Fork in the Road

We explore two paths to big horsepower: One starts with less and adds more, the other starts with more and adds less. Both involve LMR-tuned C6 Corvettes.

June 15, 2010

Also from Issue 59

  • C6 show car
  • State of the collector-car market
  • Interview: Jim Campbell
  • 1972 LT1 coupe
  • Pratt & Miller LS7/LS9 engine
  • History: 1960 24 Hours of Le Mans
  • Racing: Laguna Seca ALMS
  • How To: C2/3 frame repair
  • 1965 small-block coupe
  • 1972 LT1 coupe
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It’s the horsepower junkie’s dilemma: Should I buy a less expensive car and drop a serious stack of money making it faster, or opt for a pricier, more powerful model and invest less in performance mods? We recently had the opportunity to explore these two paths, Corvette-style, thanks to the crew at Late Model Racecraft (LMR) in Houston, Texas. The dueling pair of LMR-tuned cars were a 2009 ZR1 packing an upgraded, 810-horsepower LS9 engine and a 2008 C6 coupe with a monster 1,200-bhp twin-turbo 440-cubic-inch V8. Both offer outrageous levels of performance, but at what price‚ both in terms of actual dollars spent and livability on the road? Gentlemen, choose your weapons!

Base-model Buildup

A standard LS3 coupe is a serious road machine. Even in dead-stock 430-bhp form, it runs the quarter in the mid-12s and tops out at around 190 mph. Considering its MSRP is just under $49,000, the base Corvette offers a ton of performance for the money, and begs the question: “Do you really need any more performance than that?” Perhaps not, but if you’re reading this magazine you definitely want more!

R.C. Cox certainly did. He picked up his automatic-equipped ‚Äô08 C6 new two years ago. The odometer read less than 1,000 miles when the car made its first visit to LMR. In went a Procharger D1 supercharger, a pair of headers, a cam and a new torque converter for the tranny. The result on the LMR chassis dyno was 650 rear-wheel horsepower (rwhp), which was enough to eclipse the output of just about every production car on the road‚ but not enough to satisfy Cox. The car was soon back at LMR.

On its second visit, the Corvette was treated to a whole new engine. Out went the supercharged 376-cubic-inch LS3 and in went a turbocharged 440-cubic-inch behemoth. Not content to merely bolt in an off-the-shelf motor, LMR started with a World Products Warhawk six-bolt block, into which it mounted a Callies 4.100 Dragonslayer crank. Callies H-beam rods swing custom Wiseco 9:1 slugs fed by a custom LMR cam grind. The All Pro LS7 Hurricane heads feature Jesel shaft-mount 1.8-ratio rockers and 2.200-inch hollow-stem stainless-steel intake valves and 1.600-inch Inconel exhaust valves.

On the intake side, twin APS GT-35R turbos were bolted on using an APS kit that allowed them to be mounted low, on the bottom side of the engine. A large air-to-air intercooler was also added, along with a Weldon race-spec fuel pump, 86-pound/hour fuel injectors and a custom-fabricated surge tank.

Spent gases are emptied by a pair of APS exhaust manifolds. These feed into a custom 3-inch-diameter oval-tube stainless-steel exhaust system fabbed by LMR partner Josh Ledford. Though B&B Fusion mufflers quiet things down a bit, DMH low-profile electric cutouts allow bystanders to hear the full banshee scream by bypassing the mufflers, adding a few ponies in the bargain.

What is the result of all this tuning? A whopping 1151 rwhp, and that’s not counting a 200-horse shot of juice from a Nitrous Outlet nitrous-oxide system.

Getting all that power to the pavement required a lot of drivetrain upgrades. Circle D Transmissions of Houston installed an RPM Transmissions 4L80 automatic coupled with a 3-disc lockup converter. The Driveshaft Shop built a custom driveshaft that can withstand 1,200 horsepower this after the previous shaft came apart on the dyno at 1,000 bhp. This outfit also supplied custom heavy-duty halfshafts. To help cool the monster motor, a custom Ron Davis four-core radiator was installed, along with twin SPAL cooling fans.

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