They might be best known for building big-inch combos that tower above bonnet lines, but the team at Sydney’s ProFlo Performance will happily work to extract maximum power from a given engine no matter what it looks like. This 7.0-litre LS is a case in point.

First published in the December 2024 issue of Street Machine

“At the end of the day, the big blown stuff gets noticed more, but these Harrop combos are great, as they make plenty of power and you end up with a more street-legal car,” says ProFlo head honcho Paul Sant. “This is going into an HJ Holden show car, which will become a streeter and may get raced a bit later on. The customer wanted 1000rwhp, and this combo has done 1225hp and 920lb-ft on the engine dyno, running E85 and around 18psi boost.”

Built around a Dart block, the LS-based combo swings 427 cubes thanks to a Callies Magnum crank and Ultra rods, with Diamond pistons squeezing a street-friendly 10:1 comp. Paul specced out a custom-grind hydraulic-roller bumpstick from Bullet for easy maintenance, while a pair of Mast Motorsports Black Label six-bolt cylinder heads were fitted with Texas Speed rockers and screwed down on ARP hardware.

“LS engines are just an amazing platform to build power,” Paul says. “This engine uses a Dart block, but we still play with factory blocks; they just have their limitations on cubic inches and strength.”

Cylinder pressure is one area where factory blocks of any kind get stretched beyond the OE engineers’ nightmares, and this particular mill cops a lot more atmosphere than GM ever intended for the LS. The additional ozones come courtesy of the filthy great Harrop TVS2650 intercooled supercharger that sits proudly between the rocker covers.

Since the ProFlo team is pushing nearly 20psi through the top-mounted party-starter, they’ve wisely opted for the 8PK Harrop billet tensioner. An integrated, 110mm drive-by-wire Harrop throttlebody also provides an extra 20mm of diameter over a stock GM 90mm unit, which suits deep-breathing combos like this one to a T.

ProFlo also ported the 2650 blower to increase the unit’s lung capacity, allowing even more sauce into the LS. “We got it ported just to make sure we definitely hit the customer’s request for 1000rwhp,” Paul says. “But whether they’re ported or not, the instant torque you get from these blowers is just awesome.”
While we’re used to seeing max-effort combos rocking dry-sump hardware, this 427 retains a traditional wet sump – a gated Moroso item that offers far better oil control than the stock pan. Similarly, the TH400 that will be coupled to the blown bent-eight can handle everything the combo can throw at it.
Fuel is provided by 1600cc injectors, and a Haltech Nexus VCU controls the whole shebang, including flex-fuel capability so the LS can run on E85 when it’s party time and 98 premium unleaded when calm cruising is the order of the day.

Whichever fuel the owner chooses to stick in their HJ, we’re sure this spicy late-model small-block will keep them well entertained.

ProFlo Performance
Campbelltown, NSW