CHRIS Demetriou was tempted to stick a big-block Chev in his tough-as-nails Pontiac GTO, and Con Sagiaris from Pro Race Engines tried to talk him into one to save some dollars and make more power. But in the end he stuck to his guns and went with a traditional Pontiac motor, and after seeing the mill on the engine dyno, he’s absolutely rapt that he did.

Pontiac motors aren’t really the done thing; parts are expensive and hard to come by, and their design makes them a bit of a challenge to work on. And if you want to make any kind of decent horsepower, you need to go with an aftermarket block – about twice the price of a conventional Dart Big M Chev block. Ouch.

Anyway, Chris still really wanted to keep his Pontiac GTO powered by a Pontiac V8, so Con screwed one together with a Butler block, Edelbrock heads with Butler’s own CNC program through them, custom hydraulic-roller Crane Cams bumpstick, and a APD 950cfm carb.

Twin-turbo small-block Chev engine dyno – Video

It’s a mild 535ci big-block combo built to make loads of low-end torque on 98 pump fuel and be nice and streetable. Chris is going to drive this car around and isn’t too fussed about quarter-mile times; he just wanted to see close to 600hp from the thing.

As is often the case, Con gave him a bit more, and the motor saw 688hp and 677ft-lb on the dyno, which was a big surprise for Chris. The engine has a relatively small camshaft for its size, so it was never going to make crazy horsepower, but it reaches peak power before 6000rpm, and at 4700rpm it’s making 600hp on the dot.

Even Con and Danko from Adicted Performance – where the engine was tuned and dynoed – were surprised.

“I’m happy with how it came up,” Con says. “This one fought us most of the way just because you can’t go and buy parts off the shelf for it. Apart from the rods, which are big-block Chev items, everything came from America.”

“Then there’s weird things like the cylinder banks are opposite to other engines so it’s like swapping left and right, which also changes the way the distributor turns. Then it wouldn’t bolt up to the engine dyno!”

As for the car itself, it’s going to be one seriously cool bit of gear. The ’66 GTO has been at All Race Fabrications to be tubbed with a big 295 radial tyre and nine-inch diff, brand new suspension all ’round and Wilwood brakes.