Holley’s Big Block Giveaway Engine Makes Huge Streetable Power


Holley’s Big Block Giveaway Engine Makes Huge Streetable Power


We are in the midst of a horsepower arms race. Just a decade ago, a 500-horsepower street engine was a big deal. But these days you can just write a check and drive any number of new cars right off the lot with that much power.

But a thousand horsepower? Now we’re getting somewhere!

Hitting four digits on the engine dyno is no easy task. But thanks to advancements in turbo and supercharger technology, many people can build a thousand-horsepower engine -- for a little bit. Usually, these engines are built for publicity so the builder can crow about the achievement on the ol’ internets. But the engines are so highly strung and pushed beyond their practical limits just to hit that number, that they won’t last very long in real-world conditions.

So when Holley and engine builder Prestige Motorsports in Concord, NC, began putting their heads together for their next engine giveaway and wanted to come up with something unique, it didn’t take long for somebody to throw out the possibility of a 1,000-plus horsepower engine.

Of course, nobody wants to give away an engine that’s a ticking time bomb. So priority number one was to make sure whatever engine they built, it is durable and capable of shrugging off abuse. And to make things even tougher, why don’t we make those four digits naturally aspirated in an engine that could be used on the street?

It was also about this same time that Chevrolet had unveiled its 632 cubic inch big block capable of making 1,004 horsepower. There are, however, a couple of drawbacks with Chevrolet’s big-inch big block. One, as we were writing this, production of the Chevrolet engine seems to be pretty limited and even if you wanted to shell out 30 grand for one, they are awfully hard to come by.

The guys at Prestige took that as a bit of a challenge. So the decision was made to build their own version of a 632 cubic inch big block with all aftermarket parts. The Chevrolet engine uses a brand-new, one-off cylinder head casting that’s based on a Pro Stock drag racing design and isn’t available anywhere else. Prestige will be using a set of conventional 18-degree big block heads from AFR that anyone can buy. But to make up for the power loss from not being able to use those Pro Stock heads with equal-length runners is the reason why the compression was bumped up to just over 13 to one and E85 fuel is used. It’s not pump gas, but it’s still viable as a street engine that can also ruin your competitor’s day at the race track.

But by using a Holley Terminator X for the ECU, Prestige found a huge advantage versus the Chevrolet engine. While Chevrolet’s ECU is locked out, all of Holley’s ECUs are not only easy to work with for tuning, but they are also fantastically adaptable. For example, Prestige tested this engine, burning race fuel and E85 right on the dyno with zero hardware changes. The Terminator X ECU handled all the fuel map changes itself.

So check out this behind-the-scenes look at this really cool giveaway build. In the end, Prestige not only hit the thousand-horsepower goal, they vastly exceeded it with 1,106 at a very usable 6,500 rpm. And while that peak horsepower number is certainly impressive, the locomotive levels of torque throughout the rpm range will blow your mind. From the beginning of the pull at 3,900 rpm all the way through 6,500, we never saw less than 780 ft/lbs of torque! Tires will be an endangered species in whatever vehicles this finally goes into!

A street-ready big block that breaks 1,100 horsepower on E85 with readily available parts -- and we never saw less than 780 lb/ft of torque on the dyno? Yes, please!

To make 632 cubic inches you need to give some oversized pistons a lot of stroke. 4.750 inches, in fact, along with 4.600-inch cylinder bores. In order to handle that, engine builder Prestige Motorsports went with a World Products Merlin IV cast iron block. The Merlin blocks come from the factory with machined notches to handle that big 4.750 stroke right out of the box. As you can see, a forged crank from Scat has already been installed.

Those giant slugs are 4.600 in. diameter forgings from Race Tec Pistons. They have a tight compression distance (from the center of the pin bore to the top of the piston) so that H-beam connecting rods from Scat measuring 6.700 inches long can reduce the rod/stroke ratio. Finally, those are coated rod bearings from King fitted in place for the 2.200-inch rod journals.

One of the goals of this build was to maximize power through compression ratio. Thanks to custom flat-top pistons that are just 0.005 of an inch in the hole at TDC and a relatively compact 90cc combustion chamber, the compression ratio will be a healthy 13.2:1. That would make it a detonating time bomb in most street applications, but we’ll be depending on a Holley Terminator X ECU to help handle the timing and fuel maps to keep the engine safe on the street and at the track where it can really shine.

The camshaft is a solid roller from Comp Cams. It is a 4/7 firing order swap, and the duration is 281 degrees for the intakes and 298 for the exhausts at 0.050 tappet lift. It has 112 degrees of lobe separation, and with 1.7:1 ratio rocker arms, gross valve lift will be 0.797 of an inch for the intake valves and 0.787 for the exhausts.

Here's a shot of the business end of the cylinder heads from AFR -- and they are no joke. These heads are fully CNC cut and explicitly designed for big-inch, high-performance big blocks. As mentioned, the combustion chambers are sized at 90 cc’s, while the valve diameters are 2.400 and 1.800 for the intakes and exhausts, respectively. The intake ports are raised a half inch and when sized at 457 cc’s, as these are, can flow as much as 498 cfm at one inch of valve lift.

To improve airflow, the valve angle on the AFR heads is rolled to 18 degrees. T&D has a set of aluminum shaft mount rockers adapted to fit these heads perfectly. They are lashed to 0.008 cold, which should get us close to the hot lash target of 0.014 for the intakes and 0.016 for the exhausts.

The intake manifold is an AFR single plane cast to match the raised runners on the cylinder heads and maximize airflow. It is cast as a Dominator-sized carbureted intake, but the fabricators at Prestige Motorsports have welded in fuel injector bungs to turn this into an EFI engine.

Since we won’t use a carburetor, Prestige has spec’d in one of Holley’s Dominator-flanged four-barrel throttle bodies. This billet aluminum throttle body is designed with everything needed to hook up and operate well with most engine management systems and works extremely well when maximizing power and driveability.

Here’s a better look at how that throttle body manages to flow 2,000 cfm without sacrificing driveability. Big 2.25-inch throttle bores with precise machining are required. To help prevent hang-ups, the throttle shafts are offset so that engine vacuum will assist in closing the throttle plates.

Here, you can see the rest of the fuel delivery setup. Holley fuel rails feed a set of Fuel Injector Clinic injectors sized at 1,200 cc’s. That’s awfully big, but you need a lot of fuel when planning to burn enough E85 to produce well over 1,000 horsepower.

To maximize ignition control and spark at all eight cylinders, Prestige chose to go with Holley’s innovative Big-Wire Coil-Near-Plug kit instead of a conventional distributor and ignition setup with a single coil feeding power to all eight plugs. This is a shelf stock Dual Sync distributor, which is used to track the position of both the crankshaft and the cam for the ECU, but since we don’t need plug wires the distributor cap has been swapped out for one of Holley’s billet blank distributor caps to clean up the look.

For dyno testing, Prestige just hooked the eight Holley smart coils to a bracket fabricated and mounted in a convenient spot away from harm. Once the engine is in the car, the smart coils can be mounted on the firewall or practically wherever the owner wants.

We mentioned earlier that this engine has a really high 13.2:1 compression ratio, which means no matter what fuel you are burning, you will need exact engine controls to keep from getting into detonation when the engine is under load. Interestingly, everything was handled through an off-the-shelf Holley Terminator X ECU. Prestige Motorsports is one of the few engine builders not on the NASCAR Cup or other similar professional racing series level that has invested in the capability to monitor individual O2 levels in all eight cylinders in real-time. Here, they make individual cylinder timing adjustments through the Terminator X and included software. Obviously, this isn’t something that most engine builders or car owners will get into, but it’s impressive that advanced capability is built right into every Terminator X unit.

On the dyno, we ran the big 632 both on race gas and E85 fuel -- and the Terminator X handled both. You will notice that we did add an alternator, which was just to provide a bit more juice to power the eight O2 sensors, and a one-inch spacer underneath the throttle body. With race gas, we saw a little over a thousand horsepower, but things really got fun when we switched over to E85. Power jumped way up to 1,106 at just 6,500 rpm and we never saw less than 780 ft/lbs or torque throughout the pull!


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