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Rob Matheis’ 1,200 HP, Twin-Turbo Hemi ’65 Mustang Street Machine

By Andrew Wolf June 26, 2019


Rob Matheis’ many crafty creations have graced the digital pages of Dragzine in the past, and with his family-owned chassis shop in Missouri back in full swing, he’s got another piece of artwork to show off the world.

This 1965 Ford Mustang, begun six years initially as a project for his son, Nick, was completed this month and is primed to put in some time on the roads in and around Matheis’ House Springs, Missouri home.

“I was building it for my son. As we got going on it, things got a little crazy for it to be his first street car, and so he decided go with something different, a 2006 GTO, and so I bought this car off him,” Rob shares.

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The Mustang, all factory steel with the exception of the hood and front valiance, rests upon a full 25.5/25.1-spec tube chassis. Weighing in just over 2,900-pounds with Matheis in the seat, it features high-end tricks from front to rear, including a full carbon-fiber interior to keep weight to a minimum.

Such a sleek car would’t be complete without power to match; for that, Matheis assembled a circa-1957 354 Chrysler Hemi and mated it with pair of 66mm Precision turbochargers. Modern internals and cylinder heads were utilized in the original Mopar Hemi block, but it nevertheless pegs the cool-o-meter.



“I have a buddy that does nothing but early-model Hemi’s, and he was out here while we were working on his car and I said one day, ‘one of your Hemi’s would look pretty cool in here.’ The next day he showed up with a short block and said, ‘here, you can have it.’ Once we got it all put together, it was definitely the most expensive free motor I’ve ever had,” Rob says.



The Hemi is bored .040-inches over and outfitted with an aftermarket steel crank, H-beam rods, and 9.5:1 compression Ross pistons. HotHeads aluminum heads top the block, and Matheis custom-fabricated the intake manifold and used old Hooker side pipe cover to create a trick upper plenum. A Holley HP ECU and ignition system provide the spark and fueling commands to 150-lb/hr injectors. Custom side-pipes route the exhaust gases out just fore of the rear wheels for a truly street look.

“With the turbos, it’s very quiet; I have a ’70 Camaro with an LS and single-chamber mufflers on it and it’s quieter than that car,” Matheis notes.

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The turbochargers are positioned near the firewall aft of the front wheels and draw air through the cowl; the intake manifold bends downward and merges into a single inlet, where the throttle body is positioned down low below crankshaft-level. The intercooler is located in front of the radiator, and the blow-off valve can be seen protruding from the grille, giving a slight hint at what’s under the hood.

A manual valve body Turbo 400 is paired with a 4,500 RPM-stall converter to send the power back to a Strange Ultra case housed inside a custom 9-inch rearend with 3.90 gears and 40-spline axles. The housing hangs from Matheis’ Pro Mod-style, chromoly four-link with a wishbone and anti-roll bar. Strange coilovers provide the dampening the rear, while Strange Alumastruts are located up front. American Racing wheels front and rear in black finish set off the exterior with a contrasting look to its white color.

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The factory ’65 dash was customized to fit the Holley HP dash in the center and a Dakota Digital analog dash in the factory location, with the entire assembly moved back 4-inches closer to the driver’s seat.

A glass front windshield is paired with lexan windows both side and rear — the lexan door windows also roll up in factory fashion.

Matheis’ machine is a certifiable street car, making its first public appearance last weekend at the Street Machine Nationals in DuQuoin, Illinois.



“We put the first tank gas in it there,” Rob notes. “We just went on Saturday, and later in the afternoon when the rain stopped we cruised it around the fairgrounds and took it out and cruised it on the street the rest of the day.”

Matheis adds, “we’ll race it some. It’ll probably be a while…while it looks brand new I’ll probably take it a few shows and do that kind of stuff with it, but next year we’ll probably start racing it.”

With an estimated 1,200 horsepower on tap, Matheis conservatively expects it to run in the low eights, but won’t discount dipping into the high-sevens.