Supercharged Engine Build - Bad To The Blown
496 Cubic Inches Of ProCharged Power: The Build
From the February, 2009 issue of Chevy High Performance
By Scott Crouse
We live in a world of outrageous street machines capable of making astounding amounts of horsepower. With enough money in hand, horsepower levels are limitless, and a thousand street ponies seem to be becoming the norm. Look around; engines of this caliber are popping up all over cruise nights, car shows, and road trips across the country- -exactly why we've decided to build our own 1,000hp pump-gas big-block. Our goal is to uncover just what it takes to build one of these monsters. We will be right up front and say that unless you are a professional engine builder, this is a time-consuming, expensive project (but one that'll surely impress).
To get things started we contacted SA Engine Design about what it would take to build a street-friendly 1,000-plus-horsepower engine. We filled out a complete SAED preview sheet and presented our requirements: It has to run on pump gasoline (91 octane), be fuel injected, and make at least 1,000 hp at or below 6,500 rpm. Sounds challenging, but we were assured that it wouldn't be impossible. The design called for a 496ci Coast High Performance stroked Rat block, a Comp Cams valvetrain, Dart cylinder heads, a complete ACCEL DFI fuel injection, and an intercooled F2 supercharger from ProCharger. Our recipe for power had arrived, and we dove into the build from the bottom end up.
The engine began its life at Coast High Performance, where a complete 496ci short-block was built with a double-keyway 4.250-inch forged crankshaft, H-beam rods, and 4.311-inch- bore dished pistons. Underlining the crankshaft is a high-performance Milodon oil pump and pick-up covered by a matching 7-quart oil pan. To mate with the crankshaft snout is a double-keyway Fluidampr harmonic balancer responsible for keeping internal engine shakes at a minimum.
Up top we opted for a set of aluminum-casting Dart Pro 1s ported and massaged by High Velocity Heads in Knoxville, Tennessee. While the 335cc intake-runner design may seem small at first, it's anything but. The smaller runner will actually increase low-speed airflow to promote idle quality, while still being more than capable of pounding the grunt on pump gas. Speaking of pump gasoline, the cylinder heads are set up with 119cc combustion chambers to work with 0.053-inch-thick MLS head gaskets. After checking the piston-to-valve clearance we dropped in a set of Schubeck lifters for added insurance. Above and below the mighty lifters is a Comp cam measuring 0.673/0673-inch lift with 256/266-degrees of duration at 0.050 inch, while being ground on a boost-friendly 114-LSA. Above the Schubeck lifters are 3/8-inch-thick, 8.850-inch-long exhaust and 8.050-inch-long intake Hi-Tech Comp Cams pushrods working 1.7:1 Pro Magnum roller-tipped rockers on 7/16-inch studs. All the gaskets are Fel-Pro, while the valve covers are scripted and polished HVH specials. The valve covers come complete but will require a driver-side notch to clear an F2 supercharger. Closing the engine up is a fuel-injected EFI single-plane ACCEL intake manifold that's been topped off with Wilson Manifold's 90mm throttle body and matching side-mount elbow. According to SAED, a 90mm throttle body is more than capable of handling in excess of 1,300 hp, but if there are plans for big boost, a 105mm throttle body and elbow would be the way to go. Something to keep in mind for future reference is that the Wilson elbow and throttle body require substantial hood clearance--so plan on stepping up to a cowl hood if you don't already have one.
With the long-block completely finished an ACCEL DFI Gen VII fuel-injection system was recommended. We ordered a complete kit, which includes the sensors, wires, connectors, computer cables, an electronic control module with instructions, and a Pro-Ram manifold with rails and injectors. In our case the big-block beast would make roughly 10 pounds of boost, so we requested a 2-bar map sensor. All we had left to order was a set of ACCEL fuel injectors, a throttle-position sensor, and an ACCEL adapter harness from the wiring to the distributor. The Gen VII DFI system makes things simple and easy to use for enthusiasts of all fuel-injection skill levels. The system even offers an initial setup page that allows the end users to plug in detailed engine information for a baseline tune. Don't worry about programming; this function will enable you to get the engine fired up, then you can dial in the combination at a later time. In our previous experience with fuel injection, while it isn't a magical horsepower generator, the Gen VII will allow you to tune the idle, increase efficiency for added mileage, and make optimum WOT power whether it's a 300hp street rod or 1,000-plus-horsepower street beast.
While a potent 496ci engine with ported HVH/Dart Pro 1 cylinder heads, a Comp cam, and ACCEL fuel injection is capable of making gobs of power, ProCharger's centrifugal F2 supercharger will create an obscene amount of artificial atmosphere for the power we're looking for. Our complete big-block Chevy kit came with a blow-off valve and most of the necessary brackets, tubing, and clamps. We still need to rig an air-to-air intercooler into the car, but considering our initial test will be completed on an engine dyno, we went to the local metal shop and fabricated a bracket system to hold our intercooler above the engine, so that a dyno fan could blow air through the cooler during each pull.
Mounting the centrifugal supercharger is relatively easy, but there are some areas of caution that engine builders need to look out for. Bolting a blower bracket onto a cylinder head should be done using ProCharger's recommended 7/16-inch accessory bolts. However, most aftermarket heads come with 3/8-inch accessory bolt holes. We ran into this problem with our Dart heads and had to drill and tap them for 7/16-inch bolts prior to engine assembly. Another pitfall most builders encounter is the lack of clearance a blower belt leaves between the timing chain/belt and the blower belt. ProCharger engineers made sure to design a serpentine-acceptable location on their crankshaft pulley for manual-operating water pumps, alternators, and vacuum pumps. To make our lives a little easier on the dyno, a remote water pump would be the only accessory used. While it may all sound a bit tedious and confusing, the actual process of bolting together this engine wasn't that difficult. Most of our problems were solved by obtaining the correct pieces and overcoming pitfalls like notching the valve covers and enlarging the small accessory bolt holes. If an engine design like ours is in your future, expect added build time to chase down parts and eliminate potential gremlins. With a proper design, a lot of patience, and meticulous construction, most high-performance Chevy die-hards can put together their own big-cubic-inch street beast. We've run the horsepower numbers and done the pump-gas math, but nothing will be set in stone until our day on the dyno. Stay tuned and watch out, because this big-block is going to deliver one ferocious punch.
To keep things moving and...
To keep things moving and reliable we had Coast High Performance take care of the bottom-end duties from assembly to camshaft degree. With 496 ci and 8.5:1 dished pistons our blown Rat should pound out some pretty serious dyno numbers.
When boost is an issue, Fel-Pro's...
When boost is an issue, Fel-Pro's multilayered-steel head gaskets are the way to go. While we're only planning to run up to 10 pounds of boost, these babies are capable of handling 20-plus pounds with the correct block-decking procedure.
Cylinder heads make power,...
Cylinder heads make power, which is why we went to Dart Machinery and High Velocity Heads for a set of its heavily massaged 335cc Pro 1 heads, some of the meanest on the market, to provide the grunt when the time comes.
A big-block Chevy valvetrain...
A big-block Chevy valvetrain can be quite complex. The intake and exhaust pushrods are different lengths, plus the large and heavy valves can cause premature valve float. To combat these problems we outfitted our Dart heads with a complete Comp Cams valvetrain and Schubeck lifters.
Since we planned on moving...
Since we planned on moving massive amounts of street-friendly boost, we had HVH port-match the Accel Pro-Ram manifold to the Dart Pro 1 335s.
Wilson Manifolds is well known...
Wilson Manifolds is well known for its championship deliverance of performance and quality. Some customers have made well over 1,300 hp with a 90mm throttle body and matching elbow...so we went with what works.
An ACCEL DFI Gen VII complete...
An ACCEL DFI Gen VII complete fuel-injection system was installed, from injectors to wires. Its fully tunable programming will allow us to control our engine on the dyno as we attempt to make in excess of 1,000 hp below 6,500 rpm.
Compressed air makes boost,...
Compressed air makes boost, and boost makes power. ProCharger delivers one of the meanest centrifugal supercharger kits around, and we're planning to shatter our power goals with one of its F2 air-to-air intercooled big-block systems.