A Look At Geoff Turk’s Seven-Second Stock Eliminator Engine Effort

Stock Eliminator is a complicated—and sometimes hard-to-understand—class for anyone but those deeply entrenched in the NHRA class-racing world, with engines that are best described as technological marvels. Unfortunately, those cars generally remain out of the spotlight of the general public. To try to remedy that, NHRA teamed up with the Big Three to get the Factory Stock Showdown class rolling, which showcases the lineup of late-model factory hot rods, and makes Stock Class racing more palatable to those who might otherwise overlook the awesome class.

One of the features of the Factory Stock Showdown, from our perspective here at EngineLabs, is that these late-model cars are using late-model powerplants. With the popularity and backing the class and its participants are enjoying, 2017 was a race to the sevens, and out of the middle of the pack, emerged Geoff Turk and his “Blackbird” supercharged Drag Pak Challenger, powered by a Gen III Hemi engine.

After setting the quickest run recorded in NHRA Stock Eliminator at the end of last season with an 8.02, it was only a matter of time before he broke into the seven-second zone ahead of all of the other competitors in the class. It actually wasn’t that long, as Turk smashed the barrier at the first NMCA race of the season (NMCA has a class which mirrors the NHRA class rules), carding a 7.996 in qualifying, and posting a 7.994 in the final round at the following race in Atlanta, Georgia.

Geoff Turk with his crew chief and number one supporter, his wife, Sandy.

Understanding The Man

While a deep dive into the engine and the Gen III Hemi platform is important, it’s also important to understand how a self-described “small-time” Stock racer put himself—and the Gen III Hemi engine—into the history books, after seemingly coming out of nowhere.

“I grew up drag racing, and started when I was 13 years old,” says Turk. “When the Stock Eliminator guys came to the track, we thought they were the snobby rich people that had stuff that was way nicer than our stuff. While we made fun of them, we respected them.”

The new aluminum engine’s shortblock consists of some serious hardware, and specs out to an actual displacement of 363 cubic-inches, thanks to the 4.125-inch bore and the 3.400-inch stroke.

After almost two decades of bracket racing, Turk entered the world of class racing in a 1973 Plymouth Roadrunner. A string of Stock-class Mopars culminated in a 1968 Hemi Barracuda Super Stock car.

“That was one of the most ornery, expensive, difficult, tear-stuff-up cars in the world,” Turk says “After wearing out myself and my bank account running that car, I decided to step back and run a 1968 Barracuda with a 5.7L Gen III Hemi in it. That was fun but boring.”

Looking to get the thrill back, and being interested in the late-model cars, Turk almost strayed from his beloved Mopar for a Mustang Cobra Jet before coming to his senses. The Supercharged Drag Pak Challenger was announced and Turk was first in line.

“I saw the Factory Shootout stuff happening, but I knew that was going to draw in a lot of resources and a lot of talent, and a lot of money,” says Turk. “I didn’t want to get back into that and spend money like that again. I was just going to camp out in Super Stock and have fun.”

However, at the 2016 U.S. Nationals, a chance meeting with Mopar’s Dale Aldo revealed that Turk was running quicker than the Mopar factory effort in the Factory Stock Shootout, while being almost 100 pounds heavier. That started the ball rolling for Turk’s path into the history books, in the middle of 2016.

“[Aldo] asked me if I’d think about running the Factory Shootout with the car. I told him, if he was serious, I’d call Tony Bischoff right then and start an engine.”

Dubbed “Blackbird” after the SR-71 reconnaissance aircraft that is the fastest operational aircraft ever, Turk’s MR2 Performance-built Challenger Drag Pak is the quickest Stock Eliminator car in the world.

Evolution of the Engine Program

When Turk came out of the gate at the beginning of 2017, he was running an iron block Gen III Hemi combination built by BES Racing that was considered “old technology” by Stock-class standards, as the new aluminum block had just been approved for competition.

“I qualified number-six in a 30-car field, with an 8.20. Everyone thought it was a fluke, and that I got lucky. At the next race, which was Charlotte, I qualified fifth or sixth there,” says Turk.

That performance impressed the Mopar factory folks, a large “M” appeared on the car, and the latest and greatest parts and factory support boosted Turk’s effort. After running an impressive 8.20 in the heat of the summer with the iron-block engine combination, everyone involved decided it was time to apply everything they’d learned so far to the latest and greatest aluminum engine combination.

The Combination

Turk has relied on Tony Bischoff and his team at BES for his Gen III Hemi builds from the get-go, and the new aluminum- combination was no different. There is a lot of advanced engine building that goes into a state of the art class engine like this, with a lot of closely guarded secrets to make the engine perform as well as it does, within the strict confines of the rulebook.

The 363 cubic-inch Gen III Hemi engine is pressurized by the class-standard 2.9-liter Whipple twin-screw supercharger and is said to make 1,250 horsepower and 900 pound-feet of torque, while spinning north of 8,500 rpm.

This Mopar Drag Pak supercharged 354 engine starts out with the Mopar aluminum block bored to 4.125-inch, with a 3.400-inch stroke Winberg crank added for an actual displacement of 363 cubic-inches. Carillo rods connect the custom Diamond Racing pistons—which, word has, bump the compression to numbers normally thought to be insane to run with boost—to the crank, while Total Seal rings are utilized to keep the compression in the cylinders. Clevite bearings are used in the main and rod journals, and a Melling oil pump keeps the engine’s lifeblood circulating. A custom Moroso oil pan with all the bells and whistles helps control the oil, and a Manley timing set keeps the engine in time during its max-effort jaunts down the quarter-mile.

“The JR1 Racing Oil has consistently been a great product with real advantages,” says Turk of his racing lubricant.

The aluminum Mopar block at the core of Turk’s record-setting engine features 4.125-inch bores. Previously, Turk ran an iron-block combination that left everyone surprised at his performances.

Up top are a set of Mopar’s high-performance cylinder heads, which Mopar has extensively refined specifically for class racing. A custom BES-specified Comp Cams camshaft actuates Jesel lifters and Trend pushrods. T&D rockers convert the cam motion into valve motion, and the Xceldyne valves are controlled by PAC valve springs. “Most of these guys will make good power to about 8,200 rpm and then will cross the line about at 8,600-8,700,” Bischoff says of this caliber of engine.

A class-spec 2.9-liter Whipple twin-screw supercharger provides the compressed atmosphere, while a Holley EFI system controls the fuel and spark portions of the equation.

“Everybody has to run the same blower. That’s part of what makes the class so fair,” says Bischoff. “Chrysler has a great foundation to start with, so naturally it’s going to make good power. Then we just have to figure out how to tune it and keep them together. I’d like to take credit for it, but I think we get more credit than we deserve, however I’ll take it.”

The Gen III Hemi’s cylinder heads are Mopar pieces with an OEM part number, per the Stock Eliminator class rules. But make no mistake, these heads come from Mopar ready to rock and roll in this application.

The combination is powered by gasoline, as defined by the NHRA rulebook, and makes 1,250 horsepower and 900 pound-feet of torque on the engine dyno.

“They make about the power I expected them to make,” says Bischoff. “I’ll be honest with you, the cars run faster than what the horsepower says they should. That kind of surprises me, and I’m not sure why that is. They are almost 3,600 pounds, and now going 7.90s, that says 1,400 horsepower, but I have no idea where that comes from, because this makes 1,250.”

Building a competitive—let alone record-setting—class engine is no small feat, but this is by no means Bischoff’s first rodeo with the Gen III Hemi.

“We do a ton of Gen III Hemis for street cars for HHP, but I’ve found they are a very durable motor and they make great power. It’s an awesome platform for a factory motor,” Bischoff says.

However that doesn’t mean there weren’t challenges faced along the way.

“Being as we build a lot of those motors, and really, we build a lot of any kind of motors, we have struggled through some problems that all the brands have suffered,” says Bischoff of the Stock-class engines. “There are some things than can burn a motor up really easily if you aren’t on top of it. After all, these are boosted engines on gasoline. Your tuning window can get really small, and it’s hell on pistons, I can tell you that!”

Tony Bischoff feels the hemispherical combustion chamber and dual spark plugs from the factory are solid advantages for the Gen III Hemi in this supercharged application.

Turk’s opinion on the engines longevity is that of a heads-up racer.

“There has been some rumbling about the need to change the rules to make the engines more robust, and I think that’s a bunch of hooey, to be blunt,” he says. “If you give us rules, we’re going to push to the edge of the rules. If they told us we could have O-ringed blocks, we’d start finding ways to blow up O-ring blocks.”

Another challenge experienced along the way, was the non-traditional intake manifold design of the twin-screw supercharger.

“You’ve got to cam [a Whipple engine] correctly. I mean, any motor has to be cammed correctly, but because of the Whipple design, and this is the same for all three [engine] designs, the blower is right on top of the engine. That is where it originally threw me for a loop, for lack of a better term,” Bischoff says. “There is no real intake runner on them anymore. There’s basically just a cylinder head and the plenum with no big, long runners. That changes the cam design a lot. You’ve got this little short manifold, with the blower sitting right on top of it. The motors ended up wanting a lot different cam than I thought they’d want.”

The result of Turk’s hard work. Turk is quick to give the credit to those that have helped him, like BES Racing and Coan Engineering. That 170 mile-per-hour trap speed has even Tony Bischoff wondering where it’s coming from.

All of the brands in the class run really close to one another, ET-wise, which is a rulemaker’s dream, but of the three manufacturers, Mopar is definitely the least represented within the field itself, which is surprising.

“Each platform has its advantages,” says Bischoff of the Hemi, LS/LT, and Coyote platforms. “One thing for sure, I think the dual plug design is an advantage. The Hemi chamber design actually lends itself towards boost out of the gate. Those are the two big things, really.”

The Future

In addition to having his name forever linked to the first seven-second Stock Eliminator pass, Turk won a special $10,000 bounty put on by the NMCA and Holley.

“This would be the season of my life, even if I parked it after making that pass,” Turk says. “Beyond the money, is the fact that I go down in history as the first seven second Stock Eliminator car.”

With his name in the record books, Turk is not about to kick his feet up and turn on cruise control for the rest of the season.

“The only way to keep up is to be constantly working. In this heads-up racing you can never rest,” says Turk. “We push the limit, and then maybe break something, or push the limit and something doesn’t work, but we are always pushing. Tony Bischoff is a remarkable engine builder along with his team, and Jason Coan at Coan Engineering really help me with that.”

However, it’s not just the desire to go faster that is motivating Turk, but also the desire for a championship.

“My wife’s health will be the priority, however, and will define what we can and can’t do,” says Turk. “God-willing, the schedules will not only line up to let me be at the races, but allow her to come with me. I want to do the best I can to represent all the hard work of the people who really make all this happen for me. I feel like wanting to win a championship is a little greedy, but I want to show that we can keep going rounds and running sevens,” Turk says.

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About the author

Greg Acosta

Greg has spent fifteen 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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