LS3 into a 2004 Miata

Ever wonder how we build one of our LS3-powered Miatas at Flyin' Miata? I'll let you watch over our shoulders for this one.

The patient is a 2004 Mazdaspeed Miata. The Mazdaspeed is the preferred car of our customers for this modification because it has a nice interior and exterior. The fact that it's a Mazdaspeed makes no real difference to us, although the NB models have a bit more room in the engine bay and the 2001+ cars all share the stiffest chassis design.

We're going to install a crate LS3, an engine that could have possibly spent its life under the hood of a 2012 Corvette were it not for a wrong turn on the production line. It's mated to a T56 6-speed transmission and a Getrag differential from a Cadillac CTS-V takes care of power distribution.

But first, we need to get rid of the Mazda drivetrain. It's in our way. The easiest way to do this is the same way the car is built - we lift the body right off the drivetrain. We call it the "rollerskate".

Basically, everything ahead of the rear bulkhead or accessible from underneath is removed. This part happens pretty quickly.

With the car stripped, we start with the modifications to the shell. The transmission tunnel has to be slightly reshaped, and these two braces need to come off in order for that to be possible. We'll put them back in later.

The interior, ready for modification.

In the engine bay and transmission tunnel, we clean up all the affected seams. This makes it a lot easier to weld up again later and also makes for a cleaner cut with the plasma cutter. We've cut these with angle grinders in the past as well, but plasma cutters rock.

The biggest cut is this angle at the edge of the firewall.

After cutting, we weld in a reinforcement plate. A similar modification is made on the other side of the engine bay. The tunnel has also been modified in this picture, we cut a slot in it and use a knockrometer to move the metal outboard by an inch or two. Then we weld it back up.

The last step is to shoot some seam sealer over the seams then spray some body color paint over top.

Subscribed.

In for more! :)

We use a custom-built oil pan for this application. You can use a modified 4th gen F-body pan, but they're known for poor oil control so it's not the best option. Because the front of the pan is quite shallow, the stock Corvette windage tray needs a bit of surgery.

Bolting the pan on!

Time to assemble the drivetrain for a test fit. As I mentioned, it's a T56 trans getting plugged on the back there. We can do a T5, but strength is a concern as is the shifter location.

Here's the engine sitting in the tubular subframe. You can see our stainless exhaust system - it's a pretty tight fit in there, so we can't use off-the-shelf parts. We also have a stainless heat shield on top of the motor mount (visible just behind the AC compressor) and have to use a specific starter to give the clearance we need. Still, it's all servicable when it's installed - the plugs can be easily changed and it's pretty straightforward to pull the headers off.

The first drivetrain test fit. Slowly, slowly...

It's only temporary - we're checking exhaust fit and a few other things - but the engine is in!

Liking what I'm seeing.

This the sort of thing that would convince me to do this sort of thing. Carry on!

We're caught up with the work, so the pace is going to slow down a bit soon Let me know if there's anything in particular you want to see.

We do publish an instruction manual for this job, by the way. http://www.flyinmiata.com/support/instructions/V8%20conversion%20instructions.pdf

Why a T56 over the newer TR6060 version?

In large part because the TR6060 came out after we had done the engineering to fit the T56. We don't need the extra strength and the packaging of the T56 is almost perfect - the shifter ends up in the OE location.

Is the TR6060 the same as the Magnum? The Magnum presents difficulties in the shifter location compared to the T56.

What is the cost of a packaged car Keith?

IIRC, the TR6060 is just the upgraded version of the T56 (think T-10 and Super T-10) and is available with multiple shifter locations. The Magnum is the aftermarket direct version of the TR6060 (so they are essentially identical). It has triple synchros vs double, stronger gears, a 1-piece mainshaft, and a ton of other improvements. It shifts way, way nicer than a stock T56. The TR6060 is also setup to be compatible with multi-plate clutches, stock. With the T56 being out of production and you guys using crate new LS3's I kind of figured the trans would be the same story.

So yes, the Magnum may have shifter difficulties, but a TR6060 may not. Might be worth looking into.

We've got a stockpile of T56s at the moment, but it's good to know about the differences between the Magnum and the TR6060. Strength is not an issue at the moment, but we are concerned with future availability.

Does anyone have a confirmed measurement for the bellhousing-shifter distance on a TR6060? I found one crude diagram on LS1tech.com, but the author mentions that he found the bellhousing to be 3/4" shorter than other reports. And comparing to a T56, the shifter is 3/4" further forward.

AussieMG, the total price depends on the options chosen. This particular build is on the low end of the scale. We have an online configurator, but basically they start at about $35,000.

Keith wrote: Does anyone have a confirmed measurement for the bellhousing-shifter distance on a TR6060?

From what I've found, that is different depending on the application (Camaro SS, Caddy CTS-V, Mustang GT/Boss 302, Shelby GT500, Challenger R/T / SRT8, etc, etc). If the original T56 placement is what you are after, I'd look to the Caddy first, as it was the only one of those that started life with the T56 on the floorpan it's using now, though the Camaro is just a GTO underneath so it may work as well. I've also heard that the rare as hen's teeth G8 GXP used the TR6060, and that was a GTO floorpan as well.

The original Cadillac shifter location (with the T56) is not good for our application, so the TR6060 version would likely not be either. We need the shortest possible measurement, the furthest forward the shifter can be. Our cars are significantly smaller than most of the ones that use these transmission. The GTO is closer. The fourth-gen F-body is our goal.

T-56 dimensions and shifter locations

Here's the Camaro TR6060, by the way. According to this, the shift lever ends up 3.5" further back. Not cool. I think I've figured out some of the conflicting information I've found online, it looks as if the shifter itself is moved forward by about 9" and then there's an external shift mechanism. I need to get one of these in my hands.

The GTO and f-body shifter should interchange, that's supposed to be the only difference in those transmissions. The GTO shifter is just a rearward extension arm built into the shifter casing.

Yes, that's true in the case of the T56. Fitting the T56 is not a problem. I'm trying to find info on the TR6060. Has anybody got one?

I'm really disappointed no one here has asked this yet - what's the cost for all the good Mazdaspeed bits you guys pull off??? Any super-special package GRM discount there?

Price on application - there are a lot of different bits that come off. This car will likely supply a transmission and differential to an MGA that runs a supercharged Miata drivetrain/suspension and just trashed a 5-speed. More on that some other time...

Free shipping to all GRM members who pick up the parts at our shop!

Keith wrote: Free shipping to all GRM members who pick up the parts at our shop!

You are so generous!

Keith wrote: ...an MGA that runs a supercharged Miata drivetrain/suspension and just trashed a 5-speed. More on that some other time...

Yes, please!

Also, <3 this swap thread.

Carry on.

I finally have a goal in life: I want to own one of these before I die.

Before the big noisy parts go back in, we spend a bit of time laying down some sound and heat insulation. It's Cool-It from Thermo Tec. We'll cover the floorboards, transmission tunnel, rear bulkhead and trunk with the stuff. A heat gun helps a lot to make it conform well.

In the trunk, we've also mounted a bigger battery. It's the same unit you'd use in a stock LS3 Corvette.

The interior is stored off to one side while all these shenanigans are taking place. If you're doing this at home, make sure you label everything really well.

I love this.

[Ross is counting his nickels...]