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BUBBA’S 370CI TWIN-TURBO HOLDEN V8

By Scott Taylor | Photos: Nathan Jacobs, 09 Apr 2017 Features

VH Commodore twin turbo Bubba wide

We explore the whys, wherefores and hidden depths of Bubba’s Drag Challenge-winning Holden V8

JUST like the lion is king of the jungle, Holden’s V8 was king of the Aussie streets back in the 80s and 90s. Even into the early 2000s some of the highest-horsepower street cars in Australia were Holden-powered. Remember the heyday of the Summernats Horsepower Heroes competition? Eddy Tassone, Brett Waine and Rob Vickery all made over 1000hp at the treads using factory Holden blocks.

Unfortunately since the introduction of the all-alloy LS1, and the veritable parade of Gen III/IV engines that followed, the demand for the locally made V8 has waned.

It’s not totally out of the picture just yet however, and if guys like Bubba Medlyn, Glenn Wells and Craig Bennett have anything to do with it, we’ll be seeing kick-arse Holden V8s for a few more years yet. So let’s talk to the main players behind this 1600hp monster, and have a look at what goes into building it.

CRAIG BENNETT

“I LOVE the Holden V8,” Craig says. “The firing order, the valve angle, and the shallow combustion chamber are all better than the LS.”

All those factors help the Holden V8 punch way above its weight, but Holden stopped making engine blocks over 15 years ago and good cores are getting harder to find, which prompted Craig to start casting his own. With priority mains oiling, siamesed bores, four-bolt mains on all five main caps and an extra-thick deck, there’s a lot to like about the Little Paw block.

“It’s stronger than your generic Dart block,” Craig says, “and I can deliver it exactly how the customer wants it. Bigger lifters, bigger bores, roller-cam bearings are all available for the same price. It fixes all the problems of the original; you can’t fix the deck thickness, bore thickness or oil issues in the factory block.”

BUBBA MEDLYN

“IT’S DEFINITELY not cheap, but I like to be different,” Bubba says of his decision to stick with the Holden bent-eight. “Swapping in an LS is the cheap way to go, or so everyone reckons. At this level though everything is custom and that gets expensive no matter what you’re building. I probably could have built an LS combo that would make the same power for three-quarters of the cost, but then I’d just have another LS.”

Despite the cost involved, Bubba is a fan of the Torque Power block, and they’re pumping some serious grunt out of his 370ci combo.

“We’re putting at least 1500hp through that block. It’s not cheap but it’s worth it. When you’re not breaking parts then it’s not a lot of money,” Bubba says.

On the chassis dyno the VH made over 1350hp at the treads, and the big fella reckons there’s more to be had if he wants to free a few more moths from the wallet.

“The block the capability to take six-bolt heads, but I already had Yella Terra –9 heads from the old combo, so I kept them,” Bubba says. “Also the Torque Power intake I have is one of Craig’s first designs; we’d probably make another 120hp with one of his new intakes.”

Of course good components are one thing; having the right people around you is another. Bubba tapped Glenn Wells Racing to handle the build, and why wouldn’t he? Glenn builds some of the toughest engines in the country.

GLENN WELLS

“IT’S a basic thing,” Glenn says. “It’s just got good-quality components. To be honest I tried to talk Bubba out of building a Holden a hundred times, but he’s a stubborn bastard!”

The saving grace in Glenn’s eyes is the Torque Power block. “If we didn’t have that we’d be stuffed,” he reckons. “Its strength and its size help keep it alive. The problem with the standard Holden V8 is that it’s weak and it’s got a terrible oil system. The Little Paw block fixes all that. I’ve never met anyone who is as hard on engines as Bubba; he used to split the factory blocks through the Welch plugs. We spent a lot of time on factory blocks, constantly chasing our tails.”

Inside it’s all good gear. The crank is a COME Racing billet item with a 3.48in stroke like you would use for a tough 355-cuber. Combined with a bore size of 4.155in, this yields a displacement of a little bit over 370 cubes. There’s a set of Carrillo rods and custom-order forged pistons with a static compression ratio of 9:1. Glenn has John Sidney Racing do all of his machining and the block has been fire-ringed to seal in the goodness.

The raised cam tunnel has created some interesting issues. The custom mechanical roller cam runs in 50mm roller bearings, and Glenn is keen to keep the lift and duration of the bumpstick to himself. But lifting the cam within the block changes the pushrod angles, and a whole bunch of clearancing had to be done to the pushrod holes in the Yella Terra heads. Because everything is so tight they’ve had to stick with 5/16in pushrods, so they’ve gone with some extra-heavy-duty 110thou-wall-thickness pushrods.

“Craig has addressed this issue with his own Torque Power heads,” Glenn says, “so we’ll probably take a good look at some of his heads as an upgrade in the future.”

EXTERNALS

HAVING a solid core is vital to making good horsepower, but the external gear is just as important with an engine that eats up boost like a fat kid swallowing M&Ms. At the moment Bubba’s engine runs a pair of Garrett GTW billet 67mm turbos that are already proving to be too small. They found the new combination was developing so much back pressure that they had to pump 60psi of CO2 pressure into the 60mm Turbosmart wastegates through the AMS-2000, just to get 29psi boost on the track.

Fuel and spark is controlled by the Haltech Elite 2500 ECU tuned by Jason at Tunnel Vision, with an MSD crank trigger keeping an accurate timing count and ID2000 injectors flowing as much E85 as the beast can handle.

Despite the fact that the combo is relatively small in displacement, has the wrong turbos and uses the much-maligned Holden motor as its basis, the bloody thing just works. Over 1350rwhp is a lot in anyone’s language and it was great to see the old Holden getting the win while surrounded by LS engines. Holden stopped building these cast-iron dinosaurs a long time ago, but they’re still here and kicking arse, so it’s fitting to say: the king is dead; long live the king.

 

The guys switched from Turbonectics 76mm turbos to Garrett 67mm turbos this year, but it looks like they’ve already hit the wall in terms of performance. Bubba reckons they’re already looking at options

They broke the mandrel running through the balancer and lost the MSD crank trigger at Swan Hill, but the guys left the old VT Commodore dizzy in the back. “That came in very handy,” Bubba admits. “We got it back to Melbourne using the dizzy and fixed the crank trigger when we got back”

The turbo headers were built by Tunnel Vision Turbocharging, while Brett at All Race built the stainless turbo dump pipes. In this shot you can also see the six-bolt head capabilities of the Torque Power block, which aren’t being used by the Yella Terra heads

Up top there’s an old Torque Power intake with a Wilson 105mm throttlebody and ID2000 injectors. The throttlebody pokes towards the rear to receive the chilled boost from the custom water-to-air intercooler set-up

Rather than trusting the factory-style oil pump, the guys have gone with a single-stage, belt-driven Peterson pump to handle the oil flow. The sump is an ASR unit that the boys at All Race have customised to suit Bubba’s engine

EGT (exhaust gas temperature) bungs have been fitted to the primary pipes of the turbo headers. Bubba reckons that EGTs are vital for a proper tune-up. “They’re a lifesaver,” he says. “Good tuners always use them”