Making More Than 1,200 Horsepower On The Dyno With Our Giveaway HEMI

If you haven’t been living under a rock, you are probably familiar with our EngineLabs Engine Giveaway, presented by Summit Racing. We have shown you the process of our 1,200-horsepower Gen-III HEMI Giveaway engine coming to life in several previous articles. First, we showed you the short-block assembly, followed by the long-block and Whipple supercharger going onto the engine, both of which occurred live on the PRI Show floor.

While it’s an impressive piece of equipment, technically, it’s Schrodinger’s 1,200-horsepower Gen-III HEMI, since it hasn’t turned the crank in anger yet. (Kudos to you, if you get that joke.) The next step in the process is for us to rejoin the engine at Late Model Engines in Houston, Texas, strap it to the engine dyno, and let ‘er eat.

In case you aren’t familiar with the Giveaway Engine, we have built a Gen-III HEMI with some of the best parts the aftermarket has to offer, and the pièce de résistance is the brand-new-to-the-market Whipple Gen-6 3.8-liter twin-screw supercharger. The modern supercharger is capable of making far more than the paltry (by comparison to its capabilities) 1,200 horsepower we’re asking of it. You can catch up on the short-block build here, and the long-block, here.

Getting The Engine Ready

The first thing we needed to do, once the engine was back at LME after being assembled at the PRI Show, was to swap the crank pulley. We originally opted for an ATI Super Damper in a 10-percent overdrive configuration. However, Dustin Whipple quickly informed us at the show that we’d make way more than we wanted to with that size pulley, and since we were already more or less maxxed out on blower pulley size, we should swap to an OE-sized pulley.

ATI was gracious enough to send over the regular-sized Super Damper, and we swapped it on. Also, since we wanted to do more than just make 1,200 horsepower, we wanted to do a little testing. We wanted to see how much we could make with OEM Hellcat exhaust manifolds, and see how much power we picked up by simply swapping them out for a set of Kooks headers.

In the front, you can see the standard OE-diameter ATI Super Damper, with the 10-percent overdrive version in the back. On Dustin Whipple’s suggestion, we started with the smaller crank pulley.

The headers in question were a pair of Kooks’ stainless steel long-tubes, with massive 2.0-inch diameter primary tubes feeding into a 3.0-inch collector that expands to 3.5 inches. Common sense holds that on a high-power supercharged application, you want to get the huge volume of spent gasses out of the engine as quickly and efficiently as possible. No small task to ask of headers in a 1,200-horsepower application, but the Kooks long-tubes are designed to do exactly that.

Another interesting aspect of this dyno test is that we are going to be trying to make the power on 93-octane pump gas. Now, we’re not totally insane, so it’s pump gas with a calibrated splash of Boostane’s “Professional” additive. Designed to turn pump gas into an actual performance fuel, it’s so much more than just an octane booster. Spoiler alert, we have used the product before, and we trust it to do exactly what it says. In fact, it’s included in the Whipple Superchargers instruction manual as a recommended product.

Making power through the stock manifolds is no easy task. Thankfully, we have a set of Kooks tubular headers for it as well.

Once we had the Giveaway HEMI bolted up to the dyno cart and mated to the dyno, we fitted the OEM Hellcat exhaust manifolds to the engine — a unique design in and of itself, as they certainly aren’t just a standard OEM exhaust manifold. We then did a little math, to blend the Boostane Professional with the pump gas in the dyno’s fuel cell.

While the small dyno fuel system could have made for some confusing calculations, Boostane actually has a calculator online that factors in base octane, target octane, and fuel system volume, and spits out an exact measurement, removing all the guesswork. For our use case, it told us to add 9.52 ounces of the professional to the 3.5-gallon fuel system on the dyno, to get a nominal rating of 103.

The BOOSTane online calculator showed that to turn our 3.5 gallons of 93 octane into 103 octane fuel, we only needed to add 9.52 ounces of BOOSTane Professional. We rounded up to 10 ounces, for ease of measuring, and added it into the fuel cell.

Round 1, Fight!

The first step on any fresh engine build is to break the engine in. To do that we used AMSOIL’s break-in oil, and ran the SuperFlow dyno’s built-in break-in programming. It consists of short sweeps of varying loads, in order to get the piston rings seated into the cylinder walls of the Gen-III HEMI. The key to any break-in, whether on an engine dyno or actually in a vehicle, is that load. You need combustion pressure to act on the rings to get them to properly bed into the cylinder walls.

For the break-in (and power pulls) we ran AMSOIL’s straight 30-weight break in oil. It helps the rings seat quickly due to a lack of friction modifiers, but has high film-strength and a good amount of ZDDP to minimize the amount of wear experienced by components.

Once the engine was broken in, we were already over the 1,000 horsepower mark, without making any legitimate power pulls. On the dyno controls was our trusty partner Vinnie Monighetti, and he had an eagle eye on all of the data logs to make sure all of our fuel maps were good, before making any full-boogie pulls. Thanks to Fuel Injector Clinic’s easily available injector data, the 1,440 cc/min injectors we used on the build were dialed in without any fuss and we started creeping up on the tuneup.

The first 100-percent (WOT) pull we made showed 1,167 horsepower and 1,027 lb-ft of torque. After reading the plugs and adding a small amount of timing, we made another pull, yielding an oh-so-close 1,199.0 horsepower. Vinnie added another half-degree of timing only for us to lose a few horsepower, indicating to us we were “there” on the tuneup. So with that, we called it done on the factory exhaust manifolds. Our goals were almost met, and we still had a set of tubular headers to fit to the engine.

Here you can see the difference between the OE Hellcat manifold (left) and the Kooks 2-inch-primary tubular headers. The Kooks long-tubes are designed specifically for big-boost HEMI applications.

Round Two — Let’s Go!

The next morning, with the engine cool enough to touch, we set out to swapping-out the HEMI’s Hellcat manifolds, and installing the Kooks stainless steel headers, with their massive 2.0-inch primary tubes. It almost seemed too easy, as usually when you are fitting headers designed for a vehicle onto the dyno you expect at least a few hiccups, but no issues arose with our HEMI.

The extra power provided by the headers proved to be similarly easy to come by. After making a few pulls with the headers, and getting one fat dyno line, we pulled a couple of spark plugs to see if there was any more to throw at it in the tuneup (we were getting greedy with how easily we just made more power with the Kooks headers), but the plugs told us, the engine was happy where it was.

A two-inch primary might not sound that big, but in-person, it is quite large — especially on a small-block engine. These headers were worth 68 horsepower in the apples-to-apples comparison. Spinning the engine higher would see even bigger gains, since the graph was still going up at 6,800 rpm.

The dyno graph was incredibly enlightening as to what was happening. Sure, the extra 68 peak horsepower from just a header swap, with no tuning changes was incredible, but we like to dive into the details. Looking at the horsepower and torque graphs, at 4,700 rpm the traces were identical, but beyond that the traces diverged more and more as the RPM increased.

At 6,500 rpm, the real divergence occurred, as the Hellcat manifolds were out of breath and nosing over hard, whereas the Kooks headers were just hitting their stride, with the graph still climbing. In order to provide a true apples-to-apples comparison, we stopped the Kooks pull at the same 6,800 rpm as the Hellcat manifolds. But, had we let it go, even to just 7,000 rpm, the numbers would have been even more impressive.

Giveaway HEMI dyno graph

Here you can see the final results. The red trace is through the OEM exhaust manifolds and the black is with the Kooks headers. While the peaks show a solid improvement (1,199.0 horsepower vs 1,267.3 horsepower) the area under the curve shows the real gains, especially above 6,500 rpm.

Our final numbers for the Giveaway HEMI Engine are 1,267.3 horsepower at 6,800 rpm and 1,069.7 lb-ft of torque at 5,300 rpm. All that at 17 pounds of boost from the Whipple Gen-6 3.8-liter supercharger, on 93-octane pump gas, with BOOSTane Professional additive. Whoever wins this is getting one potent engine combination, especially when you consider that you won’t be able to turn the blower down much. There might be enough room on the supercharger to add another 0.125 inch to the blower pulley diameter, but it’ll be tight.

The Fuel Injector Clinic 1,440 cc/min fuel injectors gave us more than enough fuel to make 1,267 horsepower on pump gas.

Assuming you are reading this before April 2, 2024, there is still time to get entered, so head over to and enter to win this awesome engine. And, here’s an extra entry code: FIREDOME (if you are just getting entered, go check back in the previous article on our 1,200-horsepower Gen-III HEMI Giveaway Engine, as they contain other codes for additional entries — there are five codes, total).

The 2023 EngineLabs’ Engine Giveaway is presented by Summit Racing and made possible thanks to partnerships with Late Model Engines, AMSOIL, Automotive Racing Products, ATI Performance Products, BendPak, BOOSTane, Brisk Racing, Callies Performance Products, Cam Motion, Cometic Gaskets, Diamond Pistons, Fuel Injector Clinic, Jesel Valvetrain, Johnson Lifters, King Engine Bearings, Kooks Custom Headers, Melling, Milodon, Performance Distributors, Powermaster Performance, Thitek, Total Seal, and Whipple Superchargers.

EngineLabs Giveaway HEMI

Here’s the Giveaway HEMI in all of its glory. The winner will receive an incredibly potent powerplant, so make sure you’re entered for the chance to have this engine be yours.

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Greg Acosta

Greg has spent nineteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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