Some people take up crosswords. Others tinker with model railways. Me? I play the increasingly Kafkaesque game of “Guess That Bracket” on a Mazda BP4W engine – a game involving rust, swearing, and multiple false leads courtesy of the internet’s collective misidentification skills.
Let’s start with the bracket bolted to the block – the silver painted thing to the right of centre - a hulking steel lump that looked as though it had wandered in from a bridge-building project. I knew it wasn’t the alloy PAS/A/C support bracket listed under every part number from here to Hiroshima. No, this one was forged by the gods of power steering and air con, back when belts were serious business. Only thing is, I’m not using PAS (at 800-900 kg the GT6 doesn't need PAS), and any air con in my build will be electric – not bolted to the side like a Victorian pump house. So out it came.
But not without a fight.
Of course, the final bolt was buried behind a sleeve, because Mazda are masters of putting fixings in places only accessible to dislocated wrists or divine intervention. I eventually had to mutilate a 14mm ring spanner and prevailed, probably aided by some obscure Norse deity of rusted Japanese hardware.
As it transpired, the sleeve must have been pressed in after the bracket had been bolted to the block, but I didn't know that, not that I could have pressed it out anyway, as I don't have the necessary tool (note to self - get another tool).
That left the EGR system (Exhaust Gas Return) – a wheezy, sooty spaghetti of pipework designed to please late-'90s emissions legislation. Not needed here. I’ve no plans to submit this engine to the DVLA as a BP4W, nor is the EGR relevant if it’s going into a vehicle of a certain age. The MOT doesn’t care, provided there’s no smoke and no lights on the dash. So into the scrap box it went to join the bracket, possibly to be reborn as a supermarket trolley in Swindon.
With the PAS and A/C gone, I’m left with a crank pulley that looks like it’s moonlighting as a ship’s capstan. Half of it serves no purpose now, so I’m getting a custom aluminium one machined – lighter, better balanced, and not designed to haul unnecessary belts. If the price is right, I might even have a couple of hundred knocked up and flog them on eBay. Enthusiasts of a similar persuasion could use them to rid their engines of that surplus ironmongery that Mazda thought essential in 1999, but are surplus to requirements on a restomod.
Lightening your crank pulley doesn’t change measured BHP or torque, as the standard equation reflects steady-state output only. But according to Newton’s second law of rotation, reducing the pulley’s moment of inertia means the same torque produces faster angular acceleration. So while peak power stays the same, the engine revs more eagerly and feels more responsive.
Some people do yoga. I delete emissions systems and fabricate new pulleys. We all have our coping mechanisms. But you're never too old to learn.
Now, I’ve rebuilt several MGB engines before – a simple, agricultural lump that practically strips itself out of sympathy. This BP4W? Different beast entirely. Fuel injection. Cam sensors. The sort of thing Lucas would’ve described as witchcraft. But the payoff in performance will be worth it.
I decided to test-fit the engine to the old chassis – not the one I’ll use, it’s down the garden and I didn’t fancy lugging it to the house. With the front end chopped off the old chassis, dropping the engine in was surprisingly civilised. Having the tub still on it helped – gave me a good idea of how much reshaping the scuttle needs. Looks like I’ll need to get the grinder and welder out to create a 4–6 inch recess that will need strengthening around the edges..
One mistake – should’ve mounted the coil packs first. They’re more prominent than I thought, and it’s always the bit you leave till last that gets in the way of everything else.
Still, fitting a slimmed-down crank pulley will give me bags of clearance over the anti-roll bar. Only snag? I can’t run an automatic gearbox – no accessory pulley means nowhere to drive the pump. Not that it matters. The purists would say any British sportscar with an auto box is heresy. They’re probably right. Having the gearbox attached might have proved helpful in tilting the engine sufficiently to get it under the firewall scuttle, but it was only a first fitment.
The term firewall on a GT6 or Spitfire is misleading when the transmission tunnel covering the gearbox is made from cardboard. It's like calling a tea towel a blast shield. The term firewall conjures up images of aircraft-grade insulation and bulkheads capable of withstanding napalm – not something that will merrily combust the moment it sniffs hot oil. Realistically, it’s the difference between getting away singed and being flambéed in your footwell. I shall be making something out of carbon fibre, I think, as the aesthetics of the original design are somewhat Spartan, and I need accoutrements.
So the plan continues. The engine gets lighter. The bay gets simpler. And the brackets, slowly, one by one, get correctly identified. Eventually. And refurbished as necessary. It no longer looks, as a friend commented recently (yes you, Pete), like it was dredged from the bottom of a lake.
I also want to put a removable crossmember under the gearbox. The logic is that I can drop the box for a future clutch replacement without having to hoik the entire engine out. Given the need for torsional strengthening, it will require some careful thought as to how I accomplish it - high-tensile steel and bolts.






































