Big Bad Ballistic - 1970 AMC AMX

The whys and wherefores of AMCs remaining relative bargains among the muscle-minded have been discussed innumerable times in these pages. Suffice it to say, if you want to go fast, Kelvinator parts may cost more, but the car itself could be a bargain. The cost involved with hopping things up comes out in the wash.

Break down the numbers, and it's enough to do a collector's head in: Just 4,116 AMXs were built for 1970, the final season of the two-seat bodystyle (part of that could be due to the $4,202 base price; four grand for a Rambler was a bit of an eye-opener in those days). Of those few AMXs built, 1,632 came with the 325hp, 420-lbs.ft. 390/four-speed combination--the stoutest bit of business AMC offered in a production car in 1970. The colors were as psychedelic as any other marque's, and the power every bit as fierce...yet somehow, AMCs are not made of unobtanium, like LS6 Chevelles or their ilk.

But for some, owning an AMC is destiny. Kirk Fletcher of Peoria, Arizona, found this Shadow Masked '70 AMX languishing in Dallas, Texas, back in 1994. "My dad drove a 1968 390/four-speed AMX for years and he sold it to me in 1976 for $1,200. I restored his old car with an engine rebuild with the Group 19 dealer speed parts and a new paint job and factory stripes. I drove that car as my daily driver for a few years while in college, until I sold it to pay for a '71 Triumph TR6 that I had bought.

Cold-air Ram Air tub seals to the hood, feeding the 800-CFM Edelbrock-built AVS-style carb; chrome trim accents AMX's factory-stamped contours.

"I always wanted another AMX, and the '70 had always been my favorite year. The body was clean and straight on this one, and it still had the original factory Hialeah Yellow paint. It had all the right options that I wanted: 390 Ram-Air, four-speed, 3.54 Twin Grip, power disc brakes, power steering, 'Machine' wheels, and it came with the original window sticker, build sheet and the warranty ID card. A $3,000 purchase price was icing on the cake."

For half a dozen years, Kirk used it as a semi-regular driver, taking it down the quarter-mile and through the occasional autocross. And then, disaster: "At our first annual Cactus Classic AMC car show, I broke a piston on the dyno. It was April Fools' Day, 2000." Kirk wasn't laughing.

So began the long and arduous process of getting the car back on the road.

The decision, early on, was to get it on the hairy end of streetable--but to make it look as stock as possible. That meant using the stock cast-iron AMC block and head castings, but with some tweaks.

Attractive and rarely seen 15x7 Rebel Machine wheel was also an option on AMXs in 1970.

The .040-over TRW pistons, dished .017-inch, required the deck to be milled .060-inch, while the heads needed .024-inch milled off to obtain the 10.7:1 compression the engine now enjoys; this also required the newly added Edelbrock Air Gap intake to be trimmed a whopping .084-inch to fit. Rather than have the aluminum intake stand out beneath the Ram Air tub, Kirk decided to paint it AMC engine blue, same as the rest of the block. It's hard to imagine that a car that looked like this would need to trade in stealth tactics, but there you go.

Owner Kirk Fletcher

Those stock 1970 casting heads are now full of 2.02/1.625-inch valves, Precision Valve Systems 1.7:1 roller rockers, and dual Pontiac valve springs from Dana, by way of NAPA. The cam is an AMC hydraulic flat-tappet grind made by Dana for NAPA--offering .508-inch valve lift with the 1.7 roller rockers installed. An 800-CFM Carter AVS four-barrel rests between that secret performance intake and the air cleaner, with its outer tub sealed to the top of the hood in true Ram Air fashion.

Along the way, all of the factory castings and forgings were de-burred, and the crank and rods were shot-peened. The forged-steel crank, formerly an externally balanced unit, was converted to an internally balanced piece with 312 grams of Mallory metal. To maintain high-RPM oiling, Kirk started with an 8-quart Milodon pan, added a lifter-valley oiling line and opened up all oil passages in the block and heads. Bottom-end hardware is all ARP. The machine work on the block and heads was done by the Phoenix NAPA DC machine shop, while cleanup of the internals was performed by the Glendale NAPA machine shop.

Indeed, with the air cleaner on, the most obvious upgrades revolve around the exhaust: Ceramic-coated Hooker Super Comp long-tube headers hang fairly obviously beneath the chassis, though they don't hang lower than the front crossmember and so are unlikely to be smashed; a Pypes X-crossover, 3-inch pipes, Flowmaster 40 mufflers, and 2 1/2-inch tailpipes (hung with reproduction AMC hangers, thank you) unleash a racket unlike any you've heard on a street AMX.

Other details have been shifted around in the engine compartment. The power steering pump and bracket are Saginaw units, pirated from a '72 AMC. The washer bottle and coolant-recovery bottles also came from newer models. The fan shroud was from an air-conditioning-equipped AMX; with desert temps running as high as 120 degrees in the summer, it pays to keep cool--and a proper fan shroud helps.

The result? On paper, it depends entirely on how much stock you put in the software of the Desktop Dyno 2000. Stock, an AMC 390 was rated at 325hp and 420-lbs.ft. of torque; with the mods outlined here, the software claims 498 at 5,700 RPM, and 503-lbs.ft. at 3,200 RPM. The 13.28 @ 107 MPH trap time, combined with the granny-level 2.18 60-foot time, suggests that a set of slicks should vault Kirk well into the 12s, and make for ETs that come a little closer to validating that horsepower number. "I had to leave the line at 650 RPM and ease into the power to keep from spinning the tires," he confirms for us. "I'll be buying drag radials sometime this spring." Which means about the time you read this. Watch out, Phoenix.

A Hurst Competition Plus shifter and a Centerforce Dual-Friction clutch allowed the '67-era AMC-spec Borg-Warner T-10 four-speed--and its hairier-than-most 2.64:1 first gear, a big step up from the 2.23 first that came stock in the AMX--to do its good work, getting sufficient twist out to the Twin-Grip 3.54 gears in the AMC 20 rear axle.

Other minor chassis tweaks fall under the easy-factory-upgrade category: the newer Saginaw variable-ratio power steering system, stock leaf springs fortified with extra leaves for more Trans Am-like cornering, heavy-duty-type coils in front. Save for the anti-roll bar and the gas shocks, most of what's here is AMC. That includes the 15x7 Machine wheels, which are a refreshing change from the Magnum 500-type wheels we generally see; they make the 245-section BFGoodrich tires in front look far fatter than they otherwise might.

Our cursory drive came a little closer to revealing the truth behind this car's capabilities. At the 600 RPM idle, the exhaust rumble filled the cabin, and the aggressive cam placement meant we could practically count the valves as they slammed shut. Pulling power was tremendous from 1,500 RPM clear through redline, although exhaust resonance cut through the cabin between 2,700 and 2,800 RPM. Luckily, we weren't there for long: On surface streets, the engine rips through the revs so quickly that you'd better shift 700 RPM early so you're in the next gear by the time the engine hits redline, and a steady 75 MPH on the freeway is good for 3,000 RPM.

Inside, we approved of the addition of the '72-era wheel. The perforated vinyl seating areas in the chairs don't offer much side support, but let you sink in nicely. A stiff clutch pedal made up for itself by engaging near the top of the pedal's travel, and while the fore-and-aft motion of the shifter is surprisingly long, the 2-3 shift across the gate requires little lateral travel; you almost feel like you're shifting back into first, except the mechanism has the sense to help you into the right gear. On the highway, we found the stiffened suspension a tad jouncy for our liking, but that was mitigated by the solid, flat cornering. Despite the GM-based components, the power steering felt Mopar-esque: heavily boosted and heavily medicated in equal quantities; it was the only characteristic that announced itself as not being integral with the performance program.

But no one can drive a car like its owner, and when Kirk hopped behind the wheel, we went sliding sideways out of his street and onto the main drag; engine noise was so present that you could barely even discern its march up the revs until Kirk slammed it into another gear. Rubber into second...and into third? Egads. Suddenly, the super-light power steering made sense--all the better to catch the back end under feats of full-throttle derring-do. Maybe those 500hp estimates are closer to the truth than we realize.

And yet, this was just the first step. "Once the engine was completed, three years later, the engine compartment looked terrible, so I figured that I would paint it. But I felt that I should rebuild the front suspension first. Then Brian, the owner of the [now-defunct] Arizona Autocrafters body shop said he needed some work and would give me a good deal."

And so the slippery slope of approaching physical perfection begins. "I stripped the car down in two weeks and towed it to his body shop. I ended up rebuilding and restoring everything." The body was brought back to stock specification using patch panels on both lower rear quarters; everything else was original and mercifully rot-free. The Hialeah Yellow paint was DA-sanded down to bare metal, while the greasier engine compartment was media-blasted clean.

At this point, Kirk authorized the switch to Big Bad Green: three primer coats, then three color coats, wet-sanded in between and followed with three coats of clear (all PPG enamels), which were then color-sanded and buffed. The Shadow Mask was reapplied, and a quarter-inch strip of 3M silver tape separated the colors. You have to touch it to know it's tape: it looks like paint, it's so smooth. Stainless pieces were polished, the bumpers were re-chromed, and other chrome items were brought back to life with 0000 steel wool.

The interior was given options that it either never came with or were never offered: The aforementioned 1972-era vinyl-wrapped steering wheel and a cueball for the shifter are the obvious changes, but Kirk also added an AM/FM pushbutton radio, tilt wheel, tinted glass all around and, of course, the older four-speed transmission mentioned earlier. These things have a way of getting out of hand. "It took a little over 10 1/2; years from the time I started until I was able to drive it again," he laments.

Today, Kirk is engulfed in AMC and Rambler projects: A pair of V-8 Rogues grace his driveway (including a 343 four-barrel, four-speed 3.54 Twin-Grip convertible) and a factory-built '71 Hornet SC/360 with Ram Air, Go Pack and four-speed with 3.54 Twin-Grip rear that's been painted a correct-but-not-for-this-car plum. And yet, it's the AMX that still moves him, literally and figuratively, after nearly two decades of ownership.

"This car is the one that fits me the most, both physically and mentally. It is so much fun to drive; I always get a smile on my face as I leave a bit of rubber on the pavement and the rear quarter panels. I find that it is almost impossible for me to drive this car without getting rubber on the quarter panels. My wife drove the car to the photo shoot so it would stay clean for the pictures."

OWNER'S VIEW

It took me two weeks to get it on the road after I bought it in 1994, and I started driving it as-is until I broke the piston. I drag-raced the car for five years at Speedworld here in the Phoenix area and hadn't broken anything, but its first time on the dyno at UTI, I broke a piston. Go figure!

I have had several AMCs over the years, mostly AMXs, Javelins and Americans. I can jump in it at any time and drive it hard and it puts a big smile on my face. I can also open the door from the house to the garage and just stare at it, and it makes me feel good just looking at it.

- Kirk Fletcher

PROS

+ Nicely optioned from the factory

+ Rubber in the first three gears

+ Fairly cheap to get into

CONS

- One of 4,116 and no longer original

- Choppy highway ride

- Power steering is Chrysler numb

1970 AMC AMX Specifications

Engine

Block type -- AMC "second-generation" V-8, cast-iron, decked .060-inch

Cylinder heads -- AMC "dog leg," casting number 3196291C, 50.6cc chambers (before porting), decked .024 inch

Displacement -- 390-cu.in.+ .040-inch overbore

Bore x Stroke -- 4.205 (4.165 + 0.40) x 3.574 inches

Compression ratio -- 10.7:1

Pistons -- TRW forged-aluminum, dished

Connecting rods -- Stock forged-steel I-beam

Horsepower @ RPM -- 498 @ 5,700 (estimated)

Torque @ RPM -- 503-lbs.ft. @ 3,400 (estimated)

Camshaft type -- Hydraulic flat-tappet, produced to AMC spec by Dana Corp.

Duration -- 222 degrees intake/exhaust (at .050)

Lift -- 0.5083-inch intake/exhaust

Separation -- Angle 108 degrees

Installed -- Four degrees advanced

Valvetrain -- NAPA/Dana 2.02/1.625-inch stainless valves, Precision Valve Systems 1.7:1 ratio roller-rocker arms, NAPA/Dana dual-valve springs for Pontiac, NAPA/Dana AMC anti-pump lifters

Fuel system -- Edelbrock RPM Air Gap intake, 800-CFM Carter AVS four-barrel carburetor, mechanical Carter fuel pump

Lubrication system -- Milodon 8-quart oil pan, crank scraper and lifter-valley oil line added

Ignition system -- MSD Pro Billet distributor

Exhaust system -- Ceramic-coated Hooker Super Comp headers (1-7/8-inch primaries), Dynotech merged collectors, 3-inch Pypes stainless X-crossover, 3-inch exhaust pipes, twin Flowmaster 40 mufflers (3-inch in, 2 1/2-inch out), custom-bent 2 1/2-inch aluminized steel tailpipes

Original Engine -- AMC 390-cu.in. V-8

Transmission

Type -- Borg-Warner T10, 1967 AMC wide-ratio gearing, 10.5-inch Centerforce dual-friction clutch, Hurst Competition Plus shifter

Ratios:

1st -- 2.64:1

2nd -- 2.10:1

3rd -- 1.49:1

4th -- 1.00:1

Reverse -- 2.55:1

Differential

Type -- AMC Model 20, 8-7/8-inch ring gear, factory Twin-Grip limited-slip

Ratio -- 3.54:1

Steering

Type -- Saginaw recirculating-ball with 1972 Saginaw power-steering pump, 3.2 turns lock-to-lock and 32.8-foot turning circle

Ratio -- Variable (12.0:1 to 16.0:1)

Brakes

Front -- AMC 11.3-inch vented disc by Kelsey-Hayes, power assist

Rear -- AMC 10x2-inch cast-iron drum with station wagon cylinders

Suspension

Front -- Factory heavy-duty AMC coil springs, ADDCO 1 1/8-inch anti-roll bar, Gabriel three-way adjustable gas shocks

Rear -- Factory heavy-duty AMC semi-elliptic leaf springs, factory torque links, Koni three-way-adjustable shocks

Wheels & Tires

Wheels -- AMC "Machine" wheel

Front -- 15 x 7 inches

Rear -- 15 x 7 inches

Tires -- BFGoodrich Radial T/A

Front -- 245/60R15

Rear -- 255/60R15

Performance

Acceleration 13.28 seconds @ 107 MPH; 2.18 60-foot