A Superformance in Australia

[Aussie Mike]

Bernie, I believe the Robnells were running the 429 motor which is a 385 series Big Block the same as the 460. The original Cobras ran the FE motor in 427 and 428 cube versions. It's a much older design than the 385 series.

Camerons Car is a beautifuly turned out machine. Its well built with all the creature comforts and still churns out amazing lap times on the track. he's running a Windsor based motor but I believe the Windsors days are done for new Cobra builds. Strict emissions laws will make getting a car registered with one of these motors very difficult.

If you are determined to run a Ford then you will probably be stuck with the 5.4 modular motor from the Falcon. This will give you some grief squeezing it into the engine bay as it's DOHC heads make it 900mm wide. It's not the lightest power plant either at 279KG. It runs an Iron block and the size of those heads even though they are aluminum adds a lot of weight. I believe the 4.6 mustang variant is a little narrower due to it's shorter deck height and a bit lighter with it's alloy block. Technically I'm not that impressed with this motor as due to the blocks tight bore spacings the only way to increase it's capacity is to increase the stroke. The 5.4 is actually under square with it's stroke longer than the diameter of it's bore. This is great for torque but not so great for revs which is dissapointing since the 4 valve heads have the potential to flow a lot. The only way I've seen these motors make serious power without breaking the bank is with forced induction.

That being said the stock 260 or 290 KW Boss motor will make your Cobra into a tyre frying road rocket. The cars light weight means a Cobra doesn't require a lot of power to give frightening performance.

If you can get past the badge I've got an internally stock LS1 that is probably making 300KW at the crank. It doesn't take much to make good power with a stock motor. A remapped ECU, cold air and a free flowing exhaust will wake it up. The cams in these motors are pretty lazy due to the emissions requirements. Adding a cam, springs, bigger injectors, after market manifold and more dyno time and that number will be pushing towards 400KW at the crank.

If you aren't satisfied with that then you can bore and stroke the LS1 using an LSX (Bowe Tie) block from GM and take it out to 7.6 litres. This block supports a 4.25" bore and adding a 4.1" stroke crank gives you 465 cubic inches. or if you just used a 4" stroke crank you would have 454 cubes. These are the same dimensions as the original Big Block Chev 454. The LS1 has almost the same length rod too at 6.125" versus the Big Blocks 6.135"

A 4.2" bore and a 4.1" crank will give the same number.

The magical 427 number can be had by using a 4" stroke crank and boring the block to 4.125". I like the idea of leaving a few over bores in the block so the slightly smaller bore appeals to me. These are the demensions of the new LS7 motor used in the 2006 Z06 Corvette.


To put this into perspective the later FE motors with aluminium intake manifolds like the 427 and 428 weighed around 280KG and made a factory rated 317KW.

The original Big Block Chev 427/454 weighed in at about 330KG and made similar power.

The new LS1 and LS7 motors weigh around 180KG.

There's an Aussie Superformance getting one of these shoe horned into it shortly.

Cheers