A NEW GENERATION RACE ENGINE
In the Hi Performance Industry, and specifically in the drag racing circles, the name Joe Schubeck may sound familiar, especially to those of you who have been around for a few decades. He was the founder of Lakewood Industries in the 1960s, which was well known for the Lakewood Scatter-shield.
The rapid business growth of Lakewood forced his early retirement from Top Fuel drag racing in the late ‘60s, but that did not dampen his desire to stay involved. He especially had a keen interest in the, “hemispherical head”, Chrysler engine that he raced. The “Hemi”, as it is called, was, and still is, the engine of choice throughout the upper classes of drag racing, for the last forty years.
In the 70’s, after selling Lakewood Industries, Schubeck formed Stage II Development Co. Stage II's mission, was to adapt the Chrysler Hemi engine to Crop Duster airplanes, replacing the under powered radial engines, built during WW II. Among the necessary parts, needed to make the engine airworthy, were cylinder heads with two spark plugs per cylinder. (The Federal Aviation requires independent ignitions, firing two plugs in every cylinder, for all internal combustion engines.) It was with his new dual plug cylinder heads, that he made a significant contribution to drag racing by introducing these, dual plug “Hemi” heads to his former competitors. It didn't’t take long before the trend caught on with all the competitors in the dragster and funny car ranks.
With Stage II Development Co. supplying it's dual plug aluminum heads and other West Coast companies producing aluminum blocks, the re-manufactured engine soon became a total aftermarket replica of Chrysler Corp’s engine. One company after another leapfrogged onto the bandwagon to supply parts for an engine that never seemed to wane from popularity. Soon there was nothing left, in the way of engine parts, that needed to be bought from Chrysler. It seemed everyone was locked into a design that had roots in engine technology of the 1950’s.
The Hemispherical combustion chamber design was sound but the valve trail had it limitations. This became more apparent when blower pressure and nitro methane was added to the formula for increasing power. More critically, the Hemi’s valve train is stressed beyond the levels it was ever meant to endure. Valve train failure frequently lead to catastrophic engine failure (blower explosions are the example). As the engines were fed more blower pressure and nitro methane, structural weaknesses in the block became apparent, even with the aftermarket aluminum replacement blocks.
Shortly after Schubeck sold his Stage II cylinder head business, he formed the Eagle Engine Manufacturing Co. in 1986 with partner, Steve Barber. The purpose of the new company was to develop and produce an alternative, blown fuel engine, for dragsters and Funny Cars.
The goal was to design an engine that could be worked on with the least amount of hassle—an engine that was, in effect, user-friendly.
Another goal was to make as much power as a Hemi, but to do it with less strain on the valve train, which led to the decision to use double overhead cams and quadruple valves. Schubeck believed that the Eagle would cut back on the stress to save parts while not giving up any power in the process.
To say that this was an ambitious project, was a bit of an under-statement.
Heading up the program, Schubeck hired the services of Joe Anahory, a respected design engineer, with experience in engine block design for the Blown Fuel category, for several different companies.
Starting with a fresh sheet of paper, Schubeck’s plan did not have to work around the parameters of an existing engine. In fact, it opened the door to use current engineering and manufacturing technology to develop a completely different engine. The best of the European and Japanese, double overhead cam (DOHC), four-valve head technology was combined that with an American-style, large displacement block, using newer and better methods to support the loads developed in this arena of racing.
How the Eagle team accomplished this task, but never saw drag racing competition, is an interesting story.
After a “blitz” development program that had even some auto company execs. scratching their heads. Schubeck was well into the final phase of dynamometer testing in just thirteen months, when news of the engine reached the West Coast branch of a prominent international conglomerate. The Canadian company’s development team was designing a high performance luxury vehicle, in total secrecy, only a few miles from where the Eagle was being developed in Westlake Village, Ca.
The vehicle, a four-wheel drive, all-terrain, luxury, utility, ATV was planned with hopes to exceed 200MPH, if enough power could be packaged under its hood. This is where the intended, Mercedes V8 engine, fell short.
It didn’t take long, after seeing a moderately conservative, 500 cu. in. Eagle prototype, producing in excess of 750 horsepower, on the dynamometer at 5200 rpm, before the company made a bid for an engine and soon after, for the rights to the whole company. Schubeck and Barber were made an offer they couldn't refuse. Schubeck stayed on as overseer of engine production and within months, the six million dollar, Eagle powered, prototype car was introduced at the World Auto Show in Geneva Switzerland.
At a press party, the CEO announced that the company would produce two hundred of these special vehicles called the “Torrero”, in the first year and the selling price would be $185.000 US.
Making a long story short, Schubeck’s drag racing program got completely sidelined with bigger plans for car production. Engine production for the car was the first priority, but Schubeck envisioned the spill-over effect could make some engines available for racing somewhere down the road. That never happened, because as it turned out, plans for car production had to be canceled for economic reasons. What seemed like a dream come true, went up in smoke with one simple stroke of an accountants pen. The company was closed and the engine was tied up in corporate red tape for the next 10 years.
Soon after, the N.H.R.A. outlawed participation of any new and innovative engines for dragster and funny car racing. Schubeck went on to develop other ideas he had for new products that would sell in the high performance aftermarket.
The new company, Schubeck Racing Engines & Components, once again, owned jointly by Joe Schubeck and Steve Barber, was initially formed to produce high performance valve train components for drag and oval track racing. Only recently, the company began a new development and is now producing, an entire new engine based on the Eagle technology. The all new, Schubeck 904, was expanded to house a larger cubic inch displacement, as the name depicts. Along with the hefty displacement increase and other improvements, such as the hydraulic valve actuators, that eliminate the need for adjusting the valves, the 904 is basically a larger, but more refined version of it’s predecessor, the Eagle engine. The new company is located in Las Vegas, Nv.
The 904, high torque engines, are designed to produce twelve hundred horsepower, without a supercharger, burning low octane pump gasoline. The development of this normally aspirated engine, is aimed primarily at the marine cruiser market.
To best way to describe the 904 engine and its qualities, would be to continue on comparing it to the engine that it’s predecessor, the Eagle, was designed to replace in Top Fuel drag racing, back in 1989, the “Chrysler Hemi”
The comparison to a Chrysler "Hemi" engine
A MORE RELAXED VALVE TRAIN
We will begin with Schubeck’s reasons for going to the seemingly complex, yet inherently superior, double overhead cam/four valve per cylinder design were numerous and go far beyond the previously mentioned stress factor.
Firstly, when it comes to airflow, more valve perimeter is definitely better. The four-valve head will flow much more charge into and out of a cylinder than will a two-valve of equal cylinder size. The quad-valve head has 65 percent more valve surface area than a Hemi while, just as important, there is 63 percent more area on the exhaust side. (The capability to purge the cylinder of exhaust gases more efficiently is the seldom-seen weak link in the power producing ability of the Hemi, or any engine for that matter.)
Secondly, the Hemi valve train can be described as nothing short of tortured. The reciprocating (back and forth) valve-train mass presents a severe strain on the ability of the engine to stay together and, if it does, to reach its power potential.
Conversely, the DOHC, four-valve design is a relaxed system because less energy is going into the spinning of the valve train. With the elimination of push rods, lifters and the positioning of the camshafts above the valves, the valve train is shortened and lightened.
One result is that valve spring pressure can be reduced drastically. On a typical Hemi, the intake valve runs with 220 pounds of closed seat pressure on the intake valve spring. On the new Schubeck engine, the closed valve spring pressure is 110. That represents a 50 percent reduction of spring pressure on the valves. When the valves are open, the Hemi spring pressure measures between 600 and 700 pounds, compared to 280 pounds open. Reduced spring pressure translates into fewer fractured valves and fewer broken valve springs.
Another benefit of the lessened spring pressure and the lighter valves is that the valve train will last longer at the same rpm, or it will live the same amount of time at a higher rpm. And because two small valves are stronger as well as lighter than one big valve, they can stand higher acceleration rates. The reason? Apart reduced in size will lose weight faster than it will lose strength. Not only do two smaller valves expose greater flow because of a greater perimeter, but they can be opened faster, which doubles the advantage.
Thirdly, with the greater flow efficiency of the valves and the relaxed valve train on the 904, the cam timing is less radical. Because the 904 exposes the air/fuel flow to the cylinder 1.5 times faster than a Hemi, the cam duration can be backed off. Also, the increased valve area allows for the lift to be less than that of the Hemi. The lift on a Hemi runs almost .800-inch, while the Schubeck 904 has to lift only about .550-inch.
Two intake valves are inherently better than one for two simple, yet crucial, reasons. Two valves expose a greater amount of intake flow to the combustion chamber and they do that at a faster rate than a single valve. For two chambers of equal size, two intake and exhaust valves will have a greater circumference than single intake and exhaust valves. The valve circumference—the valve “hole,” if you will—determines the breathing capacity and, hence, how much power the engine can potentially produce.
To get specific, the distance around a K. B. Hemi intake valve is 7.224 inches (the valve’s diameter of 2.30 inches multiplied by pi, or 3.141). The distance around a single Eagle engine intake valve is 5.496 (1.75 inches multiplied by pi). Multiply 5.496 by two and you get 10.99 inches of total intake port area per cylinder (one inch short of a foot of surface area!). Therefore, the Eagle engine has 3.77 inches more intake port area (10.99 minus 7.22) to flow the charge. That works out to a whopping 65 percent more surface area than a K-B. What’s more, it flows the air/fuel mixture 1.52 times faster than a K-B head (10.99 divided by 7.22).
Work the numbers on the exhaust side—1.94-inch exhaust valve for the Hemi and 1.50-inch exhaust valve for the Eagle—and it comes out that there is an equally impressive 63 percent increase in surface area. That dramatic increase in exhaust capacity is almost as important to making more power as is increasing intake capacity. A polluted intake charge robs the power potential of a nitro motor—a given volume of exhaust gas not able to exit the cylinder actually displaces that much intake charge trying to get in.
Although a 65 percent increase in valve circumference does not equate to a 65 percent increase in actual flow, the real-world advantages of the four-valve are clearly superior to a two-valve motor. After all, figures don’t lie.
PENT-ROOF CHAMBER
The 904’s combustion chamber design is very unique. Because the use of four valves allows for less valve angle, the geometry of the combustion chamber changes dramatically. In the 904, the chamber has a pent-roof design as opposed to Hemi’s classic dome shape.
The chamber of choice of the Japanese “super” bikes (the Kawasaki Ninja, the Honda Hurricane, the Yamaha FZR, etc.) and Indy and Formula 1 engines, the pent-roof permits a flat (or even concave) piston, a cylinder head that is only slightly domed, and a centrally placed spark plug. The effect is that the fuel and air mix are ignited rapidly because the mix is concentrated tightly around the plug. That allows higher compression ratios to be used with less fear of dreaded detonation—the charge quickly burns before the detonation. There’s another benefit of the pent-roof design. Because the mixture is inflamed quickly, heat loss to cooler parts of the head is cut down so more energy is available to push the piston down. And the flatter combustion chamber offers less material (124cc to the Hemi’s 167cc of combustion chamber) to further impede heat-energy loss. Additionally, a pent-roof design allows for generous squish areas—flat sections of the chamber roof where the near contact of the piston to the head creates turbulence.
The new Schubeck 904 head has increased this squish even further by adding to the design, a touch of clover. Best described by looking at the picture, the clover shape increases the area for near contact, even further, to help promote turbulence. This provides for better mixture of the charge, which in turn leads to a faster ignition or a “fast burn”, as it is sometimes called. One immediate advantage is the reduction of ignition timing and a more complete burn of the mixture.
The classic pent-roof design shares one commonality with the hemi chamber, namely the centrally placed spark plug.
REDESIGNED FEATURES
The 904 has unique features designed into its valve train For one thing, the four camshafts are hollow, and oil flowing through them lubricates—via a pinhole drilled on the cam lobe’s backside, the main cam bearings and attendant valve train
Each cam rides on a roller bearing rocker that actuates a stainless steel valve. However, the cams are not positioned directly over the valve stem. They are offset back so the camshafts don’t have to be removed to check the valves and the valve springs. That was also the reason inverted, bucket-type tappets were not used.
By their nature, buckets must fit directly over the valve stem and that would make valve and/or spring changing a laborious job. In fact, with the hydraulic valve lifters on the 904, valve lash is not necessary.
The system for turning the camshafts is a rather unique setup as well—a combination gear/belt and pulley/gear system. Its two main advantages are ease of maintenance and reduction in the harmonics that build up with an all-gear system. Also, gone are the traditional copper head gaskets. The 904 uses rubber O-rings, around the oil and water passages, and a special stainless steel ring embedded in the cylinder sleeves that seal the combustion chamber.
STRENGTHENED BLOCK
With the aftermarket “Hemi” there is no block material between the cylinder sleeves, however, the bore center on the 904 have been extended for larger bores to also allow a wall of material between the sleeves. In effect, that ties the top deck and main crankcase together between the cylinders, adding rigidity to the entire block.
Six head studs are spaced around the combustion chamber, closing the unsupported areas present at each end of the Hemi head, where gaskets fail most often. The lower end has been given a beefed up treatment as well. The center main caps are held to the block with 9/16-inch steel studs and with ½-inch main cap bolts angled into the caps at 30 degrees, allowing them to work under tension. The Hemi’s have their main cap side bolts fitted at 90 degrees, which places them under shear loading. The front and rear main caps, also made from steel, are held fast with ½-inch doweled studs.
The 904 cylinder block has a 13.150 tall deck, permitting longer rods that result in less angularity and a better rod length to stroke ratio. Because the cams are in the heads, there is no rod to cam interference with the long stroke.
The 904 also has five “accessory pads” on the front with four additional pads on the valve covers to allow engine accessories to be driven off the four cams if more became necessary.
The new engine has a fully functional cooling system, which Schubeck says was developed specifically for endurance running in offshore powerboat racing. The partition between the cylinders allows for cylinder-fed cross-flow cooling similar to the system employed on Indy Cosworth engines. This eliminates the hot, hotter, hottest syndrome created when automotive type engines are used to develop endurance power. Typically, in this situation, coolant traverses from front to back, picking up heat as it makes it’s way back. Each cylinder’s heat is added and when it reaches the last cylinder, it’s a lot hotter than when it entered from the radiator. In other words, the last cylinder to get cooled is the one more prone to detonate from hot spots. With the 904 cooling system, the coolant first passes into a manifolds cast into the block, coolant is circulated to each cylinder from the manifolds on the outside of the block, up through the exhaust side of the heads and back down from the heads back into the block, leaving the block through the inside manifolds. All this is done with a outside to inside trip for the coolant, thus giving each cylinder the same temperature coolant. This system helps eliminate hot spots that lead to detonation.
The 904 uses a machined billet crankshaft with 3.250-inch main bearings and is supported just ahead of the front main by a roller bearing that is designed into the front accessory case. This increase the strength of the crank, especially if a blower is used atop the engine.
Although the engine is headlined as a marine engine, this does not mean, that if a customer wanted the engine for another challenge, even some form of outlaw drag racing, that it couldn't be dressed for the occasion with a large blower and maybe even a gulp of Nitro.