So you want to go fast? All the ads will tell you it's as easy as buying some manufacturer's product and bolting it on. But, as you might imagine, there's more to the story. Recently, we visited with Tony DeMambro in Falmouth, Massachusetts, to get the real scoop. DeMambro has been searching for more power for his '04 Z06 for some time now, and he's learned some important lessons in the process.
A few years ago, DeMambro decided it was time to get that one special car he he'd always wanted. He had an '02 Mercedes-Benz AMG ML55, but it just didn't deliver the bang for the buck he was after. When he decided to upgrade to the top-of-the-line SL, the M-B dealer experience sent him running to his nearest Chevy vendor. The folks at Walter Earl Chevrolet were much more accommodating and didn't mind letting their new black Z06 off the lot for a testdrive. DeMambro found the sound and feel of the car to be simply awesome. By the end of the ride, he was an official Corvette nut.
Once DeMambro got the car home, he began to feel that maybe it wasn't quite as exotic looking as he had wanted. Then, while browsing through an aftermarket parts catalog, he came across the Greenwood G5 body kit. A few phone calls later, and he'd arranged to have the kit installed in Greenwood's shop in Apopka, Florida. DeMambro and his wife dropped the car off with Tim and Joe Greenwood and went on to enjoy a week in the Florida Keys. When they returned, the car was ready to go. It was only the second full G5 body kit the company had installed.
The drive home proved revealing. On the trip to Florida, DeMambro had noticed some wind buffeting when he got close to large semi trucks. On the return trip, the buffeting wasn't there. Also, during a period of wet weather, he realized that all the drivers passing him were giving him the thumbs-up sign. Apparently, the rooster tail being raised by the Greenwood rear-valance air-management system was really getting their attention. This was obviously one aero kit that really worked.
Once the car was home, DeMambro couldn't resist taking it to a few shows. The most interesting event was an NCRS show at the Lars Anderson Museum in Brookline, Massachusetts. DeMambro wasn't sure what kind of the reception he might receive, as this was an official NCRS chapter meet. To his pleasant surprise, the organizers gave him a warm reception. DeMambro's car was such a hit, in fact, that another attendee decided to pop for the G5 package for his own Vette.
The next thing DeMambro noticed was that everyone wanted to race him. The first serious challenge wasn't long in coming. Shortly after the next show, as he was driving out of town, DeMambro heard a deafening roar as a Hennessey Viper pulled up beside him. With a few words, it was agreed that there would be a short "vehicle dynamics" test. Out of the hole, the Z06 pulled the Viper in the first two gears. Shocked at being ahead, DeMambro looked back to see where the Viper was and forgot to shift. The rev limiter kicked in, and the Viper jumped ahead before DeMambro could shift into Third. With the Viper ahead by three lengths at well above the speed limit, both drivers finally backed off.
Later, DeMambro figured out a couple of things. First, the Viper had been supercharged, giving it a huge power advantage in the higher gears. The other thing he remembered was that he hadn't put his car in Competition mode, so the dynamic stability system had been engaged the whole time. The traction-control component had helped him get all of the car's power to the ground. It had also helped him combat the small sand drifts that intrude on the edge of the highway. All of this made for an epiphany. Clearly, the car performed well, and the electronics were effective in getting power to the ground, but something more was required. The search for big-league performance-and the start of a few more lessons-had begun.
DeMambro began looking at superchargers, eventually settling on a Blowerworks system designed by noted forced-induction expert Greg Carroll. The system was gaseous intercooled, solidly built, and came with a water/alcohol-injection system to control detonation. DeMambro enlisted Harbour Chevrolet's Dave Belmore, a technician with considerable performance experience, to perform the installation.
The job went smoothly, but the first dyno run was a huge disappointment-only 425 hp at the rear wheels. Belmore adjusted the fuel mix and timing and, with a little fiddling, the car pulled nearly 500 rwhp. At the dragstrip, the blown Z ran 12.4s at 124 mph on street tires, but during one of the runs, it let out a big puff of white smoke. Later, it was determined that the dipstick had been pushed out, and oil had sprayed everywhere. After a few more runs, the clutch overheated and wouldn't disengage.
In retrospect, DeMambro figures this was probably the beginning of the end of the first engine. Still, the car seemed to be running well, and it wasn't raced again for the rest of the year. The weak links were upgraded; the clutch was changed to a Centerforce unit, and the stock tires were replaced with Nitto NT555R performance rubber.
Then, while pulling out of a gas station, DeMambro noticed a huge cloud of white smoke billowing from the engine compartment. Checking the engine, it became clear that oil was coming out of the oil-filler cap and covering the hot exhaust system. Somehow the oiling system was getting pressurized, possibly the result of a PCV valve that had been installed backwards.
By this time, DeMambro was coming to the conclusion that something else wasn't quite right. Sure enough, during a compression check, it was discovered that the No. 7 cylinder was down to 75 psi, instead of the normal 150 psi. DeMambro realized that his decision not to upgrade the stock pistons, rods, and crank at the time of the blower install was finally coming back to haunt him. It was time to pull the engine and see what was going on.
When he saw the pistons, it became clear what had happened. The oil-ring lands in two of the eight cylinders had been partially blown off. Hence, the drop in compression. However, since the block and heads weren't damaged, DeMambro made the decision to update the bottom-end internals instead of replacing the entire motor. It was cheaper, after all, and it addressed the underlying problem.
The stock crank was deemed adequate, but Eagle H-beam forged rods and Mahle forged pistons (complete with valve reliefs to lower the compression ratio) were subbed in for their factory counterparts. The head bolts were replaced with studs, the exhaust ports were port-matched, and the cam was updated with a GMPP unit boasting slightly more duration and lift. All of the work-including the final balancing-was performed at All Cape Machine in Hyannis.
This time, DeMambro turned to Dez Racing in Seekonk for tuning. After a disappointing initial dyno pull of 325 rwhp was traced to fouled plugs, a backup run put the tally at 423 rwhp-better, but far off the car's previous best of almost 500.
Dez Racing owner-operator Don Kinder deduced that DeMambro's engine modifications had actually lowered the LS6's compression too much. He suggested lowering the timing, which would allow the engine to safely accept 10-15 psi of boost. This, in his opinion, would really allow the supercharger to shine.
Kinder obtained new, smaller pulleys to generate the extra boost. Because the standard six-rib belt and accessory drive were designed for no more than 10 psi, Greg Carroll recommended a new eight-rib unit along with a stronger tensioner to reduce belt slippage.
At the time I visited DeMambro, these pieces hadn't yet been installed. So when he invited me to drive it, I wasn't quite sure what to expect. DeMambro is a sly dog, though, and although he had been filling me in on all of his various travails with the car, he knew that the package was still plenty impressive. He handed me the keys, and we were off.
While I'd driven older cars with big horsepower, I'd never had a chance to unleash a Z06. And a Z06 with a supercharger-even at lower-than-ideal boost-was something significantly beyond my experience. DeMambro had any number of descriptions for it, all of them involving the unbridled thrill of the overall experience. "It takes you back to being a teenager-but not an especially intelligent one," was a favorite.
Leaving Falmouth and entering the divided section of highway that leads to Boston, it was time to do my own version of DeMambro's vehicle-dynamics test. Rolling onto the highway in Third gear (in First and Second, the car just spins its wheels), it was time to cut loose. I eased into it, and cars in the slow lane just disappeared behind us. It wasn't long before DeMambro brought me back to reality by saying, "You better slow down; the cops hang out just ahead."
We played for a while longer, then took the car back to DeMambro's house to reflect on the experience. He told me that the search for power wasn't as easy as most people think, but when you get it right, it really is right. Having sampled his car's extraordinary performance firsthand, I couldn't agree more.