427-cube Whipple-blown Windsor – Mill of the Month

This Westend Performance-built 427ci Windsor is destined for a customer's Ford Capri street car


What a golden age of horsepower we’re currently enjoying! Take this Westend Performance-built 427ci Windsor, for example: it makes 1170hp at the crank and 950 at the tyres. That sort of grunt used to require a laundry list of custom-engineered components, but today it can be achieved with off-the-shelf parts and pump fuel!

This article was first published in the March 2020 issue of Street Machine

“There isn’t anything exotic in this motor,” says Westend Performance bossman Sam Fenech. “My customer told me he wanted a blown small-block Ford for his Capri street car, then gave me complete freedom to build it however I wanted. That is pretty rare to be able to have complete creative control over a build, so it was really cool.”

It kicked off with an aftermarket Dart block stuffed with a Callies crank and Callies rods, 9.5:1-compression JE pistons and a mechanical roller cam. Sitting on top of the 427ci bottom end are a pair of AFR 225cc heads housing T&D rockers and upgraded valve springs. A Holley HP ECU controls the show.

“Because Windsors are difficult to find good manifolds for, we bought a Holley Hi-Ram for a 351 Windsor and modified it,” Sam explains. “This gave us 16 injectors: eight Siemens 80lb injectors above the blower and another eight 80lb injectors in the ports. We used twin fuel pressure regulators on the dyno, so we boost-referenced the eight injectors below the blower.”

That blower is one serious pump: a Whipple 510R twin-screw pushing 16psi into the seven-litre small-block. Sam reckons there is more in it, especially with the pump E85 fuel being so boost-friendly.

“If someone says they want 1000hp, I tell them to go Whipple,” says Sam. “You can drive a Whipple on the street and not have the intake air temp issues you get with a traditional Roots blower. You don’t have to spin a Whipple as hard, and they say it’s the equivalent of a 14/71 but physically the size of an 8/71. If an 8/71 makes 800hp on pump fuel, a Whipple will make 1000hp. If you keep pushing them, the Whipple will make more power.”

The Windsor isn’t all about brute force though; it is a seriously good-looking bit of kit thanks to liberal black powdercoating, including the first pair of Windsor valve covers that Shaun’s Custom Alloy has made.

“A couple of cool points on this motor include the EFI and the Smart Coil kit, which uses coil-on-plug technology like a new car,” says Sam. “For the crank trigger, we fitted a Holley hall-effect sensor kit and used a cam position sensor in place of the distributor.

“We spun it up to 7000rpm and it was heading for the sky,” Sam laughs. “We took it to 6500rpm on the hub dyno and the customer said, ‘That’s enough!’ He didn’t know how he was going to use that much power anyway.”


“Because the engine was going into a Capri, we couldn’t get an oil pan from the USA, so we used a more stock-style one,” Sam says. “We used all of the off-the-shelf parts in this build; there isn’t anything crazy in terms of custom-made parts.”

Westend Performance,
Campbelltown, NSW