302 MX-5 - The Budget Daily Driver

I've worked on a bunch of different projects, from simple add ons to full on racecars (MX-5 + S2000 = MX200). Over the years I've gotten many ideas, but I've always been a fan of simple. After a bunch of thinking, I decided to do a carbed 302 MX5.

Seeing that I'm a student, I don't have too much money. The saving grace is I do automotive wiring in my free time for extra chedar. So sometimes I'm paid in cash, sometimes in car parts, and sometimes in food. Since I've had some pretty stable work, I began work on my new daily.

It starts with a 2001 MX-5 I got as a graduation gift. I drove it for a while, got a hard-dog roll bar and tracked it, then sold the motor and trans to raise funds for the build. The pictures are a little old, has sense had some one-on-one time with a truck on the passenger side, but it's the platform I got.

Once the motor was pulled out, we yanked the subframe and jigged it up. There are options out there for subframes, but when you have a machine shop in your garage.... why not melt metal. The subframe took a few forms. We tried to make it totally tubular, and it worked ok, but once we welded on the lower control arm tabs the subframe warped too much. So design number two used rectangular tube for the sides which made it a little easier to keep the shape. Don't have any pictures of the process, but here is the end result. Since this is the first MX-5 we've made a subframe for, there were a few hiccups. And the mig we used gave us issues at first. This took a little while to build. But in the end I'm happy with the result. Next one we build will have a lot a revisions, and will hopefully go a little better.

This is where we're at now (we = father-son project). Right now the car is on jack stands waiting for the new subframe. I've collected a set of FD and FC RX7 front calipers that I'll be working on retrofitting later. I also have a few jag rear ends (including a XJ-12 rear) and some Ford IRS 8.8s that I need to decide which I want to use. The motor has a Holley 600 4160 and a Edelbrock performer intake as of now. Still working on what I want to do for heads, but I got a set of GT40's that I can port match. Still working on ideas. First things first, we need to get the car back on the ground.

We also have a 1956 Studebaker truck that we are putting a 1969 454 and Hilborn stack injection that we are converting to EFI. If this thread does well and gives me some ideas, then I'll start a thread for my dad's toy. Oh, and we pulled a L67 a few weeks ago... I think we're addicted to projects...

Update: Here is a link to the Studebaker build!

coolio. i await more updates and details =)

4 projects is a OK start around here, but you will fit in just fine

Nice subframe BTW

SBF Mazdas rule, here's mine

http://s869.beta.photobucket.com/user/aussiesmg/media/RX50/MVI_0579.mp4.html?sort=3&o=18

In reply to aussiesmg:

Nice. I'm wiring in a turboed-sprayed LM7 into my buddy's FB. Really like those cars! And thanks, we worked pretty hard. Hopefully next time we do this we can improve on the subframe a little.

Well, today WAS supposed to be the day I get the miata back on the ground and cleaned up a little, but the something happened to the paint on the subframe and I had to sand black and respray it. Kind of a bummer, but something I can't let go. So here are a few pics of the poor car as it sits now.

Once it's cleaned up a little, I'll start getting ready to fit the motor. There is still some stuff I need to move around, and I need to go through the car's wiring to make sure it's good to go. More updates to come, hopefully next time they are of progress .

Took a little longer than I thought, but we finally got the subframe put in and the car is back on the ground and in the drive way!

We ended up installing some studs in the bottom of the car. They were easier to use than the bolts were, and we feel they work just as well. It took a little fitting, but that is to be expected. All in all, everything fits pretty good. Seeing that this is a beta, the next one we build will include a lot of improvements we thought of. I'm happy thou, and in the end, that's all that matters.

Now that it is in the driveway, I'll have a little bit of time to get the wiring worked out. Also, since it's been in my backyard for so many months, some critters have made their home in there. So I got to give her some love, but the next update is should be sooner than later.

Ok, so I spent some time today cleaning the miata up. Turns out that when you leave your car in the back yard for 6 months while getting it figured out, gets a little dirty. At one points ants made their home in it, and some roaches a little later. Inside of the car is now bug free! And I think she cleans up pretty good, if I do say so myself.

Most of the bugs were in the trunk, got that cleaned out and pulled the insulation out. Still have a long way to go to get it clean.

My top is going bad, leaks water into the trunk. Surface rust starting building up, mostly near the battery. Pulled the plug, cleaned it out some, and this is what I got.

I need to sand down the inside of the trunk, and paint it with something. What do you guys think? I don't think bed liner would be a bad idea. Maybe undercoating... I dunno, you'll never see it actually, it's all under carpet, but I need to protect the trunk from rust. And I need to figure out new sound deadening. Oh well, more updates to come!

Good stuff! Love seeing DIY examples of significant assemblies like subframes... Excellent way to make the chosen body and engine play nice...

Thanks! I'll get some picks of the finished subframe in the car when I have the chance. I didn't think to take any, was too excited when we got in installed and put on the ground.

Here is a link to the other car we're building, the 1956 Studebaker w/ 454 BBC

Just got back inside, it's a little cold for my taste but I've been chugging away out there. I started on the engine bay. Just locating wiring and labeling it so that when I go through it later on it will be a little easier. I want to relocate the main fuse block, probably inside somewhere. That or I will come up with a clever way of hiding it, but who knows. I've also taken some more pics of the subframe in the car.

As you can see, there is a lot of room to work with. My goal, in the end, will be to have all the wiring hidden. There won't be much to hide with the motor since I'm going carbed, to it seems fairly realistic. I'll have to spend more time figuring that out later thou.

On a side note, we picked up an E30 to put the L67 in, so that project will be posted one of these days. I promise, I was just walking down the road and there it was. I tried to tell it to 'get', but it kept following me home

And a little more progress before I called it a day. I move to the inside of the car and set up camp with my laptop. Went through the wiring manual, located all of the connectors, and labeled them. This did two things. It got me very familiar with the layout of the wiring, and now I don't have to look everything up when I want to know what a connector goes to.

I just have to pull the dash from out of storage and go through that, but I'll be stripping out all of the unused stuff here soon. I'll also have to figure out a few things, like how to get the A/C to work correct without the PCM. But all in all I'm happy with the amount of work I got done today.

Been very busy with school, couldn't work on the car but a little. I did, however, got some wiring done.

I relocated the fuse block to inside the car. I picked up some fuse blocks out of some camaro's, think I'll use those. They are short, narrow, and have enough fuse/relay connections. Also, it's side access, so I can easily put it on the passenger side floor under a plate.

Once I get some time (it's finals week soon) I plan on finishing this up, putting it all back in and testing it out. I also plan on using some bulk connectors for the parts of the harness that go into the engine bay. But more with that in the updates to come :-)

Been a while, eh? Well, school has been killing me, but I made some time. Now, let's get back to building this car!

I pulled the rear subframe today, I'll take some pictures tomorrow. Took some measurements, looking really good for the XJ12 rear end. I'm going to fab my own XJ subframe, but here are some numbers. The miata rear subframe is 34.5" wide with the mounting holes about 31" apart (measured in-between the holes). The XJ rear mounts the shocks 31" apart (measured from the outside of the bolt heads).

The XJ12 rear has a track of 58", the miata has a track of 56.3". I figure if I shorten each side by about an inch, I should be able to shoe horn everything in-between the mounting holes. My hopes for big rubber still live :-D and if I can figure out how to do this all right, then it should be fairy straight forward (relatively, of course). Could even tub the miata out, not go wide body and make this one hell of a sleeper... just a thought.

So this is what I got... well, not mine, but you get the idea.

I need to do more research as to what works best, but I plan on making something along these lines for the lower arm.

Jig the OEM arms, shift the jig back ~.85" then make the new arms. But as I stated before, I need to look on the forums and see what other people have done, what works, and what looks good on paper.

Once I have the arms, I can have the axles (more like drive shafts really) shortened as well. Rebuild the center section, brakes, e-brakes, get new rotors, shocks/springs. But one things at a time. The XJ rear also has what I'm assuming are torsion bars that come off the rear end that I will tie into the frame rails that are being installed hopefully in December.

As always, your input is always welcomed! I like new ideas and input. I will keep you guys posted as I progress this weekend.

I keep seeing XJ12 rear track widths all over the place... I think it's 61", but I need to keep looking.

Shortening driveshafts (axles in your case) is simple. So simple I wouldn't farm it out. If I see you this weekend I can show/tell you how I would do it.

Edit-hollow axles are easy, solid are best left for someone other than me.

Got some time between school and research to work on the car. The XJ rear is in, still needs some love. Next I get to make some faux suspension pieces and determine ride height. Good think I plan on running an 18 or 19, because with a 15 she sits LOW....

Definitely subscribed, I am planning on a 350 swap for a miata I just got.

Very cool. It looks good in there.

Remind me again why the Jag rear is a better option than the tried and true road blazed by Miata V8 crowd using the Ford and Getrag conversions?

I do get that the check to the Kit guys is about $3k all in; not cheap.

Is the Jag a more cost effective path? Shortening axles, fabricating new (shorter) control arms and predicting what the resulting geometry will do in transitoinal dynamic situations is beyond my abilities. Plus, for spares and repairs reasons, I try to avoid custom bits as much as possible.

Anyways..love the project, carry on!

What makes you want to use an XJ12 rear suspension instead of beefing up the Miata suspension?

Sorry for the last responses guys, been super busy! I work in an autonomous robotics lab at UF and we have a boat competition coming up in the first week of July (and we kinda sorta didn't start working on it until a few months ago). But I'm actually looking forward to having a few months that I can dedicate to this car, and hopefully have a motor in it by the end of the summer.

In response to some of the questions... I'm not sure if the jag rear would be any better than the tried and true options out there, but if we don't try something new we won't know what works. I liked how easy this rear end was to mount. I cut up the stock miata rear subframe, put some tube steel going across and welded in a support plate (and I now realize I did not take a picture of that!). Anyway, the XJ12 rear has a few things going for it. It's more or less a Dana unit, so I have access to some good parts. It's also IRS, which is desirable. To narrow the rear is very simple as well, still deciding how I want to do it. It can take some abuse, adds some weight to the rear, and the most important thing... it's really cool . It will be different, and that is the big thing for me.

I will try and get some time to take some pictures, write about where the miata is now and where I am going with it. A NA 302 is in line to be put in, but I may or may not have a black that is .020 over with TRW pistions and ARP hardware all over sooooooo..... here is a picture of the miata on the ground!

Very cool! Nice to see it progressing.

BTW, I have a big soldering gun I need to return to you.