Harrop-supercharged 403ci LS – Mill of the Month

These days, it’s not uncommon to come across regular streeters with four-digit power levels, and a boosted LS motor is a popular way to join that club


THEY might be decried as boring by some, but an LS can make great power with good reliability and easy maintenance schedules, as this latest Harrop-supercharged iron block from Sydney’s Warspeed Industries proves.

Using mostly off-the-shelf parts, this build should make 1000hp reliably, thanks in part to the intercooled Harrop TVS2650 pump sat on top. Starting with a 6.0-litre Gen III LQ4 that had been dragged out of a South Carolina river, Warspeed’s Troy Worsley had Jenkins Performance Engines in Penrith machine the block and balance the bottom end, after it was hot-tanked multiple times.

“Even though this is a balanced assembly from Texas Speed and a nice kit, I always double-check to within a very fine spec just to be sure,” Troy says. “I’m happy for customers to come back and have a beer once I’ve done their engine, but I don’t want to see them come back with problems!”

The core of the combo is a forged Texas Speed crank and H-beam rods, along with 68cc, 10.67:1-comp Wiseco pistons for a total span of 403ci. The cam is a Texas Speed hydraulic-roller, custom-ordered at 223/245 degrees with .629in-lift on a 116-degree LSA to promote good chamber-filling characteristics for the air being pushed into the Precision Race Components LS3 heads. The CNC-ported 260cc castings, also sourced from the fellas in Texas, have been fitted with custom Manton pushrods working between the Johnson short-travel tie-bar lifters and Texas Speed’s 1.72-ratio rocker arms.

The front of the motor features many smaller upgrades, like a Rollmaster dual-row timing chain and Gen IV cover, Melling oil pump, Warspeed oil pick-up brace and MMS timing pointer kit. The Harrop 8PK billet LSA drive bracket ensures the 18 per cent overdriven TVS2650 blower doesn’t suffer belt slip, while the integrated Harrop 100mm drive-by-wire throttlebody on the front of the water-to-air intercooled supercharger is ready to swallow bulk atmosphere.

Raceworks 1500cc injectors and –8AN fittings supply the corn juice to the donk, with a Turbosmart fuel pressure regulator monitoring flow. Ignition is handled by stock LS3 coils on Tuff Mounts relocation brackets, while a custom four-port steam kit prevents hotspots in the heads. Custom rocker covers from Shaun’s Custom Alloy provide some bling. Scotty Barter from Oxytech Powder Coatings powdercoated the accessories, including the Moroso sump, GM water pump and all the brackets and idlers.

“This should be a great street combo that will make around 1000hp at the crank,” Troy says. “The compression will make it nice and snappy on E85, but it will cruise really nicely with the electronic throttle. The customer is going to run a Haltech ECU with it, and it will be paired up to a Hughes 4L80E, so it should be great on the highway.”


THE beauty of the early 6.0L LS engines is that you can fit the deep-breathing LS3 heads to them without bore shading issues. With a 58-tooth reluctor wheel on the Texas Speed crank, this LQ4 has also been updated to run Gen IV LSA drive belts, sensors and accessories, making it a cinch to maintain.

Warspeed Industries,