1970 AMC AMX - Dream Team
He tunes, she drives, and both scheme up ways to make their 8-second AMX even faster. Where do we apply?
From the February, 2009 issue of Popular Hot Rodding
By Stephen Kim
Photography by Robert McGaffin
Whether momma needs a new pair of shoes, or daddy needs a new pair of project cars, to say that the resulting purchase is co-owned by both parties is a smelly pile of nonsense. That's why we get a kick whenever a reader tells us that his hot rod is owned by him and his wife. Please. As if the poor schmuck is out showing off his wife's pumps to his buddies and claiming that they're his own. We have yet to encounter a husband and wife duo whose interest in a project car extended beyond their shared bank accounts, until a freakish turn of events at Route 66 Raceway. First, we watched in awe as a wheelstanding AMX laid down an 8.89-second pass at 153 mph. Then, climbing out of the car in the pits was a slender young lady. In an odd reversal of roles, it was the husband playing cheerleader at the starting line, and the wife doing the driving. Now this, folks, is the real deal.
Typically, the best a man can hope for is a wife who merely tolerates his wrenching proclivities, and begrudgingly shows up at shindigs for moral support from time to time. In the case of the Erbs, racing is a genuine symbiosis. Steve has always been big into Chevys and Pontiacs, routinely giving his '70 Chevelle and '69 LeMans beat-downs on the street and at the track. Ann, on the other hand, is an AMC aficionado to the core. "My aunt taught me how to drive in a Gremlin when I was 14, and my mom had a Cherokee, so I guess I was destined to have a thing for AMCs," Ann explains. "I bought a '75 CJ Jeep with a 304 AMC motor and a three-speed when I was 17, and got into four-wheeling. I've always thought that a Jeep should have an AMC motor." Interestingly, Ann was the black sheep of her family, the only one who viewed cars as anything other than simple transportation. Consequently, it was only appropriate that she ended up marrying a fellow enthusiast. Sharing a common gearhead gene, the couple helped diversify each other's automotive interests. Ann passed her passion for AMCs on to Steve, and Steve in turn opened her eyes to the world of drag racing. After Steve bought his wife a book on the history of AMC, the blueprint for the future really started taking shape.
NMCA rules ban adding metal...
NMCA rules ban adding metal or epoxy to the cylinder heads and intake manifold, which makes the AMX's 900-plus-hp output even more impressive. Dry-sump oil systems are also prohibited, so builder Barry Allen bolted a belt-driven pump to the mill using a drive system adapted from a big-block Chevy. To optimize sealing with low-tension rings at high rpm, a vacuum pump evacuates the crankcase of fumes. Inside the block are roller cam bearings.
"I saw a picture of a two-seat AMX in the book, a model that I'd never seen before, and knew I had to get one," says Ann. "In addition to my full-time job, I had to work two other jobs in order to save up enough money to buy one. A friend of ours had a 10.5 drag car, so we wanted to get in on the action too. We felt that head's-up classes were too expensive to compete in, so we decide to bracket race instead."
After months of searching, the Erbs found a clean '69 AMX with a mild 401 that ran mid-12s out of the box. After dialing in the motor and some more time behind the wheel, Team Erb whittled the e.t. down to 11.71 within the first season of racing. Over the course of seven years and three different engine combos, the AMX ran a very respectable best of 10.19 at 131 mph.
Bracket racing success notwithstanding, the Erbs pined for a new challenge. "We knew we wanted to race in a head's-up, small-tire class, and it had to be in an AMC," says Ann. So when the Erbs found a '70 AMX online that had already been set up as a drag car, they pounced. "At first we thought it was out of our budget, but after taking another look and postponing some home improvements we had planned, we decided to buy it in January 2007. It had a lot of high-dollar parts on it that were useable, but overall, the car was not executed to our liking, so we took it completely apart. We redid the wiring, rollcage, suspension, interior, and driveline with the help of our good friend Tory Shellehamer in about eight months."
The reason the AMX doesn't look the part of an 8-second monster is a matter of law. Steve and Ann campaign the car in both NMCA Pro Stock and their local RAM racing series, both of which have very similar rules mandating a stock-like appearance. In addition to forcing competitors to run tiny 10.5-inch tires and full interiors, the classes ban tube chassis, and the Erbs have chosen to pass on a power adder in favor of a weight break. That's right, the 2,800-pound AMX blazes the traps at 153 mph with just 435 naturally aspirated cubic inches, a feat that requires turning nearly 9,000 rpm.
Not only are those figures astonishing, they're nearly impossible to achieve even in a platform as venerable as the small-block Chevy. So what's the trick to straining the water brake to the tune of 900 hp with an AMC motor? Steve says that like the Pontiacs that he adores, an AMC motor is neither a small-block nor a big-block. It's just an AMC. Consequently, the AMC's enormous 4.750-inch bore spacing yields tremendous flexibility when tailoring cylinder dimensions to specific race applications. Furthermore, a small but extremely hardcore group of AMC racers over the years has persuaded the aftermarket to pump the latest cylinder head innovations into the AMC platform.
Built by AMC expert Barry Allen, the hyper-oversquare 435 features a heroic 4.380-inch bore and a shorter-than-a-383-Chevy 3.605-inch stroke. The rotating assembly consists of a custom Moldex billet crank, Manley 6.000-inch steel rods, and forged 15.0:1 Diamond pistons. It's all anchored in place in an Indy Cylinder Head aluminum block. While Barry won't disclose exact camshaft specifications, he says that duration and lift are in the 280/290-at-.050 and .875-inch ranges, respectively. With an 8,800-rpm power peak and 435 hungry cubes to feed, the Big Kahuna in the equation is the cylinder heads. Meeting the challenge is a set of Indy 401-1 aluminum castings that boast Rat-like 300cc ports and 2.30-/1.75-inch valves. With Indy's CNC porting, the heads flow 360 cfm out of the box, but after Barry gets done with them, the figure jumps to 425 cfm at .850-inch lift. Jesel shaft-mount rockers, and COMP offset lifters and tapered pushrods maintain valvetrain stability.
Granted, Ann's bracket car was plenty quick in its own right, but stepping up to an 8-second machine has been quite an experience for both her and Steve. "We're still in the middle of a steep learning curve," says Steve, who's in charge of tuning the chassis and motor on race weekends. "This isn't something you can just get into and start racing at 100 percent, especially since the NMCA doesn't allow wheelie bars. We've found out pretty quickly that track temperature is a key element in how you set up the chassis. If tire pressure is too low, you'll scrape the back bumper, and as track temperature increases, it's critical to keep playing with tire pressure and the timing. Our best 60-foot to date is a 1.29, but we'd like to get that into the mid-1.20s."
The view from the driver seat isn't short of excitement, either. "Compared to our '69 bracket car, you feel the difference in power the most on launch and when going through the traps," Ann explains. "The first time we had the 10.5 car out, the chassis setup was conservative, so it didn't launch any harder than the bracket car. It didn't feel any faster by half track, but once I shifted into high gear it felt like I hit a nitrous button. By the time I crossed the traps, I was saying stuff inside the car that you can't print in the magazine."
As any racer knows, what goes down at the track is just part of the lifestyle. For Team Erb, you could make the argument that their common passion further fortifies their spousal bond on a daily basis. "We're constantly talking about how we can improve the car and make it faster," says Steve. "It doesn't matter whether we're eating breakfast, at work, at the track, or at a friend's house. Every day, we're constantly coming up with new schemes, and we spend a ton of time together racing, at shows, and working on the car." Like the Erbs say, they're both co-owners in this venture, and they really mean it.
NMCA Pro Stock
To most drag racers, Pro Stock elicits images of bland, amorphous, fiberglass-bodied cars that are as entertaining to watch as C-SPAN. And it's a damn shame, since the class is powered by what is arguably the pinnacle of V-8 engine technology. Nonetheless, NMCA's version of Pro Stock is more like NHRA Super Stock on crack. Rules dictate that cars must retain a stock appearance, which calls for full interiors, stock framerails, glass windows, 10.5-inch tires, and stock- or ladder-bar-type suspension. All motors must be naturally aspirated with mass-produced cylinder heads and intake manifolds. Both big- and small-blocks are legal, with minimum curb weights-ranging from 2,700 to 3,550 pounds-based on displacement. Furthermore, all cars must run mufflers. To keep the action more grassroots, clutchless manual transmissions and pneumatic shifters are banned. In other words, NMCA Pro Stock is hot, its cars are real, and while it isn't cheap, you certainly don't have to be a pro backed by corporate sponsorships to play. -Stephen Kim
According to Steve, a stock...
According to Steve, a stock AMX tips the scale at roughly 3,200 pounds, and the Erbs' drag car comes in at 2,800 pounds in race trim. Removing that much weight while retaining a stock appearance is no easy chore. "We're allowed to run an aluminum block and a fiberglass hood and bumpers, which helps a lot, but that's about it," says Steve. "Little things like gun-drilled axles, titanium wheelstuds, removing brackets that you don't need, and drilling holes where you can, starts adding up. It sounds silly, but the idea is to lose a half-pound here and a half-pound there. We think we can remove another 50 pounds from the car."
One of the most time-consuming...
One of the most time-consuming parts of the buildup was cutting out the old rollcage and installing a new one. The Erbs work at an industrial fabrication shop, and have access to tools that came in handy during the process. "We have friends who have very advanced fab skills, and learn a lot from them along the way," says Steve.
In August 2007, Ann had a...
In August 2007, Ann had a run-in with the wall at Cecil County Dragway. Fellow racer Dave Coleman-who owns Purnell's Body Shop in Elkton, MD-towed the AMX back to his shop and fixed it in just two weeks. He never asked for a cent. The Erbs would like to say thanks to Dave, Erica, and everyone at the shop. "There were times we both had tears in our eyes from the generosity of other racers. That whole event could have turned us the other way, but because of them, we still have a positive attitude and are still racing," says Steve.
The AMX's previous owner had...
The AMX's previous owner had already installed the rear ladder bars, but the Erbs repositioned the suspension mounting points. During the off-season, plans call for replacing the Dana 60 with a lighter 9-inch rear. The goal is to shave a few hundredths off of their 60-foot times.