When Austin Ennis first bought his LS1-powered 2004 Pontiac GTO back in 2009, he had the same ambitions that many of us have. He wanted something he could add a few go-fast parts to, have a lot of fun driving and occasionally take to the drag strip. But, like many of us, after that first bite of the speed bug, there was no turning back.

After installing a few speed parts, Ennis went down what he refers to as “the wrong path.” In the quest to wring as much horsepower as possible from the Goat’s factory LS1, he selected the largest cam he could stuff into the mill without having to fly-cut the pistons; the Texas Speed & Performance Magic Stick 4 — more popularly referred to as the MS4.

After adding a 3,600 rpm stall converter to the mix, Ennis was content with the newly found power for a couple of years. But eventually, as it always does, the need for more power arose, so the search for a set of heads began.

In order to take advantage of the newly found lift and duration, Ennis opted for a set of Trick Flow GenX 220 Fast As Cast heads with TSP valve springs. This saw power output rise to 434 horsepower and 380 lb-ft of torque at the wheels—enough to propel the GTO into the 12’s. 

“The best pass on that setup was 12.9 on stock suspension and a 285/40/R18 Nitto NT05R tire,” Ennis said. “That build was one of my biggest learning opportunities.”

And while there is no doubt that the combination could have gone faster, especially considering the max-effort parts that comprised the naturally-aspirated LS1, eventually one of the springs let go and sent a valve into the great beyond after coming face to face with a piston.

Armed with the experience acquired from building the GTO over the previous five years, Ennis set out to build an unassuming street car that just might surprise anything that it lined up against.

“I’m not a flashy guy, I don’t want things to look over the top,” Ennis said. “I try to keep the cars clean.”

Phase two of the build began at the SDPC Race Shop where the 416 was built for heavy doses of laughing gas and was one of the first builds to ever roll out of the new facility’s doors. The mill features a forged 4340 steel Callies Comp Star crankshaft spinning Callies Comp Star h-beam connecting rods. Dished forged Wiseco pistons, wrapped in a custom set of Wiseco pistons rings specifically designed to handle nitrous, ensure that every combustion event is transferred efficiently to the connecting rods. 

An off-the-shelf Comp Cams camshaft sends lift to a set of stock LS3 rockers that have been upgraded with a Comp Cams trunnion kit for more precise valve control. Stock LS3 heads have been treated to CNC porting for better flow and produce a relatively conservative 11:1 compression ratio. The heads are fed by a stock LS3 intake.

Spent exhaust gases are sped away by 1 3/4-inch Dynatech headers that feed into a custom-built mandrel-bent dual exhaust with X pipe and dual electric cutouts. The growl the 416 produces is tamed by twin Magnaflow mufflers.

Race Proven Motorsports, out of New Castle, Delaware, handled all tuning duties as well as a substantial portion of the work involved with getting Ennis’s GTO to the point it is today.

The tricked out LS3 is backed by a Level VI 4L65E from RPM transmission and is fed by a Circle D 3,600 rpm stall torque converter. All that twist is then transferred to a carbon fiber drive shaft and sent out back to a Gforce Engineering 9-inch rear end. The GTO retains its independent rear suspension and uses upgraded Gforce Engineering Outlaw Anti-Wheel Hop Level 5 axels (rated up to 1,500 horsepower) to send power out to the wheels.

Custom Weld wheels shod in a 28-inch tall Mickey Thompson ET Pro 275/60 attempt to plant all that power while skinnies up front are basically just along for the ride. Ennis’s  front wheels were actually the first of their kind, specifically built for the GTO’s unique backspacing and bolt pattern needs. The rears were pieces that Weld had not manufactured in years.

“We had a hard time finding wheel that would work that didn’t end up sticking out like a tractor,” Ennis said. “Weld hooked us up and we received the first set of these wheels.”

Ennis also intends to give the Goat a 200 shot of “insurance” as well.

“So far, on the shake down runs, it’s gone as fast as 10.91,” Ennis said. “We think it will go mid-10s all motor and possibly go mid-9s on the spray.”

Just looking at the engine—or even the exterior—there are very few cues that this Goat is packing that much punch, and that’s the way that he prefers it.

“We wanted to keep it looking somewhat stock, not like a race car,” Ennis said.

But whether or not it looks like a race car, at heart, it definitely is one. And everyone knows it’s what’s on the inside that counts anyway.