1400hp twin-turbo 388ci VH Valiant Charger

Theo Diamond’s Valiant Charger blends old-school carby V8 tech with modern turbo grunt

Photographers: Chris Thorogood

It’s not uncommon these days to see a V8 and twin turbos in a low-eight-second streeter, but the way Theo Diamond’s 1972 VH Valiant Charger takes on that power is anything but normal. You see, the 388ci Mopar R3 mill in the engine bay uses a blow-through carby set-up. There’s no injectors or ECU to be seen – just good old-fashioned screwdriver and jet tuning to go with all that boost.

First published in the February 2024 issue of Street Machine

“It was tempting to start again, as technology evolved during this build, and the goal posts did move several times,” says Theo of his Charger build. “But I made a decision to stay old-school and stuck with minimal electronics. I’ve got a lot of Holley carby tuning experience, and it gives it a point of difference being a blow-through.”

Fifty-four-year-old Theo has owned the Charger since the ripe age of 18; it was his first car. The combo it has now represents the VH’s third major overhaul in that time. “It had a hot 265 with a four-speed that ran 12s in the early 90s, and then a 360 small-block that had it in the 10s in the early 2000s,” he says. “In 2004, we started what was meant to be a quick respray and rebuild, and that took 18 years! This engine was originally meant to be apso, but we found that the second-hand W9 heads weren’t crash-hot, so the decision was made to go twin-turbo.”

The engine and practically the entire car build was done with Theo’s own two hands, which he’s recently expanded into a full-time gig under the Diamond Engines & Automotive name. “I’ve been doing engines and the odd car for years – just a couple a year in my spare time,” he says. “Since COVID, business has got so busy I’ve started doing it full-time, and I’m about to move into a bigger workshop.”

The powerplant Theo built for his Charger uses a Mopar R3 48-degree block, along with a Callies DragonSlayer crank, Carrillo H-beam rods and custom JE pistons. The bumpstick is a Comp Cams solid-roller, and the mill is topped with W9 Mopar heads and a single-plane manifold. A Quick Fuel 750 blow-through carb by RayJE sucks down E85, although Theo does have a second carb tuned for 98 for those longer road trips. In race mode, it’ll spin to 7600rpm and take on around 26psi from the Pulsar Gen 3 3584 turbos – good enough for the car to run a 8.38@167mph PB.

Theo’s never had the engine on the dyno; he street-tuned it from the start. “I’d say it’d make around 1400hp based on the mph,” he says. “The engine can take over 30psi, but because it’s all mechanical, you can’t just push buttons on a laptop when you want more or less power. I’ve had issues with it wheelstanding, but once we get a decent 60-foot, it should go even quicker.”

Completing the driveline is a Reid-case Powerglide built by Neal Racing Transmissions, and a fabricated nine-inch diff knocked up by Sean Mullins. A pair of 325 Mickey Thompson ET Street Rs on 15×10 Weld RT-S spinners hang off the diff when the car’s in street trim, but for the track, Theo uses single-beadlock 15×12 RT-S rollers wrapped in Mickey Thompson Radial Pro 315/60R15s.

Suspension consists of a standard torsion-bar arrangement in the front and QA1 coil-overs in the rear, and the steering has been converted to more modern rack-and-pinion with an Elko kit.

“It drives really nice on the street; we do a lot of cruising with it,” says Theo. “I’ve dialled the carby so it starts and drives like an injected car, but that takes a lot of time tuning the cruising mixtures – they’re just as important as the racing set-up.”

Given the Charger’s strong street credentials, we politely hinted to Theo that he’s in a prime position to take on events like our own Street Machine Drag Challenge. “I’ve definitely thought about it, but I just haven’t fully committed to going through with it yet,” he says. “I’ve seen what those entrants go through, and it’s bloody full-on! So we’ll see.”

We hope he caves and brings it along for a week of drag-and-drive goodness, but in the meantime, it’s likely you’ll see the Charger either on the streets of Melbourne or belting down Heathcote Park Raceway’s strip. “I’m keen to get it back [to Heathcote] and get it quicker,” Theo declares. “I always enjoy racing this thing.”


Paint:Ford Bionic Blue
Brand:388ci Mopar R3 48-degree
Induction:Mopar single-plane
Carby:RayJE Quick Fuel 750 blow-through
Turbos:Pulsar Gen 3 3584
Heads:Mopar W9
Camshaft:Comp Cams solid-roller
Conrods:Carrillo H-beam
Pistons:JE custom
Crank:Callies DragonSlayer
Oil pump:Melling HV
Fuel system:Bosch 044 pumps
Cooling:Aussie Desert Cooler radiator
Exhaust:Twin 3.5in
Gearbox:Neal Racing Transmissions Powerglide
Converter:ProTorque 3500rpm
Diff:9in, 35-spline, 3.9:1 gearing
Front:Torsion bar, QA1 double-adjustable shocks
Rear:Four-link, QA1 coil-overs
Brakes:Wilwood discs (f), ED Falcon discs (r)
Master cylinder:Wilwood
Rims:Weld RT-S; 15×5 (f), 15×10 (r)
Rubber:Mickey Thompson Sportsman 26×7.50R15 (f), Mickey Thompson ET Street R 325/50R15 (r)

John Sinosich for his valued opinion and skills; Paul Harpham, Simon Grig, Claude Sinosich and Harry Genovezos, who have all contributed during the build and on race days; my wife Mary and daughters Tiffany, Anastasia and Ella for their support.