In a world full of 14-71 superchargers, turbochargers the size of 55-gallon fuel-can lids, and multistage nitrous systems, a single four-barrel big-block may not be headline news, especially when it's only 572 ci. Nevertheless, when you can assemble a normally aspirated Rat motor that makes 1,165 hp with only Mother Nature's help in pushing air and fuel into the cylinders, that's worthy of note. Believe it, friends: This single four-barrel Rat makes 2.03 hp/ci. Granted, the engine benefits from some of the best big-block Chevy race-engine builder minds in the country in Reher-Morrison Racing Engines. If that's not enough, you can also find 565-, 665-, or 747ci engines among the all-aluminum R-M packages. Reher-Morrison calls this 572 a bracket engine suitable for Super Gas/Super Comp or Top Dragster-type e.t. racing applications. It is a far cry from stock 454, short-block Super Gas engines, but this is the level of competition that high-speed bracket racing has achieved. Everybody wants to charge the top end with a big mph number.
Anytime we dive into big-cubic-inch engines, the question of average piston speed comes up. The reason we're interested is because the combination of a long stroke and high engine speed yanks pretty hard on the pistons. Some quick research in John Lawlor's Auto Math Handbook (which is sadly out of print now but still available on eBay) reveals the basic formula: stroke (inches) x rpm / 6 = average piston speed in feet per minute (fpm). Plugging in the numbers from R-M's 572, we get 4.250-inch stroke x 7,750 rpm / 6 = 5,489 fpm piston speed. Convert this to feet per second (fps), and the number becomes 91.5. From some of the engineering books we've stumbled through, piston-speed numbers greater than 80 fps are generally termed excessive. What happens with piston-speed numbers this high is that the connecting rod tries to rip the wristpin right out of the piston. Think about this the next time you want to buzz your stroker Rat to 7,000 rpm.
Reher-Morrison also casts its own design of intake manifold for the spread-port, big-block Chevy engines. It incorporates as-cast technology to improve airflow with help from a custom-built Precision Racing Components Dominator carburetor combined with a Reher-Morrison funnel carb spacer and an antireversion plate. The horsepower is the reason these parts are there.
The foundation for this maximum Rat is an all-aluminum, Brodix, 9.800-inch-deck-height, standard-bore-spacing block. Inside is a Callies 4.250-inch, 4340 forged steel crankshaft that's been lightened and fitted with a set of 6.535-inch-long, GRP 5000 Pro series aluminum connecting rods and a set of JE forged pistons built to R-M specs at 4.625 inches in diameter. Total Seal supplied the rings while Trend Tool Steel was responsible for the wristpins (see the Piston Speed sidebar).
The lubrication system consists of a Peterson five-stage dry-sump pump that's hidden behind the Stef's dry-sump tank and vent. It's all connected to a Moroso full-kick-out oil pan.
As with any performance engine, it's the cylinder heads that make all the difference. Reher-Morrison has applied its decades of Pro Stock airflow experience to these Raptor-cast heads with 12-degree valve angles. They use an oval intake-port configuration to flow in excess of 525 cfm with R-M-spec'd, Manley custom titanium 2.450-inch intake valves and 1.850-inch-diameter exhaust valves. Keeping the valves in contact with the cam requires 1.625-inch-diameter Comp Cams triple-wound valvesprings.
Cam And Valvetrain
Another gem hidden deep inside this fat Rat is the Erson 7/4-swap mechanical roller cam. Despite this engine's spectacular horsepower number, the cam is only 285/308 degrees of duration at 0.050-inch tappet lift with 0.825/0.780 inch of valve lift using Isky roller lifters that work against a T&D shaft-mounted rocker system with 1.9:1 and 1.85:1 rockers for the intake and exhaust. All this is driven by a Jesel cogged-belt system.
|POWER CURVE |
|RPM ||TQ ||HP |
|6,200 ||876 ||1,034 |
|6,400 ||867 ||1,057 |
|6,600 ||854 ||1,073 |
|6,800 ||863 ||1,118 |
|7,000 ||860 ||1,147 |
|7,200 ||849 ||1,165 |
|7,400 ||822 ||1,159 |
|7,600 ||800 ||1,158 |
|7,800 ||777 ||1,153 |
|8,000 ||744 ||1,133 |