The other day one of our readers took the time to drop us a note. He
had seen Kenny Bernstein's Budweiser King Top Fuel dragster light up the clocks
with a 4.60, 318-mph pass. His question was simple: What does it take to build
an engine capable of accelerating a 1900-lb. vehicle from a dead stop to nearly
320 mph in just 1320 feet? I didn't know the answer, but I know a guy who does
- namely "Double-A" Dale Armstrong, the Bud King's crew chief and one of drag
racing's most thoughtful innovators.
Top Fuel racing is unique because there are few restrictions to inhibit
the engine builder. A cursory look at the rule book indicates that only the
displacement, induction system (fuel injector and supercharger), cylinder head
configuration, and electronics come under the National Hot Rod Association's
no-no edict list (some entries, I might add, were the direct result of Armstrong's
legendary imagination).
Unlike every other racing engine, long-term durability isn't a biggie
-- brute horsepower is! Like 6000 pissed-off Percherons at 7,500 (rpm),
or like 5000 Sasquatch pounds of torque at 6000 rpm. "We bleed off far
more launch power than a Pro Stocker makes," says Armstrong, "and we do it
just to keep the 17-inch-wide slicks from losing traction. We burn 58.86 cc's
of fuel 60 times a second at 7200 rpm. And I don't want to hear about a broken
rocker arm slowing down a car. If we break a rocker, the entire engine -- block,
heads, crank, rods, pistons, bearings and blaower -- are, at best, greatly
overstressed, and sometimes rendered totally beyond repair.... they're history!"
History is how this whole "nitro" thing started. Back in the 1930's,
the Germans discovered that when they tickled a Grand Prix race engine's fuel
mixture with a cleaning solvent called nitromethane, it produced a profound
increase in performance. A returning GI brought the nitro secret with him, and
by the early 1950's, nitro had become the "poor man's supercharger."
From a laboratory standpoint, the perfect air/fuel ratio when employing
"pop" is 2 pounds of air to 1 pound of 100 percent nitromethane. So the evolution
of Top Fuel has been one of forcing more and more fuel, and more and more air
into an engine. The secret is how to burn most of it.
"We're probably 1-to-1," concedes Armstrong, "but we want to use the
unburnt 1 pound of fuel as a coolant. Horsepower comes from high cylinder pressure.
However, the tremendous internal heat and cylinder pressure produced by nitro
would melt the engine. For instance, a blown alky motor will produce more peak
pressure than ours -- but it won't continue that peak pressure the entire length
of the power stroke like ours. This is because nitro burns slower than alky
or gas but has a far greater expansion ratio. In fact, it continues to burn
even at bottom dead center (BDC), and there is still a lot of residual cylinder
pressure and unburned gas remaining when we open the exhaust valves. This prolonged
expansion acts to scavenge the unburnt exhaust gasses to such an extent that
the burn is maintained in the exhaust pipes. This is why nitro motors are so
loud."
Burning massive amounts of liquid dynamite forced into a blown Fueler
has been just as revolutionary as using nitro. "We leave the line from a near-dead
idle (2500 rpm) burning 50 gallons of fuel per minute," says Armstrong. "Within
.025 seconds the rpm is up to 8000 before the clutch begins a series of progressive
lockups. At mid-track the rpm is down to 7500, the combustion chamber temps
are up, and volumetric efficiency is increased to the extent that 62 gallons
per minute can be burned. As the clutch fully locks up and the engine begins
to climb to over 8000 rpm, the volumetric efficiency begins to decrease. Fuel
consumption is then 'pulled back' to 56 gallons per minute to keep from dropping
cylinders."
With this in mind, the real stepping stone to 300 mph and beyond has
been making the spark stronger. Two fuel pumps, two barrel valves, three sets
of nozzles, huge ports in twin-plug heads, big blowers, and lots of boost don't
mean diddly squat if the magnetos can't ignite the fuel mixture. For the past
five years, Armstrong has been working on magnetos to produce more of what they
call "joules of energy" at the plugs themselves.
Armstrong was one of the first to successfully employ two magnetos --
he even messed with three but that innovation (along with variable speed blower
drives, and electronically actuated clutch lockup devices) became NHRA no-nos.
First, he messed with rare earth magnets that were more powerful than the ones
contained in the then-current magnetos. He also increased the capacity and altered
the location of the condensors so they wouldn't burn up the points. The net
effect was the first 300-mph run.
Because a Top Fuel engine can be likened to a grenade with a 4.5-second
fuse, its internal components and lubricants must be stronger than a billy goat's
breath. Blocks with huge main webs, chrome-moly studs, billet aluminum main
caps and steel cranks, forged aluminum rods and pistons, cams and valvetrain
components begin to tell the story. These parts must have the capacity to withstand
10,000-rpm runaway speeds when driveline components fail, including oil pumps
generating 200 psi of oil pressure at idle and 195 psi in the lights.
These engines also use a new oil specifically formulated for Top Fuel
racing that's all part of producing the 6000hp act. As for the oil developed
by Prolong to cushion the Bud King's crank, Armstrong swears by the stuff:
"I can't tell you how good it is and how it saved our ass last year."
What's in store for this year is three-fold. Refinements in his engine's
internal dynamics (i.e., different rod lengths and strokes), clutch components,
and control of tire shake lead the list. Even though Kenny Bernstein's Bud King
is king, you can bet your sweet bippy that Double-A Dale isn't going to stand
around and wait for the next footfall -- he's gonna make it fall. Do we hear,
see, and feel 320? How 'bout 4.4? Another Number One? More NHRA no-nos? We'll
keep you posted.
At A Glance
Engine: 90-degree V-8 with 4.189" bore, 4.500" stroke, 497
cubic inch displacement; 40-inch height, 33-inch width, 28.5-inch length;
estimated 6000hp at 7500 rpm; estimated 5000 lbs-ft. torque at 6000 rpm;
$45,000 - $50,000 building cost
Best ET: 4.59 seconds
Best Top Speed: 318.69 mph
Cylinder Block: 8-cylinder Keith Black Stage-X wet style;
4.800" bore spacing; 146-lb. weight; tapered cast ductile iron liners (.175"
top, .165" bottom) honed with 600-grit stone
Crankshaft: Sonny Bryant 90-degree billet steel; internally
balanced with no center counterweights; 68-lb weight; .095" bearings (tin over
babbitt featuring soft material for improved "embedability")
Connecting Rods: BRC, 7075 T-6 forged aluminum; various
lengths in .020" increments (6.981" standard); 890-gram weight; .065" tin-over-babbitt
rod bearings
Pistons: Venolia forged aluminum; staggered compression
ratios from 5.75:1 to 7.5:1 flat-top with intake valve relief; 760-gram weight;
coated with heat barrier and lubricant to inhibit skirt galling from raw fuel;
Dykes top ring; Moly middle; double-rail expander bottom; .028" to .034" end
gap
Piston Pins: Dynamic Machine 1.555" inch full-floating;
332-gram weight; 3.300" length tapered to 1/2" i.d.
Lubrication System: System One wet sump gear type; 22 - 24
gallons-per-minute capacity; 200 psi maximum oil pressure at idle; 195 psi at
finish line; 11-quart Moroso aluminum pan
Cylinder Heads: Alan Johnson billet aluminum; 170cc combustion
chamber; 2.285" by 2.200" intake ports; 1.500" by 2.250" exhaust ports; (13)
9/16" in head, (4) in valley studs; 120-130-lb torque; Clark copper .093" head
gaskets
Intake Manifold: Keith Black magnesium; 22-lb weight; ported
to match cylinder heads
Supercharger: SSI Rootes type; 14-71 with 19-inch long
Teflon-tipped rotors; 40 psi (at the finish line) maximum boost; 25.8 percent
overdrive; 3-inch drive belt
Fuel System: Sid Waterman two-segment fuel pump; 62 gallons
per minute at 8000 rpm; 500-psi fuel pressure; 10 nozzles in injector hat;
8 in intake runners; 16 in cylinder heads
Fuel Injector: 12.5-lb Carbon Speed; three 5-inch butterflies
inlet size with a total of 62 square inches maximum; Pete Jackson barrel valves
