737CI, 2,200HP, AES Big-Block Chevy
Jim Robbins, Elk Grove, IL
It takes serious horsepower to compete in the Super Street and Outlaw 10.5 classes these days. We're talking more than 2,000 hp. While most of these racers rely on a pair of hair dryers, there are a few still doing it with nitrous, including Jim Robbins, who uses a massive 737ci Rat with a load of spray combined with EFI. The car is a full-tube-chassis '68 Camaro running 6.83 at 206 mph on a 10.5W tire. Robbins' Camaro is also one of the few running a Lenco five-speed. We caught up with him at the NMCA finals in Memphis, where he qualified Eighth. Unfortunately, this paired him against perennial powerhouse Spiro Pappas' twin-turbocharged Camaro and Robbins' weekend was over a little too soon. We were interested in an insider's look at this massive nitrous big-block built by Automotive Engine Specialties' Anthony Schroeder out of his Elk Grove Village, Illinois, shop. If this looks like fun, Schroeder says he can build a clone for a mere $85,000. How many do you want?
1. Idle Speed
Anthony had difficulty chasing idle speed with the multiple throttle bodies since every time he changed the throttle opening, it also affected the throttle position sensor (TPS). "It got to be a pain," Anthony says, "so I came up with this idea." Each of these brass restrictors is a blank Holley air bleed. Anthony drilled 10 holes in the manifold and merely adds or removes individual bleeds to set the idle speed. Removing one bleed is worth about 100 rpm. How's that for innovative?
2. Eight Barrels Of Airflow
After you look at all the plumbing involved with monster twin turbos, this engine is elegant in its simplicity. But that takes nothing away from its 2,000-plus-horsepower potential. Starting with those Applied Nitrous throttle bodies, each of the eight barrels measures 21/4 inches in diameter, feeding a Wilson custom sheetmetal intake designed for the tall-deck engine. Nitrous Pro-Flow also handles all four stages of nitrous. The stages flow like this: Stage 1 is 250, stage 2 is 300, stage 3 is 250, followed by stage 4's 100 hit. That adds up to 900 hp-give or take a hundred.
3. Clutch
Schroeder says the team is still trying to get a handle on the clutch to help get the car down the track. The Racecraft chassis does its part as does the Ram twin-10-inch clutch, but that still makes for a busy pass. Robbins is into Fifth gear by the time he reaches the eighth-mile, and the car's best pass in the 660 is a 4.49 at 162 mph. Just let that sink in for a moment.
4. Electronics
With no carburetors, Schroeder takes command of the fuel and spark curve with help from a FAST electronic package that offers sequential control over individual cylinders. He says the No. 6 hole tends to run lean, which means he retards that cylinder a couple of degrees and adds roughly 8 percent additional fuel. The injectors are also FAST and big enough at 160 lb/hr to help feed this behemoth.
5. Heads Up
Carl Foltz is the man behind the heads for this ground-pounder, which sports a set of CFE 18-degree Pro Mod heads that feature 2.48/1.90-inch titanium valves. Schroeder says since they only spin the engine to 8,400, they don't have to do nearly as much valvetrain maintenance as they used to with the older 454-based engine, which they had to spin up over 10,000 rpm. The PSI valvesprings are rated at 430 pounds of load closed and around 1,400 pounds open.
6. Feedback
The conservative tune-up means they rarely burn up parts, but part of the reason is the feedback from the eight RacePak wide-band oxygen sensors, one located in each of the eight 21/2-inch primary header tubes. Even with the electronic feedback, Schroeder still relies as much on what the spark plugs look like after every run.
7. Short-BlockThe foundation begins as a billet, 5.0-inch-bore-spacing, Dart, tall-deck, aluminum block that spans a monstrous 11.100 inches from the crank centerline to the deck. Bryant supplied the equally lengthy 5.200-inch stroker crank that spins a set of 7.120-inch-long GRP aluminum rods with 4.75-inch-diameter CP pistons that squeeze the compression up to 14.5:1. Schroeder says they routinely spin this engine up to 8,400 rpm. We did the math-the pistons have to cover that 5.2-inch stroke distance twice, repeating the process 140 times per second at 8,400 rpm. That means the pistons are moving 121 feet every second at that speed in addition to stopping and starting at both ends. Schroeder wouldn't say much about the cam other than it's a Bullet custom mechanical roller that will push the intakes over 1.10 inches of valve opening.