(Unofficial) Project MX720 Build Thread

[petercscherer]

I've already posted the majority of my initial work on this 1982 Datsun 720 in that specific forum section: http://community.ratsun.net/topic/65349-project-720z-1982-datsun-720-sport-truck/ But I thought I would post updates and hopefully get some feedback here in Project Datto. 

 

I've taken a page from Bob3 with my engine choice and picked up a 1997 Mazda Miata 1.8L drivetrain to do a basic engine-swap into my truck. You're probably wondering why I'm not going KA, SR, or CA.... Well, let me explain:

1.) A 1.8L Mazda Miata 4 cylinder puts out 135hp stock with potential for much more.

2.) There's a huge aftermarket for the Miata drivetrain, which should make upgrades easier to plan-out.

3.) Miata engines are already rear-sump oil pans, so there's no need to modify it like a KA or SR requires.

4.) The Miata 1.8L is incredibly light and compact.

5.) I've spent the past 3 years driving NA Miatas and I've become accustomed with their mechanicals and aftermarket.

6.) The Miata transmission is one of the best in the industry and has perhaps the smoothest and shortest throw of any Japanese 5-speed.

7.) I'm the kind of guy who wants to be different. 


So here's what I started with:
 

 

Here's the results of about 8 months of driving, upgrading, and personalizing:

 

Just a stock Z22 with a Weber upgrade and some Pacesetter headers, but nothing too exciting or modern. That's where the wonders of the internet come in:

 

Teardown of what was "supposedly" a clean JDM-spec engine began:

 

Milky oil gave me a sinking sensation that I was in for trouble... Luckily, it was just a warped head causing a water leak into the oil passages and I easily sourced a rebuilt head for a very reasonable cost.

After installing all new components and degreasing, it was paint-time! I've always liked the Burnt Copper tones and this color specifically came from VHT. 

 

 

Going forward into the assembly process, it was like building a 1:1 scale model car, everything just goes into place and there are very handy instructions in the FSM. 

Capped off with the shaved and painted cam cover. 

 

 

I decided to forge a new path and get some decals made-up to further disguise the motor:

 

I picked up the best header for swapping into the truck, this way I don't run into any steering shaft or frame-rail clearance issues.

Oh, that was the moment when I knew I was smitten...

 

 

Here's the complete drivetrain mocked in place: 

 

 

I still have a lot of work ahead of me; wiring will be the huge hurdle in the coming weeks, but I've gotten a great project plan all laid out to get this completed in the next few months...

 

I just wrapped up a full 2.5" exhaust system that runs as a single to the back of the cab and then splits into duals that exit on either side of the stock license plate mount.

 

 

I just want to make clear at this moment: I actually didn't have to do much to install this into the truck! Other than welding in new engine and transmission mounts, the drivetrain fits in like a glove! Even the new Miata 5-speed shifter comes out in the same hole as the original Datsun shifter. 

I'll be trying to update this thread as I move forward, and I'll try and grab photos where I can to help keep the posts lively. 

~Peter

[flatcat19]

Sweet. Watching. 

[Rhapakatui]

I'm glad you made a build thread.  If I'd seen this truck in person without having seen this thread, I would've spent way to long scratching my head trying to figure out what engine that is.

 

It looks great in there.

[Bob3]

Looks great!  :thumbup:

[teagueauto21]

Hell yeah! Ill most definitely be watching this one for sure!

[Draker]

Sick! ... 

 

How is the cost of the Miata engine vs. SR?

 

And why JDM?

[petercscherer]

 

 

How is the cost of the Miata engine vs. SR?

 

And why JDM?

Well, JDM engines can be purchased through engine-importers for far less than finding a donor-car locally. The engine/transmission was $600 delivered, which is far cheaper than any decent Miata in the area. Even a high-mileage 1.8L Miata here in Texas is $2500-4000...

 

So Miata vs SR: way cheaper. Miata vs KA: probably even...

 

~Peter

[Draker]

Damn.. not bad. 

[ArchetypeDatsun]

Love it definitely keeping tabs on this build.

[petercscherer]

Wrapped up my motor mounts tonight:

 

 

 

Had to take a few months off due to surgery and recovery-time... So I'm just now getting back into the shop. I'll be updating this nearly daily, so I'm thinking this is really going to work! :D

~Peter

[Lockleaf]

Looks like it fits nice. Did you build solid mounts or is there a bushing in there?

[datzenmike]

Got a picture of the transmission?

[petercscherer]

Looks like it fits nice. Did you build solid mounts or is there a bushing in there?

There's a bushing in there; I modified a set of mounts for Big-Block Chevrolet V8 motors... Actually made for a very easy install. 

[petercscherer]

Got a picture of the transmission?

Odd, actually I don't really. I'll be working with the transmission mount tomorrow, so I'll get some pics then. Here's what I have now.

[petercscherer]

Update: 

Finished up the transmission mounts!

 

So, it's finally back together...

 

 

Cab-side of the transmission:

 

Custom cold-air-box sits where the Z22 dual-coils sat before:

 

It's tighter than I'd like, but I hate to cut virgin firewalls...

 

 

The Datsun 720 heater hoses come out of the passenger side, and the Miata engine hoses are on the driver side... SOOOOO... Had to use some U-bends to get everything in the right direction.

 

 

Due to space, I'll be using a VW Scirocco radiator, which puts the intake/exit hoses on the same side, which is what the Miata engine required. Fabricated some mounts and got it as far forward as possible to maximize engine space.

 

 

 

 

So, after far too long, I've gone from this:

 

To this:

 

Still wrapping up the exhaust today, so may get some pics of that assembly installed...

 

Laters, 

Peter

[Lockleaf]

Very nice.

[petercscherer]

Finished the exhaust (for now...), it's not pretty, but it will work while I get the engine started and dialed-in. Again, the idea with the exhaust being in flanged sections is that I can replace sections based on how loud or quiet I want the truck to be in the end. I still have a bin full of exhaust tubing and mufflers to test!

 

 

Hangs lower than I'd like, but that's what happens when you run 2.5" exhaust...

 

Not a bad looking a**!

 

 

Next up will be the beginning of the wiring nightmare; not really looking forward to this part. :/

~Peter

[flatcat19]

Dude! Great work.

[Bob3]

Great Job!

[mrbigtanker]

Very nice set up you got there..

[petercscherer]

As I begin the process of wiring and such, I decided to first figure out where to mount my MegaSquirt-PlugNPlay ECU; I finally settled on a bracket in the center console, where it'll be easy to hide, and also make plugging in my laptop much easier on the go. I'm using a 1983 KingCab center console, which actually fits in quite nicely! I'll be making the old "DATSUN" cover fit over the hole where the ECU plugs are right now, just to hide it all better.

 

 

Might be a few days until I get another update posted, I'll need to figure out what parts of the Miata harness even matter right now, and try and get things down to the bare minimum...

 

~Peter

[hobospyder]

hey i have that same screwdriver. it's on top of my fridge though

[Draker]

Not only is it nice work.. but quick work as well.

[Jester]

hey i have that same screwdriver. it's on top of my fridge though

 

:rofl:  :rofl:  :rofl:  :rofl:  You crack me up man.

 

Great build thus far. Keep it up man.

 

You know, I hear Bob is pretty good at wiring Miatas. 

[hobospyder]

What? I had to fix my freezer ice thingies. Probably broke it completely but hey, I tried.

 

 

Keep driving in peter, this is an interesting build and I'm enjoying watching