This '66 GTO may seem like...
This '66 GTO may seem like an ordinary Pontiac, but what lies under its Ram Air hood is extraordinary. Owner Mark McConville of Birmingham, Alabama, purchased it in 2004 off an Internet website shortly after a complete body-off restoration had been performed. It was recently converted to compressed natural gas (CNG) operation.
Thinking outside the box. It's a common saying that carries a variety of meanings, and how literally it's taken largely depends upon the person you're speaking about. It can conjure up thoughts of an ill-conceived idea from a most eccentric individual that's obviously doomed for failure right from the start. You know the type-one that everyone can see will never pan out but plods forward, seemingly spiteful of its pending fate.
Every once in a while, however, we come across a well-thought-out example that involves proven technology, and ultimately provokes the thought, "Why didn't I think of that?" Mark McConville of Birmingham, Alabama, is one of those individuals who thought outside the box and is enjoying his '66 GTO in a completely new manner.
The way Mark's story begins isn't much different than that of other Pontiac hobbyists. "My brother, Jon, owned a '67 LeMans convertible when I was younger, and that car left quite an impression on me," states the 51-year-old owner of a transportation company. "I just loved the look of its stacked headlights and classic body lines. I knew I'd own one someday."
In 1986, he started an airport transportation service that ran between Birmingham and Atlanta, and in 2001, he branched out and began building houses. "I managed to save some money and decided that it was time to buy the musclecar of my dreams. I began looking around at mid-'60s GTOs to get a feel for the market. I heavily researched them to learn as much as I could; in 2004, I purchased a '66 GTO from an Internet website."
A previous owner had performed a body-off restoration, and though the GTO wasn't completely original, Mark felt its tasteful modifications were exactly what he wanted. "It was originally Barrier Blue but had been repainted Montero Red. The black interior was freshly restored, and a 455 resided where its original 389 once did. It had a four-speed transmission and a Safe-T-Track differential with 3.55 gears out back. It was in Portland, Oregon, so I couldn't see it in person, but it looked great in the pictures and seemed like the perfect vehicle for me."
A conventional fuel system...
A conventional fuel system serves no purpose after converting to CNG, so Mark removed the original fuel tank to save weight. These two tanks mounted in the GTO's trunk effectively store CNG, which is pressurized to 3,600 psi. Lincoln Composites produced these particular tanks, which consist of an aluminum shell wrapped by carbon fiber. They weigh just 80 pounds each-nearly half that of a traditional steel tank-and were installed by Phoenix Energy Corporation.
Mark made the purchase and when the GTO arrived in Birmingham, he recalls the day: "I bought it sight-unseen since it was so far way and immediately thought I'd been taken. It ran great and it sounded even better, but I was really disappointed in its appearance. It had sat under a tree and was covered in sap; I thought the paint was ruined. I took it to a local detailer and it cleaned up very nicely. The body was very straight and the paint looked great. I was very happy with the purchase after that."
The motivational force behind Mark's satisfaction was a 469ci fitted with a plethora of goodies from Nunzi's Automotive in Brooklyn, New York. The XY-code '73 455 block was punched 0.060-inch to 4.21, and the journals of its 4.21-inch-stroke, nodular-iron crankshaft had been undersized 0.020 inch and polished. Four-bolt main caps from Nunzi's were added just before the main saddle was align-bored.
Inside the 469 was a set of forged-aluminum pistons with moly rings riding on fully prepared cast-iron Pontiac connecting rods. The pistons were dished enough to create a compression ratio of 10:1 when combined with a pair of No. 64 cylinder heads from a '70 455. The castings were ported and polished by Nunzi's, and fitted with stainless-steel 2.11/1.77-inch intake and exhaust valves, and heavy-duty valvesprings.
At the heart of the valvetrain was a Nunzi's No. 2042 camshaft featuring 232/243 degrees of 0.050-inch duration and 0.460/0.470-inch lift with stock 1.5:1 stamped-steel rocker arms. A Super-Duty oil pump dispensed lubricant from a Nunzi's oil pan and pressurized the hydraulic Rhoads lifters, which were used to bleed off duration at low speed, improving overall driveability.
The GTO received a host of...
The GTO received a host of aftermarket suspension components during the restoration process, including HO-Racing coil springs, a 1.375-inch-front and 0.875-inch-rear sway bar, urethane bushings, KYB shocks, and Lakewood traction bars. A set of 16x8-inch American Racing Torq Thrust wheels with modern GM-licensed GTO center caps and 215/60R16 Bridgestone Ecopia tires keep it in contact with the road.
A '66 Tri-Power intake manifold and trio of two-barrel Rochester carburetors supplied the go power. Ignition duties were handled by a Pro-billet distributor, 6AL box, Blaster 2 coil, and heavy-duty plug wires, all from MSD. A set of four-tube Doug Thorley headers, and 2.5-inch exhaust with a crossover and dual Flowmaster mufflers provided the audible symphony.
"I was so happy with the GTO," says Mark. "I loved the way it looked and sounded. My daughters and I would take it to cruise-ins, and I remember doing a smoky burnout with it in a parking lot after dinner with another couple, but the home market got bad. I lost my job as a builder, and gas was sky high. My wife saw it as an added expense, and I knew then that the GTO was on the endangered species list. I loved it so much, I sold my work truck just to keep it."
The high cost of gasoline was also affecting Mark's transportation company. "Our fuel costs were outrageous," he recollects. "I was going broke trying to keep the fleet running, so I began searching for ways to reduce that portion of it. I knew that many mass-transit systems were using compressed natural gas (CNG) to power their vehicles, so I looked at converting our shuttles to it. It was readily available for public consumption in the Birmingham area at the metro bus station, so we made the switch."
From this angle, what might...
From this angle, what might seem like an ordinary '66 389 Tri-Power engine is actually a well-disguised 469ci engine that features 10:1 compression, ported No. 64 cylinder heads, an aggressive hydraulic flat-tappet camshaft from Nunzi's Automotive, and four-tube Doug Thorley headers. Those aren't Rochester two-barrel carburetors, however. Atop the cast-iron Tri-Power intake manifold are three IMPCO 125 CNG mixers, which act like conventional carburetors, but instead deliver varying amounts of natural gas vapor for normal engine operation in all conditions.
Traveling back to Birmingham from California in the summer of 2009 after purchasing a new CNG-powered van for his transportation company, Mark took the nostalgic Route 66 highway for a portion of the trek. "I was taking in the scenery and had a vision. Why couldn't I make the GTO run on CNG as well? I immediately called my friend Keith Barfield and told him of my idea. As soon as I returned home, we began researching options and found that it was very possible."
According to Mark, no internal engine modifications are required when converting to CNG operation. "Engines that run on CNG tend to have a much longer service life because there's less cylinder wear in the long run," he says. "CNG is a dry gas, all vapor, so there isn't any liquid to wash the oil from the cylinder walls, but that means there isn't any lubricant to protect the valveseats from wear either. Hardened intake and exhaust seats are always recommended when running CNG, but some say it may take 70,000 miles before the effects are seen on a conventional cylinder head."
This high-pressure regulator...
This high-pressure regulator (HPR) reduces CNG pressure from 3,600 psi to 150 as it travels through a vacuum-operated safety-switch toward a low-pressure regulator (LPR). Once past the LPR, it enters a PEV at 5 psi.
Mark and Keith contacted Dave Leivestad at Carburetion & Turbo Systems (CTS) in Shapokee, Minnesota, and explained their plans for Mark's GTO. Dave sent a trio of throttle bodies that fit perfectly onto the Tri-Power intake manifold. "I was able to take the Rochester linkage and install it onto the IMPCO 125 'mixers,'" as they're called in CNG speak. "With a flow capacity rating of 202 cfm and capable of producing 126 horsepower each, the revised Tri-Power setup can deliver more than 600 cfm and generate just over 375 horsepower. That was perfect for the 469."
With the engine modification issues solved, Mark then addressed the GTO's fuel systems. "High-pressure cylinders are required to contain the natural gas and I wanted to maximize travel distance, so I mounted two tanks in the trunk area. CNG is pressurized to 3,600 psi and steel tanks are generally used, but they also weigh around 120 pounds each. Aluminum tanks surrounded by spun carbon-fiber are just as strong and weigh only 80 pounds each."
Mark removed the GTO's original fuel tank to save weight and capped off all of its original fuel lines. He then ran a 1/4-inch stainless-steel line forward from the tanks to a high-pressure regulator (HPR) mounted on the firewall, and added an inline filter and the required shutoff valve for maximum safety. It passes through another series of valves and regulators, and finally reaches the mixers at a pressure of just 0.5 psi.
The GTO's interior features...
The GTO's interior features many replacement components from Ames Performance. The Hurst Comp Plus shifter is connected to a rebuilt close-ratio Muncie four-speed transmission, which features an 11-inch street/strip clutch disc and pressure-plate assembly from South Bend Clutch on one end, and a new driveshaft on the other.
CTS had preset the center mixer, and Mark finely tuned it and the end units for maximum performance. "CNG molecules are much larger than those of typical gasoline, so it doesn't burn as efficiently and typically doesn't provide as much power. It also has an octane rating of 130, so it burns slower too. CNG requires a much hotter spark to initiate ignition, and it generally requires additional spark advance to completely burn." The GTO was already equipped with a complete MSD ignition system, so Mark simply had a CNG mechanic reset its distributor timing curve for optimal performance.
The GTO fired immediately upon initial startup and has run flawlessly on CNG since, states Mark. He admits, however, that he was concerned his Pontiac's wonderful exhaust note would go away, but much to his surprise, he says it sounds better on CNG than it did on gasoline. "The exhaust tone changed slightly, but it sounds like it's more finely tuned than ever before. It's simply music to my ears."
When asked if he's noticed a performance decrease after converting the GTO from gasoline to slightly less efficient CNG, Mark responds, "None that I could really tell. It feels great everywhere. I still love the power rush when the Tri-Power's end mixers open, and it accelerates just as well from a stop." One unexpected benefit he found was startup after it's sat for long periods. "On gasoline, the carburetors would go dry; it took a lot of cranking to fill the float bowls. It fires up immediately with CNG."
The entire CNG conversion cost Mark around $5,000, and measured economy on CNG is roughly 10 mpg-10 gas gallon equivalent (GGE) in alternative-fuel lingo. "Right now gasoline runs about $2.70 per gallon in Birmingham; CNG is $1.36 per gallon. You can see how much of a savings that is. That may not seem like much, but it adds up over time. I don't plan to drive the GTO too often though. I feel driving it sparingly will help me appreciate it more, and I know that it'll cost much less to drive when I do."
Mark says that the GTO has taken on a new life since its conversion to CNG operation.
"I enjoy taking it to conventions and shows, and sharing my experience with other hobbyists. I'm even planning to participate in A Drive To Inspire event this summer, where the GTO will travel 2,200 miles on Route 66, from Santa Monica to Chicago, operating solely on CNG. [The fuel range of the GTO is 140 miles; it will be tailed by a refueling truck housing twin 36-gallon CNG fill-tanks.] I hope to set a world record and show hobbyists around the world that vintage automobiles can operate reliably on CNG."
So what did Mark get for thinking outside the box? The world's first Tri-Power "CNGTO!"
The PEV-series regulator reduces...
The PEV-series regulator reduces incoming CNG from a pressure of 5 psi...
...to just 0.5 psi by the...
...to just 0.5 psi by the time it reaches these flexible hoses, which feed the mixers.
A conventional smog pump,...
A conventional smog pump, added by the previous owner, was plumbed to depressurize the 469's crankcase, improving performance. Though it now effectively evacuates excess CNG vapor from the crankcase, it isn't required when converting to CNG.