Mx5 Rocketeer V6 Conversion Project

[Lewis's Friend]

daveinhampshire said:

Was having a browse through to see if anyone else was shoving big engines in MX-5's while mines tucked away for the winter and this one popped up! I love the work you've done, essentially a new car, really great job.

On the engine conversion I looked into the V6 before I did mine but went with a Rover V8, mainly because my first car had one and there are so many upgrade choices from superchargers to 5.4 litres etc. I got a 4.6 from a running P38 Range Rover with all the ancillaries for £550 delivered. Spent around 1k on megasquirt with a custom loom and another £1,500 on bits like stainless steel headers and so on. There was some welding but nothing that would scare most competent mechanics. I put a diff from a 323i E36 and used the lt77 gearbox, they cost less than £200.

Once I was done I had it tested and it puts out 240bhp and 250 lb/ft. The nonsense about the V8 being to heavy is just that, it may be slightly heavier but it's not noticeable and the engine sits slightly further back. It sounds great and goes like stink. The part which pushed me to the Rover engine are the upgrades. I bought another set of heads for £90, I'll be doing the heads and cam next winter and and winter after that the pistons and supercharging it. I always have something to look forward too. The only negative seems to be the sniping when you go to meets "so much work for so little power", never sure why people feel the need to put down other people's work. Anyway best of luck!

Thanks for the kind words. I wasn't initially planning so much work, but one thing has lead to another...!

I ended up chosing the V6 option, basically as that what what the kit was for. I'm not sure I'd back myself to fab stuff up to get another engine to fit. Plus the original gearbox etc could be retained for ease of install. I do like the RV8 though - a friend has a TVR Chimaera with the 4.0 and had that up to a rolling road verified 240bhp with work on the exhaust, intake, carbon trumpets in the intake plenum etc. Though now it has a large turbo strapped to it!

Part of me would like a V8, just for the noise. That said, the V6 in the demo car does sound good too, and I have some experience with the Jag V6 from my XJ (though in a totally different setting). There are tuning options with them too, though I would imagine at greater cost that the RV8. Mountune can build an engine to about 330bhp I believe, though I would need to remortgage for that probably, and I'm not sure if the gearbox etc could take it either!

[Lewis's Friend]

daveinhampshire said:

It's a bit splitting hairs really, either engine is awesome and with such low curb weight I'd be more than happy in either! I was a bit surprised the original gearbox and diff stay in on the conversion, more so the diff as they range anything from 3.6 to over 4 on ratio. I've currently got mine on a 2.93 which is a little low(removes wheelspin though) but couldn't imagine using much above 3.2 especially as the mx5 box ratios are low. Be interesting to see the speed in each gear, really you should be able to get a much stronger top end on the V6 and a much more relaxed cruise at 100mph

Just another mod I made, I vented the front wheel arches as when you build up speed the air pressure seems to build up. That seemed to solve it.

I understand the gearbox and diff are good for the power. Quite how much more they could take over the approx 260bhp that the demo car runs I couldn’t say though.

In terms of cruising revs, I calculated that with the 3.6:1 diff and wheel/tyre combo I’m after it should sit at a hair over 3000rpm at 70mph. Which is not super relaxing, but should be fine. In fact it’ll be almost exactly the same as my daily driver, a 52 plate Seat Leon Cupra R.

Also, do you have any pics of your arch vents st all?

[Lewis's Friend]

Again, thanks for all the positive comments - always appreciated.

Some more progress as I bolt more bits on. It feels like a lot of headway all of a sudden as the pile of bits diminishes, but still a ways to go...!

Front suspension started to be built up here:
1 by Jon Fellows, on Flickr

And at the back, droplinks attached to the ARB, and the reinforcers bolted onto the rear subframe:
3 by Jon Fellows, on Flickr

And lastly, a thrilling picture of a fuel filter! Just to show that I was sad enough to get even the little brackets coated...
2 by Jon Fellows, on Flickr

So next step is to lower the car to ride height and torque up the suspension bolts. Then it should be brakes on and bled, oil in the gearbox (diff already filled with Fuchs Syn 5), exhaust on and then trying to get it started and fault finding. There will be faults...!

[Lewis's Friend]

Paddy_N_Murphy said:

Re-iterating - the "Lovely Thing" I am loving what a brand new fresh look the MX5 is having / will be - never mind the V6 up front.
I'd love to have a project / place to potter like that.......

Thanks. I do like to have a project to play with, as it keeps me out of trouble.

I think I’ll have to be careful not to assume it’ll drive like a new car when I’m done, and then be disappointed that it doesn’t straight away. In the flurry of getting the underside sorted, there’s still the window that doesn’t really work, wing mirrors that don’t adjust, awful sound system, suspect immobiliser and other things that I relegated to the back of my mind as being ‘minor’...!

I’ll get there with it, but it won’t be perfect for a while yet!

[Lewis's Friend]

Paddy_N_Murphy said:

Not a bad thing

Just given mine a run out - there is a charm that a new car can't get near...

To be fair, I’ve never owned a new car, or even close to it so I don’t have much to compare it with...! I tend to only start being interested in a car after it gets to about 10+.

[Lewis's Friend]

anonymous said:

[redacted]

I had one of these in my XJ. It would cruise at 70 at about 2000rpm, but would go if required. It was amusing to try and hustle it, but not really it’s forte...!

[Lewis's Friend]

Paddy_N_Murphy said:

Lewis's Friend said:

Paddy_N_Murphy said:

Not a bad thing

Just given mine a run out - there is a charm that a new car can't get near...

To be fair, I’ve never owned a new car, or even close to it so I don’t have much to compare it with...! I tend to only start being interested in a car after it gets to about 10+.

Tempt you in a 911 that I need to move on ??

Sadly not after what I’ve just spent on a Mazda...!

[Lewis's Friend]

HustleRussell said:

My earlier comment about the money side of this was taken as a negative remark, for that I apologise, we’ve all spent more on cars than the cold hard sums could justify (myself very much included). Some cars are greater than the sum of their parts because they are unique or represent a ‘journey’ in themselves or are the culmination of our hobby.

Looks like you’re doing a great job of it

No worries.

I have to say I used to wonder why people spent such sums on personalising cars etc, when you could just save up and buy a more expensive, ‘better’, car.

Obviously nothing wrong with that, but I find now I enjoy doing projects on the cars as much as driving them afterwards. Hence all this now!

[Lewis's Friend]

I managed to get a bit more work in the last couple of days, so another post for all those who came here to see an engine swap and have in fact just seen a suspension rebuild!

First, I torqued up the suspension bolts. To do this, I needed to drop the car to ride height, which I did with even more axle stands. Luckily I have a stupid amount of them collected of the years!

Rear suspension compressed for torquing up:

IMG_2786 by Jon Fellows, on Flickr

IMG_2785 by Jon Fellows, on Flickr

With this done, it was the same story at the front, after fitting the brake gaurds and front hubs. This is after the torquing:

IMG_2787 by Jon Fellows, on Flickr

I then needed to fill the gearbox with oil, having done the rear diff previously. This requires a bit of bodging to get oil into the filler hole, but a bit of hose and the bodger's friend (tape) got me through! So some Fuchs Gear Syn in the gearbox.

IMG_2788 by Jon Fellows, on Flickr

This brings me onto todays work - brakes.

This was quite nice, and is also one of the last pieces to be bolted to the car from the pile of refurbished parts in the living room. Naturally its never quite as easy as you think it will be, but it wasn't too arduous, and now I have brakes! No fluid in them yet, but little steps...

IMG_2790 by Jon Fellows, on Flickr

IMG_2791 by Jon Fellows, on Flickr

IMG_2792 by Jon Fellows, on Flickr

IMG_2793 by Jon Fellows, on Flickr

IMG_2795 by Jon Fellows, on Flickr

So thats it for this update. Finally getting there I feel, though lots of little bits to go still to tie it all together.

[Lewis's Friend]

threespires said:

Congrats on such high quality work and thanks for updates..........

Thanks, that's kind - and nice to know people are interested!

[Lewis's Friend]

I will admit the calipers and pads lend a slightly funky aspect to the look, but I hope it'll all work out when my new wheels are on and the gold stickers removed.

Time will tell!

[Lewis's Friend]

MX6 said:

This is looking great, the standard of the build looks really good, keep it up! I really like the bright orange caliper paint, I'm thinking of going with that for my MX6. I'm not completely sold on the two-tone look though with the green carriers, but it will look good regardless.

Thanks - the green is actually just an unfortunate by-product of using EBC Greenstuff pads. The carriers are orange too. Still, I guess it wont take long for the pads to turn black with filth anyway, so then the two-toneness will be incidental!

[Lewis's Friend]

Work has slowed a little of late, for a few reasons. Being snowed on cooled my enthusiasm a little, plus I may have purchased another run-around which needed a little work. I think of it as a cousin to the finished MXV6....!

IMG_2797 by Jon Fellows, on Flickr

Its got the same 3.0 V6 as I have sat on a pallet in the garage for the Mazda, so come service time, I'll just buy two of everything.

I have managed a little more progress on the MX5 too though, but no major leaps forward. One thing I needed was a rear exhaust heat shield. They are about £35, and would just eventually rot out again. You can buy aluminium units from Jass Performance for example, but the basic shape was very simple so I thought I'd have a go at making my own.

This was my effort:
IMG_2800 by Jon Fellows, on Flickr

It fits OK, after a little trimming, so will hopefully be up to the job. Here it is in situ:
IMG_2804 by Jon Fellows, on Flickr

IMG_2805 by Jon Fellows, on Flickr

The other work I have started is regarding the front bumper. I wanted to relocated the numberplate to a side mount, as I think it cleans up the whole front of the car. Plus the numberplate was badly attached with self tappers. However, on removing the numberplate, I found a rather excessive nine holes drilled through from previous plates...! Some large from the factory plate carrier, and some small from random bodging in its past...

So I set about filling the holes - notice the commitment. Not even fully thawed out!
IMG_2803 by Jon Fellows, on Flickr

Many holes....
IMG_2802 by Jon Fellows, on Flickr

Filled and rough sanded
IMG_2806 by Jon Fellows, on Flickr

And wet sanded ready to be shipped to a buddy who will 2K prime it and send it back for me to flat.
IMG_2811 by Jon Fellows, on Flickr

And that pretty much brings me up to date. Steady, if not rapid progress is being made!

[Lewis's Friend]

C70R said:

573 said:

Lewis's Friend said:

Thanks - the green is actually just an unfortunate by-product of using EBC Greenstuff pads. The carriers are orange too. Still, I guess it wont take long for the pads to turn black with filth anyway, so then the two-toneness will be incidental!

The more unfortunate by-product of using those pads is that they are utterly pants. They bite worse than cheap motorfactor pads yet if you take the thing anywhere near a track they'll overheat and crumble to dust in minutes.

Agreed wholeheartedly. I've had better heat-resistance and stopping power out of OEM spec pattern pads.

I have heard that unfortunately. I had Yellowstuff pads on my TVR, and they were OK, but time will tell I guess.

I'm not intending on doing any crazy driving on track etc in the next year or so, so if they are OK for a while and I then change them for something more performance orientated in the future then I'll be happy enough (though prefer them to be good out of the box of course)...

[Lewis's Friend]

MX6 said:

Oh I see now, my mistake! In my defense I was viewing on the small phone screen previously... Yes the pads will look better when the green isn't standing out quite so much, but function is more important and I'm sure the Greenstuff pads will be a nice upgrade for the anchors.

Anyhow good to see some progress, at least the cold weather has backed off. I really like the S Type, like all Jag's when they get older, they are a real bargain.

Cheers - its definitely more pleasant working in temperatures above freezing!

And Jag S-types are very cheap. Possibly with good reason... The looks, how can I say, divide opinion, they have a rather dubious build quality rep (at least the early ones) and can be pretty juicy to run. That said, this one looked a bargain. I guess time will tell whether it is or not!

[Lewis's Friend]

Greg_D said:

looking at how much effort you have put into the undercarriage, have you heard of cryo blasting?

i don't know much about it, but rumour has it one can blast all sorts of crud off things like the diff housing/bushings/wiring without taking everything apart and it end up all spangly looking with minimal time/outlay. apparently it's golden for things like wheel wells/gearboxes/diffs etc.

i'm no expert in it, but it's got to be worth a google...

I haven’t heard of it I confess, I’ll have to check it out.

I did originally plan to clean up and polish the diff, but when it came to it I didn’t want to slow the build by that much (plus it’s a horrible job!).

[Lewis's Friend]

Re. the EBC bits and bobs, I’ll report back when it’s on the road. Hopefully they’ll be a performance revelation and I’ll never have to change them!

[Lewis's Friend]

Right, time for another update.

Work has been progressing, but not as fast as I would like. I think that's partly because it feels like I'm almost there in terms of having her back on the road, and then every setback seems even more frustrating than usual.

Sadly for me, I recently bled the brakes with the help of Beloved. This ended with me snapping a bleed nipple off in the nearside rear brake caliper. Extremely vexing...! Particularly as I have no one else to blame but myself. I was just a total klutz. I can't get the stub out either, so have chosen to buy a breakers caliper and have it refurbished (again). Of course that takes time, so I must possess my soul in patience until it returns. Ah well...

In better news, my front bumper has moved on, as can be seen here mid-way through flatting.

IMG_2825 by Jon Fellows, on Flickr

And here it is back from my buddy, and fitted to the car.

IMG_2844 by Jon Fellows, on Flickr

This is totally as it was when I picked it up, so has not been flatted or polished in any way. The clear sits just as it left the gun! I'll flat and polish it up when I do the rest of the car (which is filthy now), but fitting the bumper a) made me feel like some progress had been made and b) keeps it rigid and easier to rub down.

And another picture, just for good measure..

IMG_2845 by Jon Fellows, on Flickr

I've also sorted out my new wheels. I thought I might keep the original set on for a while, but on closer inspection the tyres where cracked and rubbish, so new wheels and tyres it was! I originally wanted Enkei Apache II wheels, but when I ordered them, I discovered that they've stopped making them in Mazda PCD (4x100), so had to change my plan.

I've gone for Japan Racing JR6's. Not my first choice, but they're growing on me.

IMG_2838 by Jon Fellows, on Flickr

And I ended up getting Yokohama AD08R's fitted to the wheels. Now I just need to finish the brakes, so I can fit the wheels and get driving!

IMG_2840 by Jon Fellows, on Flickr

And that's the end of this minor update. Mainly about how not to bleed brakes!

[Lewis's Friend]

Super Slo Mo said:

Cracking project, I’ve been following this one for some time, I love things like this.

I’m really sorry to be pedantic though but you have your gear ratio terminology inverted: a 2.93:1 ratio diff is a higher ratio than a 4:1.
It gives a higher output speed for a given input speed, that’s how we refer to a gear ratio in terms of ‘high’ or ‘low’.

It’s not based on input speeds because your input speeds (or range of input speeds) are fixed.

Your output speeds are entirely dependent on the gear ratio (and of course the ability of the engine/power unit to drive it).

Thanks for the kind words.

And don’t feel the need to apologise for correcting errors. I’m always ready to be told I’m wrong!

[Lewis's Friend]

MX6 said:

Good to see the progress. I really like those new wheels, they look period correct on the MX5 and a lot more muscular with that dish to them compared to the original rims...

Thanks. I think Mx5’s can pull of a number of different styles of wheel to be fair. But I wanted to go down the more retro kind of route.