620CI, 1,550HP, Big-Block Chevrolet
QMP Engines, Canoga Park, CA
During an impromptu tour of QMP Engines, owner Brad Lagman made one of those offhanded, "Oh, you might like to see this" statements as he swung open the door of what appeared to be a broom closet between his CNC machining room and the shop's main assembly area. When he hit the lights, he nearly had to pick us up off the floor with a shovel. The 14-71 supercharged big-block Chevy towering over us on the engine dyno was as intimidating as it was good looking-and the last thing we expected to see. Honestly, we shouldn't have been surprised; QMP turns out some really high-end stuff. In addition to the standard Sunnen and Rottler machines you'd expect to see at an engine builder's shop, the company has a full complement of CNC machining equipment. It's entirely possible that QMP could make a complete engine out of a chunk of aluminum.
In spite of its massive stature, this particular big-block is a relatively simple engine. There's nothing too fancy here-just lots of displacement (620 inches) and airflow (17 pounds of boost from a giant supercharger). QMP was just finishing the dyno tuning of this engine, and assembler/dyno operator Mike Consolo gave us the rundown. Though it looks like a Top Fuel powerplant, this engine is actually going in one of its customer's pleasure boats. You can never get to the other side of the lake fast enough.
Though fed by a pair of 1150-cfm Dominators, Consolo told us he maxed out the carbs before the end of the dyno pulls-they couldn't deliver enough fuel to keep up with all the air ingested by the huge supercharger, so he sent them to Book Racing Enterprises, a company specializing in competition carburetors. "I only needed to make one adjustment when I got them back. They were almost perfect," he says. A MagnaFuel Pro Star 500 pump handles fuel delivery. Consolo set the regulator at a rather high 10 psi, but because boats see long durations at or near wide-open conditions, fuel pressure settles in at 8 psi when running. He estimates the engine consumes about 1/4 gallon of gasoline per mile.
An MSD Pro-Billet distributor and HVC-2 coil ensure proper combustion at the right time, every time.
To say the Mooneyham 14-71 supercharger is big is like saying a Top Fuel car is fast. True? Yes, but woefully inadequate. It's a truly awesome spectacle to see it sitting on top of this engine, and it looks so cool all polished up like that. It is perched on an air-to-water intercooler from The Blower Shop, which also supplied the 14mm Kevlar belt and pulley drive system. The pulleys are sized to spin the blower fast enough to deliver 17 pounds of boost. The carburetor adapter is unique because it allows the carbs to be mounted front to back rather than side by side. This makes it easier to mount the throttle linkage and also provides a little better fuel distribution along the supercharger rotors.
Though they look custom, Consolo told us the headers are off-the-shelf, Pro-Stock-style headers from Hooker. They have 23/8- to 21/4-inch stepped primary tubes with 4-inch collectors.
If the engine is relatively basic stuff, the oiling system is anything but. An Aviaid six-stage dry-sump oiling system keeps this thumping engine running like a well-oiled machine (pun intended). Four of the six stages scavenge oil from the pan, another pulls oil out of the lifter valley, and the sixth is positioned on the underside of the intake manifold and sucks up any stray oil floating around above the lifter valley. A handmade aluminum oil pan was needed to accommodate the four scavenging nozzles in the crankcase. The pan basically separates each pair of connecting rods into four discrete compartments, each with its own nozzle. The same guy who made the oil pan also made the sheetmetal valve covers.
F. Vacuum Pump
Though the dry-sump system does offer a side benefit of pulling some crankcase vacuum, Consolo also added this Moroso vacuum pump to eliminate any chance of pressure stacking up underneath the pistons. Even at maximum boost, this system maintains 17 inches of vacuum in the crankcase.
At the foundation of this build is a Dart big-block Chevy. With a 4.560-inch bore and a 4.750-inch Crower crankshaft, you get a displacement of 620.5 ci. We'll call it 620 to keep it simple. With billet Oliver rods and Ross Racing pistons, the engine is set at a 8.25:1 static compression ratio. The Brodix BB5 cylinder heads pack 2.30- and 1.88-inch Manley severe-duty valves in 118cc combustion chambers. Performance Springs Inc. (PSI) supplied the triple valvesprings, and the shaft-mount rocker arm system is from Jesel. Manton tapered pushrods connect to a Comp cam that specs somewhere in the neighborhood of 272/284 degrees duration and 0.800/0.775-inch lift with a 116-degree lobe-separation angle. A Jesel timing belt system connects it back to the crank. Cometic gaskets and ARP fasteners tie everything together.