On Gas or Alcohol, This is One Flyin’ Flathead!

ROANOKE, Virginia’s “Flathead Charlie” Overfelt and his wife Liz have campaigned this Altered 4.71 GMC with a supercharged 276-ci Mercury 8CM engine in the drag racing nostalgia class for several years. They’ve also won their fair share of events, including the Goodguys Rod & Custom Association drag racing series (five wins 1991-96), ATCO Flathead Nationals (winner 1998), Oldies but Goodies Flathead Nationals (winner 1998) and Bowling Green NHRA Hot Rod Reunion (winner 2006-07); the team was also a co-winner in class at the 2011 Texas State Championships.

Built entirely at the family business, Roanoke’s Overfelt & Son Welding, by Charlie and his son Christopher, the low-slung “T” features a 105-inch wheelbase and a double rail solid suspension altered chassis fashioned from 4130 chrome-moly tubing. However, it’s the drivetrain powering this 1,450-pound missile that really turns heads.

Charlie’s roadster features a set of Overfelt-machined billet aluminum cylinder heads (secured with ARP head studs) that cap off a healthy Mountain Land Machine Shop-prepared 1953 Mercury 8CM block. That same block is stuffed with a Harmon’s-Machine- prepared 1953 Mercury flathead crank, reworked 1953 Mercury flathead connecting rods, Total Seal-equipped 9.5:1-compression Wiseco pistons and an Isky camshaft. The bottom end features a Rotella oil-filled OE 5-quart Mercury windage tray oil pan wrapped in an STT safety blanket. What’s most interesting about this vintage powerhouse is its GMC 4.71-based Flex Fuel induction system.

“At certain events where we don’t need to run that fast, we pull the Hilborn two-hole injectors and alcohol off and run the 1150 Holley Dominator with gas to slow the car down,” Charlie says. “For example, when we went to New Hampshire for the 2015 New England Hot Rod Reunion, I took a full second out of the car and was still #1 qualifier in the inline/Flathead class at 10.73. Then whenever I want to go faster, I just put the alcohol and injectors back on.” At this writing, a 9.70-140 clocking (on alcohol) and a 10.73-124 (on gas) are the roadster’s optimum performance numbers.

Another unique feature of the Overfelt Altered is its TH 350 automatic transmission. Charlie machined the transmission adapter to accommodate the GM TH 350 bell housing. The TH 350 was built by Fleet Pride Transmissions, is maintained by Cecil Ferguson and activated by a Hurst Quarter Stick. The tranny also features a 14-inch Chevrolet flex plate, an 8-inch 4,000-stall-speed A-1 torque convertor and a 302 Ford starter. The final link in the car’s powertrain is an Overfelt-and-Son-fabricated 12-inch driveshaft that sends the power back to a narrowed 4.11:1 Richmond and Strange Engineering-equipped Ford 9-inch rearend. Tucked in the turtle deck are the Exide battery and hand-built radiator with ½-inch aluminum tubing and an electric fan. The latter equips the driver for making long burnouts and dry hops in addition to allowing plenty of time to back-up and stage the car without burning up the engine.

“The car leaves the line at 3,200 rpm,” Charlie says. “In all the years I’ve been running this combination I’ve never hurt the main webs. Sure, I’ve hurt the crank a couple of times. After all, those 63- year-old Mercury 8CM cranks can only take so much abuse!”

We’re hoping that this is going to make us one of the quickest and fastest Flathead cars in the eliminator. Right now Minnesotan Rick Schnell holds the record at 7.64-175.00 on 80% nitro. Now that’s cooking! //—Charlie Overfelt

EPILOGUE

As if the current performance figures for Charlie’s Flathead weren’t impressive enough, he informed us that he’s currently working on a new Enderle-equipped port injection system using C&C Automotive parts with Jeff Robinson tuning.

“We’re hoping that this is going to make us one of the quickest and fastest Flathead cars in the eliminator. Right now Minnesotan Rick Schnell holds the record at 7.64-175.00 on 80% nitro. Now that’s cooking! However, I would be happy to run in the mid-eights on alcohol [requiring the use of an STT Equipment parachute], which would certainly be more than quick enough for me.”

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TECHSHEET

CHASSIS: NHRA-certified 105-inch wheelbase double rail chrome-moly construction by Overfelt & Son Welding, Roanoke, VA. Bottom rail 1 ½ inches, top rail 1 ¼ inches, featuring a motor plate, a mid plate and transmission mount

SUSPENSION: Solid mountfrontandrear

REAREND: Narrowed Ford 9-inch (40 inches) equipped with a 4.11:1 gear Richmondspool, Strange Engineering 31-spline axles and 11×2-½-inch Ford truck drumbrakes

FRONTEND: Solid-mounted and chrome-plated 1⁄5–inch- diameter .025-wall dropped tube front axle equippedwith SPspindles

STEERING: P&Sdragster type

FRONTWHEELS: 18-inch American Racing spindle-mount altered wheels

FRONTTIRES: Treadless 18-inch Goodyear Eagle

REARWHEELS: 12-inch Rod Lite

REARTIRES: M/TETDrag 13×15 inches

BODY: A&IFiberglass 23-T competition roadster body modified by the owner to include a tachometer bubble on the cowl and recessed single 1939 Ford teardrop taillight to meet NHRArequirements

PAINT: By Charlie Overfelt, Candy Apple brand Candy Blue metal flake with Yellow, Redand Green flames

INTERIOR: Overfelt aluminumpaneling and flamed seat upholstered by Wade& Son Upholstery, P&Sbutterfly steering wheel, five-point Race Quip safety harnesses and 10,000-rpm Auto Meter Pro Comptachometer

ENGINE: 1953 Mercury 8CM flathead by Mountain Land Machine

CRANK: 4-inch 1953 Mercury by Harmon’s Machine Shop

CONNECTINGRODS: 7-inch Mercury Flathead

PISTONS: 9.5:1-compression Wisecowith Total Seal piston rings

CAMSHAFT: Isky

VALVES: 1 ½-inch Manley intake, 1 5⁄8-inch Manley exhaust

OILPAN: OEwindage tray, 1953 Mercury 5-quart oil pan filled with Rotella 15W-40 oil and protected by an STT safety blanket

CYLINDERHEADS: Overfelt-machined 1.25-inch billet aluminum

SPARKPLUGS: Long Reach NGK-8

SPARKPLUGWIRES: Taylor

MAGNETO: Tom Cirello with MSDTransformer

HEADERS: 1 7⁄8 inches by Overfelt & Son Welding

INTAKEMANIFOLD: Manufactured in Australia by Mitchell andmodified by Charlie Overfelt

SUPERCHARGER: 1:1 drive GMC 4.71

PULLEYS& BRACKETS: Overfelt & Son Welding

INJECTOR: Two-hole Hilborn with four nozzles (alcohol)

CARBURETOR: Holley 1150 Dominator (gasoline) equippedwith #95 jets front and rear

TRANSMISSION: GMTH 350 by Fleet Pride Transmissions (Roanoke, VA) andmaintainedby Cecil Ferguson

FLEXPLATE: Small-block 156-tooth Chevrolet 14 inches in diameter

TORQUECONVERTOR: 8-inch-diameter 4,000-stall- speed A-1

SHIFTER: Hurst Quarter Stick

STARTER: 302 Ford

DRIVESHAFT: Overfelt and Son 12 inches

FASTENERS: ARP

FUELTANK: Moon 5-gallon with Moonhandpump

ENGINECOOLING: ½-inch tube aluminumradiator and electric fan located underneath the turtle deck

BATTERY: Exide, samelocation as radiator

WEIGHT: 1,450 poundsminusdriver

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