1969 Plymouth Road Runner with 498 HEMI
Posted: Tue Aug 23, 2016 10:09 pm
Dave Dudek’s 840HP, 498CI 1969 Plymouth Road Runner
http://www.hotrod.com/articles/dave-dud ... ad-runner/
I cannot imagine trying to put down that much power through that little rubber!“I just love the sleeper concept,” said Dave Dudek, owner, builder, and pilot of a 1969 Plymouth Road Runner that runs low-10s and more than 130 mph in a car that looks like it belongs in an ISCA-judged car show. For those unfamiliar, Dudek competes in a series dubbed Factory Appearing Stock Tire (FAST), and its mantra is self-explanatory of its rules. The 4,000-pound muscle car has produced a best of 10.14 at 138 mph on original-type Firestone tires.
The outward appearance is limited to stock, but what lurks beneath is a sinister, high-tech engine combination that has been refined over the years. The Hemi engine displaces 498 ci while churning out 840 hp on the engine dyno. Dudek worked in conjunction with Best Machine Racing to create this beast as it buzzes to 8,200 rpm, and he hopes to put the Road Runner into the 9s when the weather cools off. It isn’t his first go around with this type of build, as he has been involved in FAST racing since 2000 and this is his fourth car for the series.
Making horsepower is one thing, but getting it to the ground on a set of vintage tires is a completely different story. The trick is a mix of driving style coupled with simple ignition techniques and a set of balding tires. “I have tried it all,” mused Dudek as he walked us through his world. The Michigan-based racer first suggestion to go fast is driving style and said, “You can’t lay into the gas off the line. The best way to describe it is like putting an egg on top of the pedal and step on it, trying to push the pedal down without breaking the egg.”
Once you get the technique down, the two other tricks he shared are weights in the distributor for the proper ignition-timing curve and a set of balding poly-glass tires. If you are looking to read about an exotic ignition control box, don’t waste your time. According to Dudek, he has tried it all from a few traction-control systems, including one from Davis, and an MSD digital-ignition system. He has come full circle, and a finely tuned distributor from Rev-N-Nator works perfectly, with 1.52 60-foot times as proof.
Dudek relies on a set of Firestone G70-15 tires for his Road Runner, hardly a set of high-performance rubber. “Once they start to going bald, they start hooking,” he proudly explained. When you run the category for as long as Dudek, you tend to try tricks and start investing in odd ways to gain traction. He revealed, “I tried it all, from spray bars in the wheelwells with VHT to a junior chemistry set in my kitchen to soak the tires. I even got tire-softeners from Europe.” None of it worked and simply wearing down a pair of tires seemed to do the trick, saving time and money in the long run.
As the weather cools off, Dudek is chomping at the bit to get out to the East Coast to take a shot at the single digits, making it one of the most unassuming muscle cars we’ve ever seen.
The factory Hemi block was increased to 498 ci by way of a 4.250-inch-stroke Molnar crankshaft and a 0.070-inch overbore, putting the final bore size at 4.320 inches. The bores are filled with Diamond custom pistons and compression ratio is placed at 14:1. The GRP aluminum rods are 7.100 inches long to connect the pistons to the crankshaft. The oiling system is a highly modified setup that looks factory from outside due to the class rules. A Miloden oil pump delivers the oil and Dudek modified the block with a more efficient oil-return system that includes larger orifices. It keeps the big engine well lubricated as it spins to 8,200 rpm.
The valvetrain is a race-bred setup that is centered on an LSM solid roller camshaft. Dudek wasn’t afraid to share the details, unlike many other hardcore racers. The stick features 0.799-inch lift on both the intake and exhaust while duration is 253/262 degrees at 0.050-inch lift. The lobe separation is kind of wide at 114 degrees. The cylinder heads are, of course, factory 559-M Hemi heads, but Modern Cylinder Head put them through an extensive exercise in its porting room. A set of Xceldyne valves were installed—2.25-inch titanium intake valves and 1.94 stainless-steel exhaust valves. Final flow numbers are 410 cfm for the intake ports and 313 cfm for the exhaust (both measurements were taken at 0.800-inch lift and using 28 inches of water). Ray Barton 1.7:1 roller rocker arms are bolted to the cylinder heads.
A factory cast-iron intake with two inline four-barrel carburetors is heavily modified. The carburetors were sent to Dale Cubic where each was CNC-ported and now have custom internal components. Cubic brought flow from 625 cfm up to 1,000 cfm and the carbs provide a crisp throttle response and excellent idle qualities. Modern Cylinder Head, using Dudek’s specific design, handled the intake porting. One trick that is hidden is the use of a Star electric-driven vacuum pump, which Dudeck mounted in the trunk.
The fuel system is straightforward, with a 4-gallon cell mounted in the trunk with a pair of Holley 160-lph fuel pumps feeding the carburetors. The Road Runner has larger fuel lines, which is legal, but Dudek mentioned that one of his previous FAST race cars ran 9s with the stock 5/16-inch fuel line. The 840hp Hemi engine runs on VP Racing Fuels Q16 gasoline. The ignition system is very basic with Firecore spark-plug wires and a Rev-N-Nator distributor as the two most noteworthy components.
One of the more odd requirements is the use of factory exhaust manifolds, which aren’t known for stellar performances, but Dudek has a tried-and-true technique to make them perform. He bolts on a steel cover to the flange area and then drops the manifolds in a bucket of acid. The manifolds are submerged in the bucket for a few days, depending on the weather, and they emerge 5 pounds lighter. Depending on the engine combination, Dudek will then have the manifolds extrude hone-ported.
Like the engine, a factory transmission is required and that means a 727 Torque Flite is in service. Godfather Racing is responsible for building the bulletproof transmission. A PTC 9.5-inch torque converter with a 3,400-rpm stall speed sits behind the stroker engine. Dudek spent a considerable amount of time testing different converters before settling on the PTC unit. He said the converter is a crucial component to control the wheel speed due to the severe tire limitations.