A few weeks ago, after making progress behind a rather quick Audi TT, I found the MX5 suddenly starting to lose power at the top end, which rapidly descended into a misfire and culminated with the engine dying just as I pulled onto the drive.
An unexpectedly full oil catch-tank and a refusal to start suggested something was amiss and an inspection with the borescope showed that pistons 1 and 3 had damage to the crowns. After a post-mortem, I suspect that when I refitted the trigger wheel to the crank pulley in a more robust manner (I was concerned that it may come off) it must have been a degree or so off, resulting in the ignition running slightly advanced. The car had been running like that for almost a year without any noticeable pinking nor change in power, so it must have been borderline. Either way, the damage was done!
The MX5 was dead.
After much wailing and gnashing of teeth, I stopped and considered my options. The supercharger project was pretty much complete, and there wasn’t much else I could do with the engine as it was without building it with up-rated rods and whatnot. A process that rapidly descends into the law of diminishing returns both in terms of time and money.
So, in lieu of just replacing the engine with the same again, and bolting on the same supercharger kit, what could I do?
I’ve long had a V8 shaped itch, and there are plenty of relatively inexpensive, second-hand V8 ‘Grand Tourers’ about like the Jag XK, but I’ve also spent a lot of time on my little MX5, not just under the bonnet but with the interior and custom audio/dashboard. It seemed the only real option was to kill two birds with one stone. Get the MX5 back on the road, but fit it with a V8.