These days, engines that can generate 800 or more horsepower are nearly as common as prayers on exam day. You hear about them all the time, but the thing that many of the engine builders and magazine scribes forget to mention is just how wound up some of these engines must be to make the number.
The problem with building an engine to hit a number is that it quite often winds up being an absolute dog on the street. The rpm level where it hits peak power is so high you can only reach it on a racetrack, and it’s wound so tight to hit that number that it’s practically a ticking time bomb. A rebuild isn’t a matter of if, but how soon?
We like to keep an eye on the builds at Prestige Motorsports out of Concord, North Carolina, because they generally take the opposite tactic when building engines for their customers. At Prestige, the torque curve is king when it comes to street engines. After all, a big horsepower number is nice to brag about, but it’s torque down low that allows you to boil the tires on the first punch of the throttle.
So when a customer came to Prestige looking for an attention-grabbing engine with eye-watering horsepower to go into a 1966 Chevelle, you’d better believe it also comes with an absolutely vicious torque curve.
The baseline for the build is pure cubic inches. An iron Dart Big M big-block allows for an easy 540 cubic inches thanks to 4.500-inch cylinder bores and a 4.250-inch stroke. Of course, 540-cubic-inch big-blocks are nice, but not exactly unique. To bump the power up from respectable to ridiculous, a gigantic, billet 10-71 BDS blower was sourced and installed on top.
Pushing huge volumes of air and fuel through the aluminum AFR heads, the BDS blower helped this build achieve 910.9 horsepower at 6,700 rpm at just 8.5 psi. And this actually isn’t even peak power—the power levels were still rising when “Senior” at Prestige pulled back on the dyno throttle just shy of seven grand.
Possibly most impressive of all is the fact that from the time we started the pull at 3,500 rpm until 6,700, this big-block ripped off over 700 lb-ft of torque and never dipped below it. The torque peak hit 779 lb-ft at 5,700 rpm. Thanks to the supercharger and all those cubic inches, this isn’t some peaky engine that slogs along until finally making big horsepower at stratospheric rpm levels. This is a beast that spits out tire-shredding torque from idle to redline.
Undoubtedly, the engine could make even more power simply by switching blower drive pulleys to spin the blower faster and make more boost pressure. But this is no race engine. In fact, this package is only beginning to break at sweat at 910 horsepower and 8.5 psi. It runs on pump gas and should be good for many seasons of driving before requiring a rebuild, and it sounds downright evil. Which, in our book, makes it just about perfect for a take-no-prisoners Chevelle. CHP
Prestige Motorsports’ murdered-out big-block should make for a ridiculously fun street engine. It runs happily on pump gas, sounds like a banshee, and makes more than enough torque to spin the tires from idle all the way to its 6,700-rpm redline.
The rotating assembly was chosen based on strength. After all, it must be able to shrug off the tremendous cylinder pressures created by a power-adder. These are Oliver 6.385-inch billet I-beam connecting rods matched with a set of custom slugs from JE Pistons.
The pistons and rods are hung on a Callies Magnum series crankshaft with a 4.250-inch stroke. The main journals are 2.750 inches while the rod journals are 2.200. Callies’ Magnum cranks are shipped from the factory with gun-drilled mains and profiled counterweights, and can handle a ton of power while still being relatively lightweight.
The custom pistons from JE are dished to help keep the compression ratio manageable for boost while also helping to improve flame travel. The block is a Big M from Dart with a 9.800-inch-tall deck. It features priority main oiling and four-bolt steel main caps to withstand big power.
A deep-sump Canton oil pan with a 7-quart capacity uses a removable windage tray and segmented sections to help maintain oil control. Like everything else on the engine, the staff at Prestige spent a lot of time prepping the pan for a smooth coat of semi-gloss black.
The cylinder heads from AFR feature CNC-cut chambers that measure out at 121cc. That keeps the compression ratio at a boost-friendly 8.8:1. The big, 357cc intake ports are also CNC-machined and designed to move the tons of air and fuel pushed through by the blower. One change Prestige did make was to swap out the stainless steel exhaust valves provided by AFR for a set of Ferrea’s “Super Alloy” valves, which should be better able to handle the extreme heat of the supercharged exhaust gasses.
The solid roller valvetrain is based on a camshaft from Comp ground to Prestige’s specs with 0.715/0.717-inch valve lift, 270/280-degree duration at 0.050, and a 114-degree lobe separation angle. The solid roller lifters are from BAM and have a 0.642-inch diameter.
Any time you raise the cylinder pressure with a power-adder you increase the chance of lifting a cylinder head and burning the head gasket. Prestige protected against this by going with Cometic multi-layer steel head gaskets and ARP head studs.
Stock big-blocks use 16 head bolts per bank. The bolt pattern leaves no head bolt directly above cylinders 3, 4, 7, and 8. To improve sealing in those chambers, performance aftermarket heads and blocks add an extra bolt hole over those holes, but it requires a little mechanical gymnastics to get it all together. You actually have to use studs that thread into the deck of the heads then tighten from underneath the head in the block’s valley tray like you see here. To get the nuts properly torqued (70 ft-lb, for this application, just like the studs on top of the block) you will need to use a crow’s foot extension on your torque wrench. Make sure you use the proper correction factors because a crow’s foot attachment can create extra leverage.
This view gives you a good look at the rocker stands on the Jesel Sportsman Series 1.7:1 ratio aluminum rocker arms that helps keep the valve motion nice and stable. The valvesprings are a set of AFR’s 8000 series coils with a 550 lb/in spring rate.
Before it got dropped on the engine, we wanted to show you the business end of the sweet, billet aluminum 10-71 BDS blower. These are the hard-anodized billet steel rotors that will soon be pumping air and fuel into the cylinders.
Like the blower, the intake manifold is all billet aluminum and anodized black. Here, Senior has the gasket in place and is installing a couple of studs to make sure it won’t slide out of position when the blower is set in place.
The burst panel installs on the front of the intake manifold and protects the blower in the event of a backfire.
Here’s the blower in place with a dual-carb setup on top. The break-in is complete and now a pulley change is being made to increase the boost pressure.
The 93-octane fuel is fed through a pair of Quick Fuel Technology 1,050-cfm carbs with mechanical secondaries. A roots-style blower does not require a blow-through carb like a centrifugal blower or turbos, but Quick Fuel does make a few changes to help it work better in a blown setup. For example, there are no power valves in these carbs. On the dyno, we found #94 jets provided the correct air/fuel mixture.
A dual-carb setup can be tricky to get properly tuned, but we found the BDS linkage kit for dual 4150-sized carbs works well. It also includes the hard fuel lines that fitted up easily and make for a sanitary look.
The ignition duties are handled largely by MSD components. An Innovators West damper with an integrated crank trigger marks the position of the rotating assembly, while an MSD boost timing module box controls the timing and sends the spark through an MSD low-profile crank trigger distributor (shown here). We started with 32 degrees BTDC base timing and used the MSD box to pull approximately one degree of timing from the engine for each pound of boost.
BDS provides two reference ports in the intake manifold’s plenum for accurate boost reference. One can be used for a timing controller and the second for a boost reference gauge.
A cogged blower belt doesn’t rely on tension to spin the blower. In fact, too much tension can actually be harmful, as the aluminum manifold and blower case can grow significantly when the engine heats up. This can cause the belt to pull too hard on the blower drive and harm the blower. When the engine is cold the belt should have approximately an inch of slack. A good test is to set the cold belt tension so that it can be spun 90 degrees on the side opposite the tensioner. Check the tension again once the engine is hot to make sure the belt is not too tight.
On the Prestige Motorsports dyno, we pulled the engine from 3,500 to 6,700 rpm and never saw the torque dip below 700 lb-ft. We stopped the pull at 6,700 because the boost had reached 8.5 psi, which was deemed a safe limit, but by then the engine was making 910.9 horsepower. Pretty impressive—especially considering it was burning pump gas and never gave a hint of being close to detonation.
Photography by Jeff Huneycutt