TURBO GREY MOTOR
SWINGING FOR THE FENCES WITH HOLDEN’S HUMBLE AND BELOVED GREY MOTOR
Swinging for the fences with the turbo grey motor that powers Mark Riek’s superb FX ute
FOR those who didn’t catch our feature on Mark Riek’s sensational FX Holden ute in the June 2015 issue of Street
Machine, we’ll run you through the highlights. She’s a superbly restored old girl, powered by what’s probably the most hightech Holden grey motor in existence – at least since the days of the Waggott twin cam and the like.
Built by Geoff Scott from Geoff’s Auto Studio, it displaces 2458cc (or a whisker under 150ci), with the bottom end consisting of a lightened and modified crankshaft, a set of conrods pinched from a Mitsubishi 4G64 fourcylinder, and 81mm ACL pistons that would otherwise have ended up in a Mazda.
The camshaft is from Waggott, with .500in of lift and 232@50 duration, and the head is the factory grey casting that’s been ported and fitted with oversized valves and performance springs.
The induction system is trick: a custom inlet manifold, an electronic fuel injection system powered by a MOTEC M84 ECU, a PWR water-to-air intercooler, and – when we featured the car – a Garrett T25 turbocharger.
It’s a magnificent concoction of parts that took plenty of R&D to perfect, and with a tune by Rod Salmon at The Speed Shop in Gympie, Mark saw several thousand trouble-free miles with the ol’ grey making 141rwhp and 471lbft. That’s pretty impressive considering a standard 132.5ci grey motor is rated at just 60hp at the flywheel.
Back then, Mark told us he had aspirations of fetching 200rwhp out of the engine with further development, and when he snapped one of the dump pipe studs during a routine spannercheck, he got the excuse he’d been looking for.
“I was going to have to replace the exhaust housing, and I’d been toying with the idea of a bigger turbo anyway,” Mark says. “It all kind of snowballed from there.”
With the engine pulled from the car for some further development, we thought it was a great opportunity to take a closer look at what is a truly unique powerplant, and find out just how much power could be squeezed from a fulleffort grey.
The spanner work and tuning were handled by The Speed Shop, and consisted of valvetrain, fuel, ignition and induction system upgrades; a switch to sequential fuel injection and E85; and a host of driveline changes in the hope of surpassing Mark’s 200rwhp target.
Due to the siamese intake port configuration, the fuel system initially had just three injectors and the ECU was under the impression that it was running a three-cylinder, two-cycle engine. The switch to sequential injection meant a lot of changes.
“Basically we were trying to get everything we could out of it,” Rod says. “We did some homework and made a new alloy intake manifold from scratch with a Plazmaman 60mm throttlebody, because to go to sequential injection we had to run six injectors, and with only three intake ports, that meant two injectors per port. We used 410cc injectors and we went to LS coils and an EFI Hardware billet distributor to burn through that E85.”
Making the most of the switch to the higheroctane fuel, the turbo was upgraded to a Garrett GTX2863R with a dual ball-bearing billet turbine and a Turbosmart actuator and boost controller regulating boost to 17psi.
To withstand the extra punishment, the valvetrain was beefed up with Yella Terra rockers and Jet Engineering pushrods.
Having had vacuum issues with the Trimatic transmission due to the turbo, Mark swapped it out for a manualised Powerglide with a custom adapter plate and a 3800rpm TCE converter.
Once the car was back on the dyno, Mark and Rod were both stoked with the outcome. At 204rwhp and 17psi the injectors were maxed, meaning that there’s still more to be had from the old girl with upgraded squirters and more boost.
“In theory, the 410cc injectors we used should have been good enough to make 280rwhp, but they’re well and truly maxed at 204rwhp, so it’s drinking some fuel,” Rod says. “With that in mind, and the massive amount of torque it makes, it’s probably capable of more power than it’s showing on the dyno. Torque is up from 470lb-ft to 1100lb-ft, and while there’s been some gearing changes that would affect that, I’m comfortable saying that we’ve doubled the torque with the changes we’ve made, and it’s a completely different car to drive.”
Mark’s rapt, but he’s not all about dyno figures; he’s got some ET expectations tied to this latest round of mods. “The goal is to beat Bob Hamilton's Captain Nitrous FJ, which ran a 12.98; that’s been the grey motor record for ages.”
The car has only had two passes since the upgrades; a 13.247@99.52mph on 15psi, and a 13.201@99.88mph on 17psi, with the car running out of revs in the big end and finding the 6000rpm limiter on both occasions. Mark plans to bump the limiter up to 7000rpm, switch from 24-inch street tyres to a set of taller 26-inch ET Street radials, and is quietly confident of a result.