BOHZZ: Twin-turbo 400ci Chev powered streeter scores 4th roll racing win

BOHZZ is gearing up for a big week at Drag Challenge 2023

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Turbosmart Outlaw Blown is going to be one hell of a party at this year’s Drag Challenge. At the top of the tree we have two-time event winner Harry Haig in his twin-turbo, big-block HQ Holden and Tasmanian Mark Whitla in his always-competitive Capri. The Capri recently swapped nitrous for a pair of turbos and ran a 7.3-second pass at 193mph in recent testing at HPR.

Alexis Margaritis’s stunning LC Torana is also in the mix, along with Barry Hall in the much-upgraded Rod Shop VL and Andrew Baumgartner’s evil turbo-LS powered HB Torana.

But out of all of them, one of the cars with the most track time and race wins of late is Dave Tierney’s BOHZZ. Powered by a twin-turbo 400ci small-block Chev, Dave’s HZ has been kicking arse at The Bend’s roll racing events, with four event wins and a runner-up spot. Granted, roll racing is a different beast to drag racing proper, but it does show that the HZ is on point.

The car’s current quarter-mile PB is an 8.235 @ 170mph.

That’s not to say 2023 hasn’t been a challenging year for Dave. In fact, he was entered in our 2022/23 Drag Challenge event Jan/Feb, only to have a big off with the car in testing at HPR, munching some panels, the radiator support, some suspension items and parts of the driveline.

“Before it hit the wall, it went 8.2 again and PBd speed at 173mph. Then we added another 5psi next run and came unstuck,” says Dave.

Heartbreaking stuff, but our man got to work on the repairs almost immediately and had the car back on the road in a matter of weeks.

The heart of the matter is a Dart SHP Block, filled with a SCAT 4340 crank, Oliver 6in steel rods and CP pistons. Up top are a set of AFR 220 64cc heads with Manley Extreme intake valves and Inconel exhaust valves. The heads are shaved, and fitted with a .080 cometic head gasket for around 10.5:1 compression. The cam is a custom Comp Cams hydraulic roller, with PAC valve springs. “While the cam is a hydraulic roller, I run it as a tight-lash solid, with BAM DLC lifters. Does the job well!” says Dave.

Externals include a ported Edelbrock Super Victor manifold, modified for 16 Bosch 2200 injectors, with a Wilson billet 4150 elbow and a Plazmaman throttle body. The intercooler is also a Plazmaman unit, with PWM methanol injection for good measure. Turbos are a pair of 7975 Pulsar G42s. Fuel is supplied by a Waterman Mini Bertha mechanical pump.

Taking the punishment is a MV Automatics transbraked Powerglide, a 3.5in moly tailshaft and a braced 9in with a Strange centre, 3.5 gearing and 35 spline axles.

The brains behind all this is a Haltech Nexus R5 VCU with all the fruit including a IC7 dash, CAN keypad, dual NTK wideband, dual fuel and traction control. The whole deal has been screwed together largely by Dave in his shed at home.

Dave has recently started his own business dubbed Pro Wired to serve the motorsport community:

“With 20+ years experience in the heavy industry electrical instrumentation field. Most of that time involved with complex process controls associated with oil & gas, and mining projects at all levels including construction, design, and project management.

“My trade and engineering skills developed over the course of my career to date, combined with my passion for cars and campaigning BOHZZ Racing (mostly all built myself at home in the shed) ultimately led to a vision of starting my own business and the idea of Pro Wired was born.

“Specialising in Haltech, but happy to help and involved with any platform used on your project.”

You can check out the Pro Wired Facebook page here.

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