Hi everyone, I’ve been working on this for a little while now and a few people have asked me to do a proper build thread on it, so I thought I’d better do it!
It’s divided up into separate blogs over on our website at http://www.mx5usedparts.co.uk/blog/, so I’ve posted it under separate headings etc for now.
Just so no one thinks we’re stealth advertising or anything - we run an MX5 service/repair and parts workshop which has basically evolved out of our love of fast road/track driving, and means that we (myself and bus. partner Adam) can spend more time doing what we love. For me, that means messing around with engines, modifying and playing with cars and making them quicker! I’ve buggered about with vehicles since I first owned them. I have total respect for people who want to keep their cars OEM and love to see a perfect restoration, but that’s not for me.
Anyway, here’s the first few installations:
Prologue
After messing around with my Legacy and pushing it as far as my insurance company would let me, I decided I needed a new project.
During my days a Car Hack (aka an ‘Automotive Journalist’), one particular project stuck in my mind. A garage who were successful enough to have their own rally team had purchased a MkII Escort. Full Mexico rally spec, panhard rod and Gaz shocks - nothing out of the ordinary. What was different, however, was the powerplant. Rather than the usual Pinto spec boat anchor of an engine, in the sizeable engine bay sat a 13b rotary from an RX7 FC.
ABOVE: I think this was the car I did a feature piece on…I mean I partied a lot during those years but you’d think I’d remember.
I remember being quite surprised by the fact there was next to nothing else in there alongside the tiny lump. Sitting low down in the bay, there were a handful of wires connected up to an Omex or a Megasquirt setup (I can’t remember). The stock manifold and intake ports had been discarded, and instead two fat steel pipes connected two massive throttle bodies to a peripheral port setup – ports directly through the wall of the engine housing rather than the smaller regular side entry ports.
See the vehicle running here
The car idled like shit. At low revs it was borderline undriveable, but once it hit 4000rpm it took off like a missile. It dyno’d at around 270-280 bhp, completely naturally aspirated and running stock 99 RON pump fuel. I was hooked.
The team (whose name still eludes me) were astounded at the advantages it gave them in rallying. Having that smaller displacement allowed them to compete with other 1300 rally cars – only with about 100bhp more. Similarly the lighter front end and lower centre of gravity significantly reduced understeer, allowing the driver to keep the front end on point whilst sliding round tighter corners.
Since then, I’ve always wanted something rotary powered. I know they’re a technological dead end until a suitable indestructible material has been invented to make those devil apex tips and housing coatings out of, but I don’t care. I never wanted this project to be about practicality. I wanted this project to be about making a balls-to-the-wall B-road missile, something which would embarrass a Scooby in a straight line and upset a Boxster on the country drive to the hairdressers we both worked at.
For years I’ve perused eBay looking at cripplingly expensive RX-7s, something I still hope to own before combustion engines are eventually outlawed or they’re all even bigger rustbuckets than they already are. But that’s a different story. As I’ve become more involved with the RX7’s shorter, scrappier younger brother (that’s the MX5 FYI), it makes perfect sense, both in its sleeper potential (very few MX5s are particularly quick in a straight line), but more importantly the chassis and driveline make it a perfect match.
I know it’s been done, I know there are cheaper ways to make an MX5 go just as fast, but for now the plan is:
- 13b Naturally Aspirated
- Bridge ported + polished
- Independent Throttle Bodies
- MS2 or MS3, depending on the bank
- Probably a custom manifold setup
- Custom Exhaust (obvs)
Watch this space.
Chapter 1 - A Nice Fella From Kent
In May I got in touch with a guy on Electronic Bay who was selling an RX7 engine. It had some overheating problems and was being sold as spares but it didn’t carry the ridiculous price tag of nearly anything else with ‘13B’ written on it.
I met a nice fella from Kent who was putting a Toyota 2JZ engine into his RX7. One evening after work I took a trip down there in the Legacy to pick up the engine. I helped him shove the bare shell of the legendary road car out of the way before we manhandled the 13B into the back of my estate.
We agreed on £60 for the engine which came with everything except the coilpacks, engine loom and ECU. I couldn’t argue with this price as I’d blown more in petrol getting there.
On my fifth coffee and starting to flag, thinking about the potential nightmares in front of me, but knew it was all for the greater good.
Upon getting it into the workshop I embarked upon a full teardown of this ridiculous engine. Surrounding the intake manifold was a rat’s nest of fuel and vacuum pipework. Nearly everything was manually actuated with pressure valves opening vacuum airways that allowed other stuff to happen.
Fuel pressure regulators, PCV (Positive Crankcase Ventilation) and oil metering injectors all ran from vacuum solenoids and weren’t electronically actuated like most modern engines that have these features. But removing or dealing with these was a nightmare for the future.
Some of the old plastic connectors had seen better days and were brittle.
After the waterpump came off, the two injector rails came out along with the maze of fuel lines and vac lines. Eventually after some coaxing, the inlet manifold came off, showing the primary and secondary manifold inlets.
After a while I had a pretty big box of engine ancillaries going on.
ABOVE: That JDM filler cap has to be worth at least £75.
Then I came up against the first major hurdle so far. It’s well documented (I learned retrospectively) that the 54mm nut on the back of the crank/flywheel is an absolute bastard. Nothing prepared us for this though. The first warning sign came when it positively laughed at our Snap-On impact gun. That thing tears rusted up rear subframe bolts out with little drama and even with a fully charged battery there was no sign of it even entertaining the thought of coming off.
ABOVE: By this point I was too mad to take photos so I’ve nicked this one off another website for reference.
After that there was a series of long extension bars including our metre long breaker bar with a huge 6ft pipe preventing the flywheel from turning, but with bulging veins and red faces we had to admit defeat on this one for the time being.
It was back to the drawing board for now.
Chapter 2 - The 54mm Deathnut and a Mild Engine Teardown
We’d been floored by just how tight the flywheel nut was on this engine. We had to get pretty creative in order to remove the thing.
Literally nothing we’ve had to undo comes close to the amount of torque required to remove this thing. We had an 18stone man (me) jumping up and down on the end of a metre long breaker bar. In physics terms that’s over 1100 nM of torque. This nut wasn’t messing about. We had the thing sitting in an engine bay with a thick section of steel gas pipe jammed solidly between the inner wings and bolted into the flywheel (with fine gauge threads that were actually quite hard to find), with an extension on top of the breaker bar.
Eventually I had a Jack Bauer moment of grim choice and got out the oxyacetylene. and heating up something which I really didn’t want to warp anywhere if it could be helped. The crank shaft (eccentric shaft or ‘E’ shaft as it’s known) could take some heat but if you heat metal up enough then it will warp. That’s science. That just how it works.
There was also the issue of the nut itself. We’d had an issue or two before melting alloy stuff before realising the melting point is only 600°. The nut looked like brass and we estimated it’s melting point at around 1000°. Hopefully we wouldn’t find out.
All was well and we were back relatively plain sailing. Off came the flywheel and out came all 20 or so of the housing bolts which go right the way through the engine and screw into the front iron, followed by the first rotor and a handful of seals.
Immediately apparent was a possible reason for the overheating – the system was full of gravelly shiny granules reminiscent of Radweld. The water pump rotated freely and thermostat had been recently changed – for now this was the most likely cause.
As the for the rotors themselves, they didn’t look totally bollocks, which was a plus. The housings, however, had seen better days. The minimum allowable wear of 2mm from the edge had been exceeded and in places multiplied. Interestingly the wear wasn’t of the usual concentric style around the edges but a staccato chatter style mark which indicated that the seals had been bouncing across the surface.
After asking some adults on a rotary forum (RX7club.com – cheers guys!), the grim confirmation came home that the housings were indeed bollocks as previously assumed.
Curiously the apex seals and the side seals seemed to be in good condition. The rotors are sealed with metal seals – apex seals on each of the corners and side seals between the rotor and the irons. Behind these are springs which maintain a light pressure behind the seal to keep it sealing. These looked to be in okay nick although they’d need to be properly tested for clearance later.
Now all I needed was a car.
Chapter 3 - Overspray, Bonnet Pins and an Actual Car
I had been cruising eBay for a decent looking shell for some months. Despite a few gems, they were nearly always accompanied by ‘needs welding for MOT’ or ‘sills need welding – have been quoted £7.50 for this by a man I met in the pub.’
Bollocks to that, if you’ve had the car long enough for the sills to start rusting then fair play to you. Buying into something I was going to have chuck a few hundred at before I even started was already pricing myself out of the game. I had way more time than money.
Until one popped up on eBay with a list of tasteful mods and an undisclosed mileage, but the magic words ‘no rust’. ‘No rust’ is a strong statement for anyone to make, and put me in a good position to haggle.
Not being too bothered about the condition of the engine was a luxury I’d never experienced before. Nevertheless, a sizeable oil leak also worked in my favour when it came to negotiating. From experience, this was more than likely caused by removing the air con pump without replacing the waterpump seal, which can easily result in a steady but manageable oil leak. We’d see for sure when the engine came out.
The main attraction was the fact it already had a TR Lane rollbar, V-Maxx shocks (cheap but very cheerful), and crucially – a hardtop. I had no intention of leaving without the vehicle but managed to agree on £650.
The paintjob was a point of entertainment alone. Evidently the 3L silver had proven too pedestrian for one previous owner and they’d snapped – making the trip to Halfords to blow £50 on satin white rattle cans. On closer inspection there was overspray on nearly everything that wasn’t glass. Even the exhaust and rear number plate lights had fallen victim to the snowstorm.
Once back in the workshop it was time, naturally, to take it to bits.
One mod I wasn’t too keen on was the racing style bonnet pins mounted on the bootlid. I planned on making the car at least a little bit streetable, and I live in Sheffield so I decided to return to the regular boot release mechanism.
One of the most exciting reasons for the vehicle being the workshop, however, was to test out something new we’d been working on - a set of reconditioned, blasted, prepped, etch primed and painted wishbones fitted with beefed up aftermarket balljoints. I figured this was as good a time as any to put them to the test. Although installing the balljoints was suitably onerous (as well as the massive circlip holding the thing in place), I just wanted to give them a few thousand miles of fast road/drift hammer purely for our peace of mind before they go on sale.
Plus it was an excuse to spend a day at Blyton on the company.
