When the subject of fast, late-model street machines comes up, Vettes, Vipers, Buicks and F-bodies will be named and even a few Fords are bound to be included as contenders. Those are the obvious choices, but how often do GMC Syclones and Typhoons get mentioned? That depends on the crowd. There is no doubt their all-wheel drive configuration and boosted V-6 powerplant combined for a potent combination from the factory, but that was more than ten years ago. Total production for both trucks never even reached 10,000 units and they are an even rarer sight now. Besides, their aerodynamically challenged bodies and aging drivetrain are no match for Detroit's current offerings, right?
If you're looking for a race and you have that mindset, you'd better stay away from these trucks, especially the black '91 Syclone owned by Dr. James (Doc) Hoover and his son, Matt. In the years before little Hoovers started running around Doc's house in Adamsville, Tennessee, he held the NHRA SS/L class record for four straight years with his small-block Chevy II. Family commitments put Doc's racing career on hold, but as his sons reached a more manageable age, Doc finally jumped back into the game and picked up right where he left off.
He still wanted to own the quickest ride around, the only difference was his platform of choice this time was going to be an all-wheel drive truck. "Everyone is always trying to build a fast street machine and you usually have to do all kinds of stuff to make the cars fast. I figured, why not have something you can just roll up in and say, 'Are you ready to race?' and you'd be ready," says Doc. A Syclone was exactly what Hoover had in mind--no nitrous bottles to deal with and no tire swaps or air pressure adjustments to be made, just lots of boosted power and the traction advantage of AWD.
The Hoovers' quest began with a nearly mint, 2,800-mile Syclone they picked up in Ohio and promptly delivered to a speed shop for a complete overhaul. The initial build did not meet their expectations, so Doc then connected with Dan Strezo and Harry Hruska at Precision Turbo and Engine in Hebron, Indiana (Dan now owns and operates D.L.S. Engine Development in Wheatfield, Indiana). "I did a little searching and talked to some people who told me they were the best at building these turbo engines," says Hoover. Doc's goal was pretty simple--he wanted to run as fast as he possibly could, while keeping breakage to a minimum.
The centerpiece of this plan was a 4.3-liter Bowtie block, which was bored .030 over and enhanced by a 72mm Garrett turbo, which produces 26 pounds of boost. Strezo packed the block with stout internals to handle both the massive boost and subsequent abuse Doc would throw at it. This list includes an odd fire steel billet crank, JE pistons, Oliver connecting rods, Comp pushrods and a custom-ground cam that Dan didn't want to discuss at all, other than to say he got it from Comp. Ruske tuned the beast to perfection and Doc quickly found his new baseline was in the mid-11-second range.
Subsequent trips to the track made it clear Strezo had built a V-6 capable of propelling the 3,400-pound truck into the 9s, but Doc and Matt soon realized the biggest obstacle standing in their way might be the same AWD system that helped the truck hook up so well on the street. Many of the quickest Syclone owners have found the added weight of the AWD system negated the traction benefits and actually slowed their quest for lower ETs. The Hoovers debated whether they should stay with the factory configuration and ultimately, the goal was set to be the first AWD Syclone in the 9s.
Once that problem was solved, the Hoovers could concentrate on the rest of the handling and suspension issues they faced. "The biggest difference between AWD and two-wheel drive is handling the thing out of the gate. When you've got those locker rear ends in that thing, if it ever spins one of them a little more than the other, it gets really hard to handle, especially in the first 60 feet," says Doc. "When it gets wild, it gets really hard to correct and you just have to get out of it."
A four-link suspension was given some thought, but at the suggestion of Mike Callahan, a set of Flex-A-Form fiberglass springs were purchased to go with a Caltrac traction bar system. "I cut those springs and it dropped the truck right down and also lightened it up a bit too," claims Doc. To combat weight transfer issues in the front, a custom coil-over suspension system was installed from Precision Engine & Performance. "I had to figure out a way to hold the front end down, because we've got to have the front tires for it to leave. The coil-over was wonderful for that and our problems went away once we could adjust the weight transfer," says Doc.
The Hoovers' pursuit of a single-digit pass was relentless and although the engine stood up well to the demands placed on it, the same could not be said for the transmission. "The 700 just wouldn't stay in it. It took about three runs and we'd waste second gear," says Doc. Eventually, it was replaced with a more durable turbo 400, built by Wayne's Transmission in Waynesboro, Tennessee.
Looking back on his progression, Doc claims the toughest jump came in getting the truck into the 10s; an achievement he credits to their suspension upgrades. Once they broke through that barrier, they steadily tweaked and tuned their way down to 10.30s, at which point Doc asked Strezo for his assessment of the situation. "He told me that might be all I was going to get out of it. He knew the motor was making the power for 9s, but I had to figure out how to get it to the asphalt, so that's what I went to work on," says the elder Hoover.
The truck was running straight as an arrow, but it was smoking the tires 100 feet out. After mulling over his options, Doc finally decided to make a change that propelled the truck into the single digits. "One day I told Matt we were going to cut the boost back and it just instantly picked up," says Hoover. The Syclone is still running 26 pounds of boost at the top end, but things are now much tamer coming off the line. "I've got two boost controls. One controls it on the line and once you let off the brake, it changes over to the other boost control. About one second after I let off the brake, it goes from 10 pounds up to 26," explains Hoover. "That was the easiest thing we ever did to pick up ET and it was good for three tenths."
Those three tenths have put the Hoover's Syclone in front of the pack of known contenders, making it the world's fastest AWD Syclone. Matt made the magic pass of 9.89 at 137 mph, which has once again moved a Hoover to the forefront of their peers, just as Doc had done with his NHRA SS/L class record more than 15 years ago. In spite of that success, thoughts of making more changes are still being discussed and the Hoovers have even considered selling the truck, but neither has happened yet. "It will run almost as fast on the street as it does on the track and it's the world's fastest AWD V-6, so why not stay with it?" asks Hoover. Perhaps the appeal of a new challenge will force a sale or maybe they will continue to push the envelope with their current ride. Check out www.dochoover.com to see what they ultimately decide.
| DATA FILE |
| Truck: | 1991 GMC Syclone |
| Owner: | Dr. James and Matt Hoover |
| Block: | 4.3L V-6 Bowtie block, 280 cubic inches |
| Compression ratio: | 8.5:1 |
| Heads: | Brodix, 2.08/1.60 Manley valves |
| Cam: | Comp, custom grind by D.L.S. Engine Development |
| Pushrods: | Comp |
| Rocker arms: | 1.55:1 ratio |
| Pistons: | JE |
| Rings: | Seal Pro |
| Crankshaft: | odd fire Steel Billet |
| Rods: | Oliver |
| Throttle body: | Accufab |
| Fuel Injectors: | 160 lb./hr. |
| Fuel pump: | 2 Bosch inline |
| Engine management: | FAST |
| Power adder: | Garrett 72mm |
| Boost: | 26 psi |
| Intercooler: | Custom fabricated by D.L.S. |
| Wastegate: | HKS |
| Exhaust system: | Kenne Bell 1.75-inch headers, custom-fabricated 3-inch downpipe, 3-inch single exhaust with Flowmaster muffler |
| Transmission: | Turbo 400 |
| Torque converter: | Precision, 4500-stall |
| Driveshafts: | Stock front, Quartermaster aluminum rear |
| Front suspension: | Precision Engine & Performance custom coil-over shocks, Bilstein springs |
| Rear suspension: | Flex-A-Form fiberglass springs, Rancho adjustable shocks, Caltrac traction bars |
| Rear end: | Stock, with a TA Performance girdle and 3.42 gears |
| Brakes: | Stock brakes, Kirban soft compound shoes and pads |
| Wheels: | HRE custom 3-piece |
| Front tires: | BFGoodrich drag radials, 275/40-17 |
| Rear tires: | BFGoodrich drag radials, 315/35-17 |
| Fuel octane: | 116 |
| Race weight: | 3,420 lbs. with driver |
| Best ET/mph: | 9.89 at 137.17 mph |
| Best 60-ft. time: | 1.51 |
| Current mileage: | 4,853 |
| Miles driven weekly: | 10
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