PLENTY OF US have good – or maybe not so good! – little-kid memories of the back seat of a Chrysler Sigma, one of Australia’s most popular family cars of the 1980s. But even with the ground-breaking Sigma Turbo in the model range, it’s not often you read ‘Sigma’ and ‘performance’ in the one sentence.
Jason’s is not the first Sigma to front up at Drag Challenge – Sydney’s Domenic Pelle brought an turbo LS-powered Sigma to DC last year and is bringing it back this year – but with the build of Jason’s Sigma being a development program for his Muscle Garage/Tuff Mounts bolt-in engine swap kit, it’s certainly not going to be the last V8 one we see, either!
But that’s not to say you can’t bulk-up a Sigma… as Radelaidian Jason Waye hopes to prove at this year’s Street Machine Drag Challenge. He’s shoved one of GM/Holdens formidable all-alloy LS1 V8s into one!
“It was dying to be done!” chuckles Jason, the boss at Muscle Garage and Tuff Mounts.
Why a Sigma? “I saw a Sigma when I attended Drag Challenge Weekend in Queensland and I thought – what a great idea! They have a big engine bay!” There was another reason, too – Jason wasn’t confident he’d get his Barra-powered 1980s Ford Mustang completed in time.
The due-by-DC build began in late June. A few mates around the country kept their eyes open for a suitable project car but Jason found his Sigma – already swapped with a carby Holden V8 and Trimatic – in Victoria.
This Sigma was re-painted when the carby Holden V8 was dropped in. That was around 20 years ago so it’s not perfect – but it’s certainly nothing to be ashamed of. For DC, Jason has fitted a reverse cowl bonnet. Inside it has its grandma-comfy quilted-and-buttoned top-line trim but Jason will be driving DC with a Kirkey drag-spec alloy seat in the car so he can fit the cabin with a helmet on!
To repower it, Jason bought an ex-WK (VY) Statesman engine, trans and ECU/loom. Showing 140-ish thousand kilometres, it was disassembled for a look inside. The heads were sludged with carbon so were cleaned and serviced with new springs and stem seals. The piston/rotating assembly – and compression – wasn’t touched, but a VCM 710 cam and oil pump kit was installed before Jason made it all fit the Sigma engine bay. With the modest mods it makes 260kW at the wheels.
Big-engine, smaller-body sleepers have been a part of street machine society for decades. But not all sleepers make sense. Just because you can, doesn’t mean you should! The Sigma makes sense: the engine bay has plenty of clearance and the stout body can be torqued up with big power without popping the door latches. The beefy body – and its weight – plus parts interchangeability with other Aussie cars (such as brakes) make it a relatively simple engineering exercise and a great home for a V8.
The 4L60E four-speed overdrive autos aren’t known for strength under pressure, so it was rebuilt with upgraded clutches, bearings and valve body.
“Done properly, these are a reasonable trans,” Jason reckons. “I wanted one because it needs to be a road car for Drag Challenge – not just for down the strip. If you pump up the pressures and change the shift points in the tune, it doesn’t work for long; you need to do it properly internally.” The JRM Transmissions-built ’box runs an AK 3600rpm convertor and fits the Sigma trans tunnel with little more than a few hammer hits for clearance. The rear axle is a narrowed ex-Commodore BorgWarner that was already there.
“It already had a lot of the stuff we needed,” says Jason of his bargain buy. “Buying it like that [with a V8 swap] didn’t make the engine transplant any easier but it saved us time and some money as it already had a [tougher transplanted] diff in it and it had bigger V8-spec VR Commodore brakes all around.”
Now the car is completed and registered, Jason knows from test launches that it has a tricky torque-bias type centre in it, too – but he’s not sure what brand!
“It was a pretty quick build, really, and I can’t wait to hit the road in it!”
Jason will be contesting the Tuff Mounts 235 Aspirated class at Drag Challenge.
1981 MITSUBISHI GH SIGMA
Engine: GM/Holden LS1 5.7-litre alloy V8
ECU: Holden LSI with modified loom
Trans: GM/Holden 4L60E four-speed auto
Convertor: AK 3600rpm
Diff: Holden/BTR with 4.1 cogs and torque-sensing diff