas Skyraider prop. The
R-4360 propeller shaft rides in three bearings; a massive
rolling element bearing installed at the front of the nose
case. This bearing handles thrust loads and radial loads.
In the middle and at the rear are two copper/lead plain bearing
that run inside the hollow crankshaft. At race speeds, up
to 6Gs can be generated on the airframe. These tremendous
loads are also imposed upon the propeller. Exacerbating the
situation is the fact the prop acts as a huge and powerful
gyroscope. Of course all these loads are transmitted through
the propeller shaft and consequently transmitted into the
crankshaft via the two rear propeller shaft bearings. These
additional loads require the front main crankshaft bearing
to be beefed up, otherwise it would suffer undue stress. Fourteen
ejector exhaust stacks are used. This set-up siameses appropriate
pairs of cylinders for maximum exhaust scavenging. In a similar
fashion to Critical Mass, Furious uses two stock oil coolers,
one in each wing. Again, spray bars are used to augment the
oil coolers. Spray bar fluid is sprayed at the rate of one
gallon per minute at 25psi. Being air cooled, the R-4360 need
all the help it can get. As with all the top radial engined
powered racers, a beautifully designed convergent/divergent
duct is designed from the spinner and inner cowl. To further
augment cooling, a controversial method is used. But before
going into that, the basic cooling system of the R-4360 needs
to be understood. Unlike single row or double row radials
which simply deflect cooling air from front to rear, the R-4360
is made up of 7 plenums. Each plenum is formed by the space
between each row of cylinders. Cooling air enters the cowl
and is forced into the seven plenums where it is then directed
through the cylinders, almost cross flow fashion. On the leading
edge of the inside diameter of the inner cowl, seven spray
nozzles are incorporated. At race speeds and powers, these
nozzles spray water into each plenum thus getting atomized
water directly on the cylinders. A stock R-4360-63A is rated
at 3,800 horsepower. It would be safe to say that Furious
has in excess of 4,000 horsepower on tap.
Furious is flown by Bill Rogers and owned by Bill Rogers and
Race #21 Modified Hawker Sea Fury.
This stock looking Sea Fury is one of the few race aircraft
to sport military markings. It is painted up to represent
an RCAF aircraft. It is powered by a Wright R-3350-26WD, a
Douglas Skyraider, non PRT engine. As with some other Sea
Furys', it uses a carbon fiber copy of a Blackburn Beverly
spinner. Even though this leaves the remarkably narrow annular
gap of 1.5 inches for air entry into the cowl, cooling is
not a problem. This is accounted for by the excellent design
of the R-3350-26WD cylinder. It incorporates a forged cylinder
head with all cooling fins machined in. The forging process
offers a more structurally sound design without any of the
limitations of a casting. The fins are closely spaced and
deep, thus offering a large cooling fin area. The cylinder
barrel has Wright's patented 'W' finning which, again, offers
considerable cooling area and efficiency.
Race #21 is owned and flown by Joseph Thibodeau. Probably
a good contender for the Silver or Bronze race.
Race #22 Merlin's Magic - Modified P-51D
This aircraft can truly be called a wolf in sheep's clothing.
Belying its stock appearance, except for clipped wings, it
sports a Dwight Thorn, balls to the wall race engine except
it does not have G6 Allison rods. Even though the racers were
just warming up on the last day of flying, Monday, September
10, it achieved its personal fastest qualifying speed at 432mph.
However, it may have been pushed just a little too hard. After
landing, a maintenance check revealed metal in the oil screen
- a bad sign. Rather than risk a $150,000.00 race engine,
it was wisely decided to remove the race engine and replace
it with a stock Merlin.
Owned by Stu and Marilyn Eberhardt, it was flown by Stu and
his son Bill Eberhardt.
Race #27 Miss Trinidad Modified Yak 11
Yaks are now becoming increasingly popular among warbird owners.
This is due to their availability and relatively low cost
compared to, say, a P-51D. The original Russian power plant
is all but impossible to find so most are powered by US built
engines. In the case of Race #27, a Pratt & Whitney R-2000.
Normally, one does not think of an R-2000 as a race engine.
However, when paired with the Yak 11, it makes for a good
combination. R-2000s only powered a handful of aircraft, the
most numerous being the Douglas DC-4 followed by the Canadair
Caribou. Pete Law designed an ADI system for this racer which
allows a manifold pressure of 52 in. Hg. Further helping power
output are ejector exhaust stacks.
Owned by Sam Davis it is flown by Tom Camp.
Race #31 - Stock P-51D (Speedball Allice)
Little can said about this aircraft. Being a stock P-51D,
the owner pilots simply wanted to go racing and have fun.
Owned and flown by Dan Vance and Art Vance.
Race #38 Precious Metal - Highly Modified P-51D
We normally think of P-51Ds being powered by Packard built
Rolls-Royce Merlins. However, the last piston engine mass
produced by Rolls-Royce was an even larger engine than the
Merlin. Displacing 2,239 cubic inches, the V-12 Rolls-Royce
Griffon entered service in the early 1940s. As good as the
Merlin was, it still had some fundamental problems that would
have been difficult to fix once the engine was in production.
The Griffon recognized these problems and benefited from previous
Rolls-Royce experience. Except for the pair of oil lines that
feed the contra-rotating propellers, no external oil lines
are to be seen on the Griffon. The profusion of external oil
lines on Merlins have proved to be a maintenance headache
over the years. Another key change made to the Griffon was
to drive the camshafts from the front of the engine. Likewise,
the single magneto is also driven from the front of the engine.
This reduced the torsional vibration the cam drive and magneto
drive gear trains are exposed to, particularly when driven
for the rear of the crankshaft like the Merlin (see illustration).
The Whittington brothers in Ft. Lauderdale, Florida, originally
modified this aircraft for Griffon power. Engine modifications
follow the same concept as the race Merlins. Precious Metal
uses a conglomerate of parts from different mark numbers of
the Griffon. The power section and contra-rotating nose case
is from a Griffon 58. The two-stage supercharger is from a
Griffon 74 which normally would normally power a British Fleet
Air Arm Fairy Firefly F.R. Mk. IV and N.F. Mk. IV. An adapter
plate is required to mate the 74 blower to the 58 power section.
Like the full race Merlins, the after cooler is removed and
replaced with a tube. All charge temperature issues are dealt
with by massive doses of ADI. Griffon 58s were normally used
to power the Avro Shackelton, a British maritime patrol bomber.
The engine drove a pair of contra-rotating propellers. Precious
Metal retains this propeller and nose case, albeit in modified
form. First off, the propeller diameter is dramatically reduced
and at the same time more pitch is used. The engine runs at
3,200 rpm, stock redline is 2,750 rpm. A modified speeder
spring in the propeller governor allows the higher engine
speed. All stock Griffons used up-draft carburation. Precious
Metal uses a down draft Bendix PR 100 carburetor originally
used on Pratt & Whitney R-4360s. For the Griffon application,
a PR 100 is overkill to the point of being over carburated.
However, this may be due to its prior life as a power plant
for the Miss Budweiser Unlimited hydroplane boat racer. Jeff
Neff, the Budweiser crew chief during the Griffon era, built
three engines for the Whittingtons. One of these engine was
a stocker for ferrying the aircraft. The boat racers used
to turn their engines up to much higher engine speeds than
aircraft racers. In the future, I would not be surprised to
see a PR 58 carburetor replace the present set-up. A ram air
scoop on top of the cowl feeds air to the PR 100. Converting
to the PR 100 carburetor requires the use of an adapter plate
that rotates the intake elbow 180 degrees in order to accommodate
the down draft set-up. An additional adapter plate is required
to mate the PR 100 carburetor to the Rolls-Royce intake elbow.
A modified radiator is augmented by spray bars. As with full
race Merlins, lubrication is enhanced via an additional pump
driven off one of the accessory pads. The Griffon, like late
model Merlins, used what is known as an end-to-end crankshaft
lubrication system. This means the oil is fed in at both ends
of the hollow crankshaft rather than the more conventional
method of feeding oil to the crank via each main bearing.
The advantage with end-to-end lubrication is that it eliminates
the necessity for oil distribution grooves in the main bearings
in order to feed the connecting rod journals. Precious Metal's
Griffon utilizes the additional oil pump to feed extra oil
into each main bearing. Not only does this provide enhanced
lubrication, it also carries away heat thus preserving the
life of the grossly over loaded bearings.
Of course, modifications are not restricted to the engine
and propeller, Precious Metal also has a radically modified
airframe. A small bubble canopy replaces the stock one, wings
are clipped and overall aerodynamic clean up has been done.
Precious Metal is flown by Ron Buccarelli and is owned by
Lake Air Inc.
Race #44 Sparky - Stock P-51D
Little to be said about this bone stock P-51D. No modifications.
Like others in this class, the owner/pilot simply wants have
fun racing around the pylons - and who can blame him?
Sparky is owned Steve Seghetti and flown by Brant Seghetti.
Race #45 Risky Business - Modified P-51D
This aircraft is another wolf in sheep's' clothing. Apart
from clipped wings one would not guess that under the cowl
sits a very potent Merlin. This aircraft is powered by a Rick
Shawnholtzer built race engine. It races at 110 in.Hg. Abs
manifold pressure at 3,400 rpm. The cooling system is augmented
by three spray bars spraying on the radiator core; two for
main engine coolant and one for the oil cooler.
Risky Business is owned and flown by Bill Rheinschild
Race #47 - Southern Cross Modified Hawker Sea Fury.
Powered by a Wright R-3350-26WD; with the exception of the
engine, this is another stock looking Sea Fury. Painted up
in Royal Australian Navy colors, this attractive airplane
was another good contender for the Silver or Bronze. Relying
on ADI, manifold pressure at race speeds is 57 in. Hg. and
2,900 rpm. Two oil coolers with spray bars keep oil temperature
This aircraft is owned and flown by John Bagley.
Race #50 Miracle Maker - Slightly Modified P-51D
This P-51D is absolutely stock in appearance - even the wings
have not been clipped. However, the engine has ADI which allows
a manifold pressure of 100 in.Hg. Abs and 3,200 rpm at race
speeds. It also features spray bars on the radiator.
Miracle Maker is owned and flown by Ike Enns.
Race #66 Fury- Modified Hawker Sea Fury
This stock looking Sea Fury has potential as a fast racer.
Its exhaust system features eighteen equal length exhaust
stacks. The exhausts exit through what appears to be a very
modified cowl. Judging by the design, it is optimized to take
maximum advantage of jet thrust and pumping effect to get
additional cooling air through the cowl. It is powered by
a Wright R-3350-26WD. Race power settings are; 57 - 58 in.Hg
at 2,900 rpm. The engine picks up induction air via a pair
of wing root mounted scoops. This arrangement is a throw back
to the days when it was powered by the Bristol Centaurus.
The Centaurus featured a pair of intakes to the supercharger
located at mid height of the engine. Of course, the R-3350
has down draft carburation so this wing root location is not
ideal for good ram induction. For the future it is planned
to have a ram scoop mounted on top of the cowl. It's estimated
that this simple modification will pick up another 3 in.Hg.
Abs manifold pressure. A carbon fiber copy of a Blackburn
Beverly spinner is used. The resulting annular gap of 1.5
inches is still sufficient to keep cylinder head temperatures
down to a remarkably low 180 degrees at race speed and power.
This aircraft is flown by Howard Pardue and is owned by the
Breckenridge Aviation Museum.
Race #81 Lady Jo - P-51D
This P-51D is a bone stock aircraft painted as a warbird.
Owned by Darryl Bond and flown by Robert Patterson.
Race #86 Czech Mate - Highly Modified Yak-11
In the 1960s and into the early 1970s, Unlimited aircraft
racing was dominated by Darryl Greenamayer flying a highly
modified Grumman F8F Bearcat powered by a Pratt & Whitney
R-2800. This aircraft went on to gain the world's air speed
record for piston driven aircraft. This record has subsequently
been beaten. With the foregoing in mind it is surprising that
more racers don't take advantage of this formidable power
plant. The small and light Yak 11 airframe is ideal for the
powerful R-2800. Little is known about the engine except that
it was built up by Ray Anderson, owner of Day Air, a Pratt
& Whitney overhaul facility. The engine is a commercial
version of the R-2800, a CB 3. It is thought that Czech Mate
may be using some of the go fast modification used by Darryl
Greenamayer all those years ago. What is known is that it
features ADI and a pair of Grumman S2 oil coolers which are
situated behind the pilot. Cooling air for the coolers come
in from scoops on the side of the fuselage under the cockpit
canopy. A reduced in diameter Skyraider propeller is used.
No cowl flaps are used, cooling air is augmented by the pumping
effect of the ejector exhaust stacks. Induction air comes
in from ram air scoops in the wing roots which is then ducted
to the top of the engine into the Bendix PR 58 carburetor
- again set up by Pete Law.
Czech Mate is owned by John & Marcia Moore and is flown
by Sherman Smoot.
Race #87 Miss Merced - Modified Hawker Sea Fury.
This modified Sea Fury sports a spiffy looking flame paint
job. Little is known about this aircraft except it is powered
by a Wright R-3350 and drives a Skyraider propeller. Although
it was intended top race, it was a no show due to an engine
failure after Oshkosh.
Miss Merced is owned and flown by Jim Michaels.
Race #104 Russian Roulette - Yak-9
In the 1990s a number of newly built Yak 9s were made. Hard
to say what category these aircraft would fall into. They
were not restorations and yet it would be difficult to call
them replicas. Made in Russia, they used the same tooling
and manufacturing techniques used to make the originals in
WWII. Even aircraft serial numbers continued on from the last
one built in WWII. The main deviation from the original aircraft
is the installation of an Allison V-1710 in place of the original
M-107, a Russian development of the pre-war French Hispano
Suiza Y series. As a soap box comment; did you ever know of
the Russians coming up with an idea that they did not steal
from some one else? Original engines are now all but unobtainable.
This immaculate aircraft is powered by a Bud Wheeler built
and maintained Allison. To date it is not highly modified,
however plans for the future may include an engine with a
G6 power section and various other modifications such as changing
blower gears to boost manifold pressure.
Russian Roulette is owned by Shawn Carrol and flown by famous
test pilot Dave Morss.
Race #105 Spirit of Texas - Hawker Sea Fury
This stock looking aircraft, except for the Wright R-3350-26WD
engine, has a few modifications worth looking at. It is another
immaculate restoration to come out of Nelson Ezell's shop
in Texas. At race speeds the engine is run at 57 in.Hg. Abs
and 2,900 rpm. It retains the stock aircraft's single oil
cooler. However, the oil cooler installed in this Sea Fury
uses a fin and tube radiator matrix instead of the honeycomb
matrix installed on the original aircraft. Honeycomb radiators
and oil coolers were very common in the early day of cars;
and aircraft continued to use honey comb oil radiators right
up to the end. The honey comb radiator is simply a bundle
of tubes sweated together. Oil flows around the outside diameter
of the tubes and cooling air flows through the center of the
tubes. The big advantage with this type of cooler is the fact
it can withstand extreme pressures, unlike fin and tube radiators.
Although installed on the scavenge side of the oil system,
one would think that the oil cooler would not be exposed to
high-pressure. Under most circumstances, that would be a correct
assumption, however, under cold conditions oil can congeal
to the consistency of gel. This can generate undesirably high-pressures
which, on occasion, can burst a cooler. Nevertheless, Spirit
of Texas has opted to use a fin and tube radiator with its
enhanced cooling capability.
Spirit of Texas is owned and flown by Stewart Dawson.
Race #111 Stock Late Production Yak 9
This aircraft did not appear for the race line up. It appears
to be a stock late production Yak 9 powered by an Allison.
Owned and flown by Brent Hisey
Race #114 Argonaut - Modified Hawker Sea Fury
The Sanders brothers, Dennis and Brian, are renowned experts
in the field of Sea Furys and aircraft restoration in general.
Argonaut is flown by Dennis. It is powered by a Wright R-3350-26W
driving a Douglas Skyraider propeller. This immaculate aircraft
has relatively few race modifications. To keep oil temps under
control, spray bars are used on the oil cooler. Race power
is typically 55 in.Hg. Abs at 2,900 rpm.
Flown by Dennis and Brian (they alternate each year between
Argonaut and Dreadnought) Sanders and owned by Sanders Aircraft
Race #117 Bad Attitude - Modified Hawker Sea Fury
Apart from its Wright R-3350-26W engine, this aircraft is
close to stock. As a concession to keeping oil temperature
under control, spray bars are employed for the oil cooler.
This attractive aircraft is painted up in the colors of the
RCAF. A real Beverly, aluminum spinner is used.
Owned and flown by Bill Rheinschild.
Race #232 September Fury - Modified Hawker Sea Fury
This is another balls to the wall racer designed, built and
maintained by the Sanders brothers. Powered by a Wright R-3350
PRT engine, it has tremendous potential. Unlike Critical Mass,
the other Sea Fury powered by a PRT engine, September Fury
simply installed a PRT engine and removed the PRTs. Whilst
this will work for producing a prodigious amount of power,
their is a size and weigh penalty by not incorporating an
adapter plate between the power section and the blower section.
This engine also retains the direct fuel injection used on
most PRT engines. Two massive nine cylinder fuel injection
pumps are mounted on the 'master control' unit, a mass air
flow measuring device that replaces the carburetor. Fuel is
injected right into the combustion chamber. Pete Law designed
the ADI system (from an early model R-2800 system). Pete also
designed the unique oil cooling system on this aircraft. Rather
than use a conventional air to oil system, Pete designed a
so-called 'boiler system', similar to the one used on Darryl
Greenamyer's Bearcat in the 1960's. Using a massive Douglas
DC-7 oil cooler with 7,000 tubes, it is mounted in the fuselage,
under the pilot. The cooler is immersed in ADI fluid. As the
temperature of the oil increase, heat is rejected through
the ADI fluid and as the fluid boils, steam and gasses are
dumped overboard. ADI fluid is used because of its low boiling
point of 170 degrees F. Although this reporter did not get
definitive power settings, it is safe to say that under race
conditions the engine is operating in excess of 60 in.Hg.
Abs manifold pressure and over 3,000 rpm. Clearly, this aircraft
is another top contender in the Gold battle. A Beverly style
carobn fiber spinner with a 1-1/2 inch annualr gap is used.
September Fury is owned and flown by Michael Brown.
Race #711 Blayak Moose - Modified Yak 11
One would normally think of a Yak 11 powered by a V-12. Apparently
some were powered by radials. Blayak Moose is powered by a
Pratt & Whitney R-2000. It qualified at 332mph indicating
it is a basically stock engine. It does not have ADI - yet.
It is thought that the propeller may be modified from a North
Blayak Moose is owned by Dr. Kent Carlo Magno and is flown
by G.P. 'Sam' Richardson.
Race 911 September Pops - Modified Hawker Sea Fury
This stock looking, except for the Wright R-3350-26W engine,
is a two seat version of this aircraft. The German air force
used a number of Hawker Furys' up to the 1970s as target tugs.
September Pops is, in all likelihood, one of these former
German aircraft. Like several other Furys', September Pops
uses a Blackburn Beverly style spinner made from carbon fiber
resulting in a 1.5 inch annular gap for cooling air to enter
the cowl. It also uses F-104 wheels and brakes. This is another
popular modification that gets away from the original and
idiosyncratic British pneumatically operated brakes. In fact
few, if any, Hawker Sea Furys use the original wheels and
September Pops is flown by Randy Baily and owned by Fury,
A question that often arises is; why don't the top racer use
nitrous oxide. As Bill Kerchenfaut jokingly put it '....we
are already good at blowing up engines, why would we want
get better at it..!!?' With the stresses already imposed upon
these engines, it simply would not be practical to use nitrous
- but it has been tried. Nevertheless, when running at 140
in.Hg. Abs manifold pressure, even injecting all the ADI the
engine can stand will not quell detonation. The next recourse
is to use a high performance number fuel. The top racers are
burning 160PN fuel. Even more exotic fuels such as Triptane
would work even better, but this much desired fuel is no longer
The foregoing synopsis is overly brief. For a thorough description,
each of the top racers could easily fill a book.
One has to admire the professionalism demonstrated by the
owners and crews that work on these ultimate hot rods. Running
an aircraft on the ragged edge of destruction, as many do,
takes skill, nerve, determination and the finest possible
equipment maintained by people who are at the top of their
game. Shadetree tactics simply do not work with these aircraft.
Incredible ingenuity and quality of workmanship abounds in
the pits at Reno. This is what Unlimited racing is all about.