MX520 2.O

[NC85ST]

Nice work! Can’t wait to see it finished.

[nevdrum]

Almost finished front suspension dry build. Will finalise this in next couple of days and then get cab back on to sort out engine and gearbox mounts

 

 

 

 

[nevdrum]

Back on four wheels. Bit of a milestone for me! Time to put cab back on and also give the garage a good tidy…

 

 

 

[projectrally]

Looking good!  What year is your donor Miata?  

[nevdrum]

Thanks. I’m buying parts as I go. MX5/Miatas rust like crazy in the UK, so mechanical parts are plentiful and cheap. All subframes and suspension are NB, I have a 40-50K 1.8VVT engine lined up with loom and ecu. Will use a NA 5 speed gearbox so I can shorten the selector linkage and stick position 4” further forward as I want to keep the bench seat if I can.

[projectrally]

Nice.  I’m watching with extreme interest.  I’ve been making one good a Mazdaspeed Miata (the limited-production NB model with the factory turbo) out of two lightly crashed ones.  I have a full set of mechanical components and wiring just sitting in my garage right now.  Subframes, suspension, brakes…all of it.  

 

I also have a 77 620 King Cab with an SR20DET swap, so I don’t much care about swapping the drivetrain, but I’d like to put the front and rear suspension in it.  I’d get a nice power rack and pinion setup with double wishbones at each corner, a limited slip rear, and disc brakes all the way around.  Then the truck would handle and stop on par with the way it goes…

[nevdrum]

Cab back on chassis today. Just sitting loosely with fenders and bonnet only resting to remind me what the truck looks like. I need to cut/massage inner arches to get the front to sit lower (they need to be redone anyway to connect to strut top mounts - silver bits in previous images). Rear and front suspension sitting too high but won’t adjust until diff/rear tray and engine/gearbox in. The good news is that it appears I will be able to use a NB gearbox as no need to move shifter forward and keep bench seat. Biggest issue may be handbrake. I will either move it forward from standard MX5 position, or use a handbrake between seat and drivers door. All up, nice to see it looking like a vehicle again! And garage gets a tidy now…

 

 

 

 

 

 

 

[nevdrum]

On 1/17/2025 at 4:12 AM, projectrally said:

Nice.  I’m watching with extreme interest.  I’ve been making one good a Mazdaspeed Miata (the limited-production NB model with the factory turbo) out of two lightly crashed ones.  I have a full set of mechanical components and wiring just sitting in my garage right now.  Subframes, suspension, brakes…all of it.  

 

I also have a 77 620 King Cab with an SR20DET swap, so I don’t much care about swapping the drivetrain, but I’d like to put the front and rear suspension in it.  I’d get a nice power rack and pinion setup with double wishbones at each corner, a limited slip rear, and disc brakes all the way around.  Then the truck would handle and stop on par with the way it goes…

Projectrally do a search here for ‘project mx520’. That is the original build like this done by Bob Boileau - I’m unashamedly copying most of his build. The thread is very thorough. Also YouTube ‘those racing guys’ who were doing the same sort of thing - shows a bit of the subframe notching etc. there is also a good YouTube series of 4 vids by ‘driftworks’ - search for ‘Hi5 mx5 hilux’. They have put a turbo mx5 with subframes into a RN10/RN13 series one hilux. Another good look at other ways to solve issues in an almost identical build. Bob also has a 620 project thread on this forum, but I haven’t looked at it yet - may be my homework for tonight.

[projectrally]

Oh, I've seen it.  I've read through it all at least twice, but the quality of phone photos has improved a lot since Bob's build.  And being here live affords me the opportunity to ask you questions as you go.  Also, just seeing someone else attempt it is encouraging, you know?

 

 

[nevdrum]

18 hours ago, projectrally said:

Oh, I've seen it.  I've read through it all at least twice, but the quality of phone photos has improved a lot since Bob's build.  And being here live affords me the opportunity to ask you questions as you go.  Also, just seeing someone else attempt it is encouraging, you know?

 

 

No probs. I don’t think I’m in Bob’s league, but happy to show what I’m doing and take requests for specific photos and details. I’m very surprised after the excellent results and detailed build thread that more people haven’t done this conversion. As well as making the Datto drive a lot more modern, it significantly ups the reliability and reduces maintenance hassles and parts availability. Mine will look totally stock except lower stance and chin spoiler- I’m after a bit of a sleeper. 

[nevdrum]

Not much progress in the last couple of weeks. I’ve tidied up the rear top shock mounts to give better access for tightening the mounting nuts, and lowered the Meister R Sportivo coilovers to the lowest possible setting. My rear mount points are lower than the standard MX5 height, so I may have to get custom coilovers made for the rear at a later date - I will wait until tray is back on the rear to see final stance in the current set up. This weekend I’m hoping to clean and refurbish the steering rack. I’m still waiting for an engine, but next major step is engine and gearbox mounts and installation. I’m off to NZ to visit family in a couple of weeks, and I’ve taken the chance to order some Datsun parts I can’t get economically in the UK - some body rubbers and Cab body mounts (Im hoping those off a 620 will work). Plenty of minor body fab and clean up to keep me busy. 

[nevdrum]

These are the slots in the rear strut top mounts to make tightening the mount bolts much easier

 

[nevdrum]

I’m still waiting on steering rack mounting bolts, so in the interim I’ve started a task I’ve been putting off. The PO+1 hacked up the front end panels in order to fit a Buick/Rover V8, for which he needed lots of room. He hacked out a lot of the radiator support structure, which I’m going to fabricate and weld back in. Of course, this is the reason I ultimately got this vehicle as it blew the v8 and was unusable - so I’m not looking a gift horse in the mouth!

 

Whenever I take on a project I try to pick up new skills - this time around it’s basic metal fabrication and welding. I have a very basic garage set up with a railway track anvil, a couple of vices, a bench mounted metal brake, an old guillotine and a nice new MIG welder. I’ve been putting off the front bend panels - it’s pretty simple for most out there, but for me it’s three connected panels that I want to look as factory as possible. Anyway, I have repaired the top panel where the bonnet/hood latch mounts and today I put in a radiator side panel which contained folds to strengthen it. I have two lateral lower panels to do next. I know the panels will be out of sight…. But I will know if they are a dogs breakfast!

 

 

 

 

[nevdrum]

Offside rad support done (last post). Now bottom lateral support done. Not factory but serviceable (I’m learning!). Top face of lateral support hopefully tomorrow.

 

 

[nevdrum]

Front sheet metal reinstated. Not really happy with my pattern making, as not quite symmetrical but it will be hidden behind grill. First picture shows pickup as bought with cut out viable in front bib/grill area. However I have more confidence now with thin panel welding, so this should pay off with the few panel repairs I need to do. 
 

 

 

 

[nevdrum]

Put the tray back on today. No diff in yet, but the rear is sitting very high - think it will be custom rear coilovers. Very happy with how wheels sit in the arches and their spacing in terms of track width with the existing arches.

 

 

 

 

[Satisaii]

I don't know what coilovers you have, but I would try some helper springs to get the vehicle lower.  The Miata rates are not going to be right for the truck anyways.

 

Watch for axle to spring / perch clearance in the rear, and for the fit through the upper control arm triangle in the front.

 

Maybe some 2" 100lb springs with couplers to start.

 

I am doing a similar build, but have not updated my thread in a long time.  Still working on it though.  Yours looks better, and you have better fabrications skills than I do.

[nevdrum]

9 hours ago, Satisaii said:

I don't know what coilovers you have, but I would try some helper springs to get the vehicle lower.  The Miata rates are not going to be right for the truck anyways.

 

Watch for axle to spring / perch clearance in the rear, and for the fit through the upper control arm triangle in the front.

 

Maybe some 2" 100lb springs with couplers to start.

 

I am doing a similar build, but have not updated my thread in a long time.  Still working on it though.  Yours looks better, and you have better fabrications skills than I do.

Hi. What’s your build thread called? The overall weight is very similar to miata/mx5 (940kg vs 960 kg). I won’t be using pick up for heavy duty work - just push bikes and small tip runs. 

[Satisaii]

Popcorn is the name of the thread.  Turbo + E85 = Popcorn

 

I have not put my truck on the scales to check the weight distribution recently.  I think the rear is going to be lighter than a MX5, but I could be wrong.

 

We run helper springs on all of our coilover shocks.  They allow for a higher main rate to control body motions, more shock travel, lower ride height, and a better ride when transitioning from droop to bump.

 

Are you trying to match the OEM ride height of the MX5?  i.e., using stock length shocks?

[nevdrum]

I read ur thread - nice! I like the design work it’s much more thorough than my effort. I’m trying to have a nice stance, but it will be lower than mx5 OEM. My rear suspension top mount is about an inch lower than stock. I have Meister R Sportives at the moment, but I think I can get fully adjustable coil overs than will have more adjustment range. I agree the back is lighter than mx5 so I may wind the spring base down to help reduce height. In the end, we have Gaz in the UK who will make to order - I’m sure with all the hatchbacks around with limited suspension travel I will be able to so quite easily. I went for the strut mounts slightly lower so the mounting plate was supported by the chassis rail. Not really very scientific, but I figured I could accept a shorter travel coilover given the lighter rear end. 

[projectrally]

Any progress?

[nevdrum]

Apologies to everybody in Ratsunland. I went to NZ for a family trip, and since return I’ve been getting my house ready for sale. I will be moving in August. 
 

however, I found time today to get the engine mounted. I still have to remove and relocate a chassis crossmember, as it sits right where the gearbox mount wants to go (see pic of raised gearbox sitting on crossmember). Good news is the engine will sit nicely and a can use a MX5/Miata Mk1 NA gearbox with the gear shifter modified to sit further forward. I’m also hoping to secure a Datsun 620 bench seat as this has a cut out for the shifter. 
 

Edited April 21, 2025 by nevdrum
Correct spelling

[nevdrum]

MX5 1.8 VVT engine - approx 145bhp (original 520 power 68 bhp)

 

 

currently installed with a MX5 Mk2 NB 5 speed gearbox. NA gearbox is same but has different shifter which can be moved forward about 4 inches

 

 

Intend to use a Datsun 620 bench seat for the gear shifter cut out: 

 

 

[nevdrum]

Been busy lately with work and getting house ready to sell. Back on the 520 this weekend. I had decided to keep standard engine mounts and move a chassis cross member back about 2-3 inches in order to clear and mount gearbox. Cut the cross member out (it’s one of two) and widened it as the chassis splays outwards as you move towards the back. Half welded it back in today. Chassis is way more rigid than before as a welded in front subframe now sits where a bolt on brace was for the old front suspension, and the rear subframe acts as  another double crossmember. A removable gearbox mount/crossmember will also go where the moved crossmember used to be - I will support the gearbox at two points. All this work makes the ute moveable as a unit with the gearbox/engine in it. I can also mount the diff, double check alignment and get the prop shaft made up. Firewall and inner wings after and that should be the last of the major works.
 

 

 

 

 

[nevdrum]

Not much doing this weekend. I did do a trial paint of the dash - as I will fit it soon to determine the position of the cross brace needed to mount mx5 steering column. Also a bit of a look at the results I will get from my home painting set up.