The original plan was to build a replacement for my old MK Indy 7 clone kit car. I owned this when I was married and I loved it! 500kgs, 160 BHP and an 11,000 RPM rev limit due to having a Honda Blackbird engine makes for quite an intoxicating drive.
However, with a divorce to pay for and some outstanding debts to clear, I had to sell it. Which was a real shame as I loved having my little toy car. But now she's off in the Alps hopefully having a lot of fun. So the aim of making something at least as quick but more practical came about. More practical because owning a 7 is fun, and I've done a full weekly shop and even fetched 7' tree stakes in it but having a heater and a boot would be nice so I can go touring in it and maybe even persuade my partner to come along occasionally. But not often though. She tells me off too much for that......
So the search started for ideas. I didn't have any one thing in mind as I was open to just about any sort of project, but I was leaning very quickly towards something small and light as that's how I like my toy cars. It makes them cheaper to run and look after and parts tend to last longer. They're also a more engaging drive. And they fit in garages with space to work on them too!
One day I got a call from my partner saying a bloke at work had been told my his Mrs to get rid of the car he'd not really been working on for the past 4 years. Following a few questions, he didn't really know much about what the car was and he thought it might be an MG Midget. Since he only wanted £100 for the car and the boxes of bits, I figured it was worth a look. Upon closer inspection, it turned out the car was an 1969 Austin Healey Sprite, not a Midget, and it was complete but had seen better days. It also isn't registered in the UK as it's a left hand drive US market car. This also means it had spent most of it's life either in garages in the UK or in Florida where it's nice and dry. Whilst I hadn't planned on a full re-build, it seemed like a good challenge so £100 soon changed hands and the car was trailered home.
Upon closer inspection, and initial strip down, there was a bit more rust than I had hoped but less than I feared. Some fool had also tried to fit some form of arch extensions to the sills on both sides by brazing on steel plates and then covering them in 1/2" of filler! But overall the shell only needed what seemed easy work and a plan was hatched to change the engine and up the power.
From researching what can be done to these little cars, it soon became obvious that the engine of choice is Rover's K series engine. It's a lightweight, all alloy engine that is very light and comes in 1.4, 1.6, 1.8 and 1.8VVC versions ranging from 110 bhp up to 190 bhp for Lotus's VHPD version.
So off I went to Ebay, looking for a decent 1.8 VVC engine. I even bought one along with the better alloy inlet manifold and ECU. But then I had a thought. To beat the MK Indy, I wanted more than the 300 bhp/ton that it had. And in a 750 kgs car, that means having 225 bhp. Which as it turns out is quite a bit for a usable N/A K series. It's doable, but means spending quite a bit more money than I had in mind. So the K series got sold.
So a re-think was in order. I've always wanted, but never had a V engined car. So a bit more research dug up Mazda's KL 2.5L V6. It's tiny for a V6, all alloy and 160 bhp in stock form. But with the addition of individual throttle bodies, or ITBs, it'll make 205bhp, along with a good dollop of torque. It's also a nice revvy thing, with a factory limit of 7200 rpm which can be safely raised to 8,000 rpm. Now this was starting to look more like it. With a hike in compression, easily done with JDM spec pistons, and maybe some reground cams, a nice 225bhp should be achievable. OK, it's a bit bigger than the K series, but given all the work I had planned, what was a little bit more?!
Now, when taking a 40 year old car and quadrupling the power it has, there are a few other things you need to consider. Can the shell handle it? Will the brakes stand even a bit of a chance of stopping it? Will the tiny little back axle last for more than 30 secs? Is the front suspension any good? Is this a good idea, and has anyone else done it for hints and tips?
And for the Sprite, the answer is mostly no to those questions! The shell could cope, but I decided to reinforce it anyway in several places. The brakes? Not even worth considering. So it's MGB 10.75" discs with 4 pot Wilwood callipers at the front and 9" discs at the rear. The back axle? A standard A series can snap one, so the V6 would mash it in moments. A full De-Dion set up from the back of a Caterham Superlight should do the trick though. The front suspension? Dubious at best and needs greasing more than I want so it's going to be replaced with a double A arm coil over set up. It might have inboard coil overs to aid with packaging and ride height adjustments, but that's not for definite yet. As for it being a good idea, yes it is. No-one else I know of has done this to a Sprite before but I do know of one other chap fitting the same V6 as he's been asking me for advice. So at least one person thinks I know what I'm doing!!
So that's the plan, but where am I now? Well the shell's pretty much done. There's some minor work to do on the front suspension mountings and I have to re-build the transmission tunnel to fit the MX-5 gearbox I'm using but that's all done. The rear brakes are sorted as Caterham have done all that work for me as part of the De-Dion set up which is now complete. The front end will be built as a whole, so that's still to do. I've got a vague plan in my head for that, but that's all at this point. The shell's currently sat in the garage awaiting the completed workshop so I can set to again with making the engine and gearbox mounts.
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