This story was originally published in the May 2017 issue of Street Machine magazine.
POWER adders are all well and good, but there’s a real science behind extracting every last available horsepower from a stout naturally aspirated package.
What we have here is a GM NASCAR-based combo, originating from Richard Childress Racing in the USA. It’s destined for Shane Woodman’s BMW Sports Sedan, and after a freshen-up and a few tweaks by Bushy at MB Performance Competition Engines, it’s good for 800hp at just shy of the category maximum 7800rpm rev limit. At 356ci in capacity, that’s well beyond 2hp per cubic inch, with nary a turbocharger or nitrous bottle in sight.
“When it came to us it was making 700hp, but we tidied a few things up and played with different camshafts, compression and tuning, and it’s now making right on 800hp from 7500rpm onwards,” Bushy explains. “These things don’t make enormous amounts of torque; they’re designed to rev quickly so you can make your way through the gears fast.”
One obvious change that has been made since this engine was going ’round and ’round in circles Stateside is that the carburettor has been binned in favour of a custom billet eight-throttlebody EFI manifold, with a MoTeC ECU that integrates with all the other MoTeC hardware fitted to Shane’s Beemer. It’s loaded with 1000cc injectors, which are fed 84psi of fuel pressure by no fewer than four Bosch 044 pumps.
The rotating assembly consists of a Bryant crank, Carrillo rods and Gibbs pistons, while the top end retains the GM SB2.2 RCR heads, with T&D rocker gear and Jesel Dog Bone lifters.
The dry sump system has been retained because of the kind of lateral and longitudinal Gs the car will be capable of, and it consists of an Auto Verdi pump and an RCR dry sump set-up.
With a rather lofty compression ratio and an avgas-only diet, it’s no street engine, but if we know one thing about NASCAR donks it’s that they’ll happily withstand sustained high-rpm use. In fact, these sorts of engines make up the bulk of Bushy’s business.
“I’ve been building engines for almost 30 years now, and I specialise in engines for endurance racing,” he says. “That’s how I came to do Shane’s engine, because he wants reliability, and to not have to be constantly pulling it out for a rebuild.”
The brief from Shane to Bushy at MB Performance Competition Engines was to take a proven NASCAR combo and make more power, reliably. Bushy retained the vast majority of the major components, but did plenty of development around camshaft specifications. Needless to say he’s keen to keep the final specs close to his chest. When he was done, he topped the engine off with a custom billet EFI manifold, and tuned the MoTeC on an engine dyno for bang-on 800hp at the crank