Jon Kaase Racing Engines’ 598ci big-block Ford – Mill of the Month

In discussions of ground-pounding FoMoCo engines, one name always comes up: Jon Kaase.

Photographers: Ben Hosking

The Georgia, USA-based engine builder has taken more Engine Masters wins than most of us have had hot dinners, and he was the number-one choice for Hunter Valley resident Chris Lewis when he went shopping for a new donk.

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

“My car is a ’74-model XB Fairmont GS coupe, which was originally white with a 302ci,” says Chris. “I didn’t have the original motor, so I started wondering what I could fit in there. I didn’t want solid lifters or a really revvy race-style motor, or anything that was going to need a lot of maintenance. I’ve followed Jon Kaase for a while and I had the cash there for one of his engines, so I decided to pull the trigger.”

What Chris ordered is a seriously wild piece of kit, polished front to back and top to bottom and making 1000 naturally aspirated, pump gas-chugging, electronically port-injected ponies. It is based around an iron A460 Ford Motorsport block, which Chris had specced to his individual requirements.

“Jon asked me heaps of questions about exactly how I wanted my motor,” he says. “It is a crate motor, but it’s essentially custom-made, as I wanted it built to go into a car that is a real street driver, and I’m putting a Tremec T56 Magnum six-speed manual behind it. This meant Kaase had to change some of the specs to suit, like opting for a hydraulic-roller cam.”

Inside the 10.30in deck-height Ford Motorsport block is a 4.5in-stroke forged 4340 Scat crank, Scat 6.7in H-beam rods and Diamond 4.6in-bore pistons pushing 11:1 compression. A custom-grind Comp hydraulic-roller cam works on Kaase’s own Z-bar lifters and Trend pushrods that glide in Kaase Boss Nine alloy heads.

Modelled off Ford’s famous Boss 429 ‘semi-Hemi’ Shotgun heads (used to great effect in NASCAR) but improved with modern technology, the Boss Nine heads feature deep-breathing 2.30in inlet valves and 1.90in exhaust valves, with WW Engineering 1.75:1-ratio shaft-mount rockers.

On top of the Kaase EFI intake manifold is a Wilson throttlebody wired for Holley EFI, with the whole package polished to a fine shine, including the front drive accessories and cast rocker covers. A Kaase aluminium oil pump and custom oil pan handle the black gold and ensure the big-inch Boss will fit in the XB’s engine bay – a task made easier thanks to Ryan Carter and the United Speed Shop boys fitting one of their trick Magnum IFS front ends. Behind the big-block is a triple-plate carbon Tilton race clutch in a Quick Time bellhousing, and it will have a heck of a job holding the Kaase Boss Nine’s monstrous output.

All up, the big six-hunge made 1000hp on the engine dyno at just 6800rpm, twisting out 860lb-ft. “It has heaps down low,” Chris enthuses. “I really cannot wait to get in and drive it, and that is what the whole car has been built for: to drive.”


THE Kaase Boss Nine is based on Ford’s classic Boss 429 ‘Shotgun’ motor of 1969-70. While Ford had previously offered 427, 428 and 429ci big-block V8s, the Shotgun was a wildly different beast. Designed as Ford’s version of the Chrysler Hemi, it was sold only in limited-edition Mustangs to homologate the engine for use in the Ford Torinos being run in NASCAR.