This is a post for some of the little things that currently sit at varying levels of completeness. Things that are not ready for their own posts, but still deserving of attention.

Firstly, some overall photos of the engine bay. You can see the custom coolant expansion tank that one of my racing buddies fabricated.

These holes allow cool air from the naturally pressurized cowl to flow into the passenger compartment.

Aluminium cover to prevent water from entering the vent holes.

Another aluminum cover to keep water out of the factory HVAC inlet.

The engine wire harness has been thinned. All unnecessary wires were removed. The wiring will get a dedicated post once it’s done.
This is the harness after I stripped the loom and electrical tape, and before I started removing wires.

The junk that I removed.

The harness, post thinning.

The harness reinstalled on the engine with nice wire loom.

The PCM was mounted in the passenger footwell via rubber vibration isolating mounts.

An aluminium shield protects the wires and connectors from unruly feet.

The factory crash beam was motivated to leave via sawzall. I did that to facilitate the removal and installation of the drietrain. I made a bolt in crash beam to put in its place. My structure seems to be of greater strength and since it bolts in, servicing the engine will be a breeze.

One of the best things about my new crash beam is that the OEM bumper beam fits snugly over it.

I needed more clearance between the front of the engine and the swaybar so I replaced the GTO harmonic balancer with the shallower CTS-V harmonic balancer. I now have ample clearance.

All of the old control arm bushings were removed via the Harbor Freight ball joint service tool. The ball joint tool made the job significantly easier. Stiffer urethane bushings will be going in their place once the arms are cleaned up and repainted.

The Canton Racing oil cooler was mounted. More on this later when I write a post on the oil system.

The Accusump oil pressure accumulator was mounted beneath the trunk pan.

The stout Getrag differential has been mounted to the Miata subframe.

It’s a big fellow.

A Walbro 255 fuel pump is now installed in the tank.

And there you have it–a shotgun progress update.

Pedals and brakes

We all know the importance of reliable brakes. When you push the stop pedal, the car better slow down. No exceptions, ever. Ensuring that that is the case involves more than having physically strong components. The components have to be appropriately sized for the application, must be able to dissipate a sufficient amount of heat, and the components also have to be appropriate for the temperatures that they will reach(i.e. a track car requires pads that can handle hotter temperateness than a street car). How much heat do brakes generate under hard stopping? Well, brakes work by using friction to resist movement. Friction is what warms your hands when you rub them together. Now imagine that your hands were rougher, you pushed them together with 4,000 pounds of force, and you rubbed them together at 112 feet per second. The cited force is an approximation of what will happen when I start to brake at the end of a 150mph straight–112 f/s is the speed of the outsides of the rotors relative to the calipers at 150mph. This is true for each corner in the front, and the numbers for the rears are about 20% of the numbers cited for the fronts. Your hands will not hold up to that and a lot of brake systems will not hold up to that either. Lots of heat is created, and the amount of energy that the brakes must absorb is exponentially proportional to the velocity of the vehicle. The heat is dealt with by using large vented rotors, using pads that retain their coefficient of friction under extreme conditions, and in some cases, by ducting air to the rotors for additional cooling. I’m doing the first two, and may have to do the last as well–time will tell.

Under heavy braking, a larger portion of the mass of the vehicle is over the front wheels. On a Miata with significant grip, the dynamic front weight bias could be as high as ~80% under heavy braking. This means that if you want to utilize all available grip to slow the car down, the brakes should have the same front bias as the dynamic front weight bias. That being said, it is common to give brakes additional front bias for the sake of safety. The car would have a tendency to spin out if the rear wheels locked up before the fronts, so brake systems are engineered to have the fronts lock up first. My brakes are no exception to this, however I am using a balance bar for fine control over front/rear bias. The balance bar will allow me to make adjustments to the bias, while strapped into my seat, to optimize the settings for the conditions that I am driving under. Other ways to adjust the bias are to adjust the caliper piston sizes, the number of pistons in the calipers, the diameter of the rotors, the diameter of the master cylinders, and the friction coefficient of the pads. These same things can be adjusted, as well as the pedal ratio(think mechanical leverage), to alter the amount of force the driver must exert to achieve the same outcome at the wheels. One thing to be mindful of is that nothing comes for free–if you have a pedal that requires little effort, that pedal will also have to be pushed further.

For the rotors and calipers, I chose to go with a proven setup. I got the Trackspeed Engineering front big brake kit and M-Tuned caliper spacers for the rear. The front setup includes 11.75″ Wilwood rotors and 4-piston Wilwood calipers. The pistons are 1.38″ in diameter. The kit also includes brackets and stainless steel lines that make these brakes plug and play. Trackspeed Engineering’s attention to detail manifests itself in things like safety wire to keep the bolts that connect the rotors to the top-hats from backing out. They also provide a good set of installation instructions. The stock rear calipers will be retained and spaced out further via brackets to allow clearance for 10.9″ sport rotors, which came on the Mazdaspeed Miata. Wilwood master cylinders were used for the brakes and clutch. I am not going to share the specifics there because my master cylinder choices, as well as the pedal ratios, have yet to be tested and proven. That said, my math indicates that there should be no issues. The pedals themselves are from a 2004 Pontiac GTO. They came with my drivetrain and have been modified to suit my application. The modifications included cutting and welding to alter the overall lengths and pivot points. The gas pedal was the simplest part, and minimal modification was necessary. I welded mounts into the car for the gas pedal to bolt onto, and added a point to the pedal assembly to provide the throttle cable with a place to attach in the new configuration.

In addition to greater capacity, these brakes weigh less than the stock components, and consumable items(pads and rotors) will last longer and are cheaper to replace.

Early stages of the pedal box. The balance bar is clearly visible here. The pivot point is adjustable so the forces applied to the front and rear master cylinders can be varied.

This is the finished pedal box.

The switch will operate the brake lights.

All three pedals can be operated as needed. The gas pedal was placed with heel-toe shifting in mind.

The plumbing still has to be done. Steel hard lines will be run through the interior to the front and back, and tee off at the ends to provide pressure to the calipers on both sides. The stock rear subframe comes with a tee fitting bolted to the passenger side. I relocated that to the drivers side to better accomodate my intended line routing.

Steering column become more….erect

I have done a number of things to this car to improve the static front/rear weight bias, and amongst them was moving the drivers seat as far back as it can possibly go. I made a new seat bracket early on that moved the seat back and optimized the positioning of my custom pedal assembly to work with the new seat position. The pedals, however, are not the only control that I need to be able to reach. The steering wheel needed to be about 6.5″ further back. A simple means of handling this is to make a steering wheel extender. To do that, I merged the base of the OEM wheel hub, which bolts to the steering column, to the front part of my Sparco steering wheel hub, which the wheel screws into, with a spacer in between. The base of the OEM hub and the front part of the Sparco hub are both made of mild steel, and I happened to have some scraps of 2.5″ exhaust tubing laying around. I cut the tubing to the correct length and welded the pieces together.

After optimizing the distance between the wheel and driver, I had to optimize the angle of the steering column because the extender alone placed the wheel up far too high–the top of the wheel obstructed my view out the windshield. This meant lengthening the mounts that hold the steering column to the dash bar, lowering the steering column itself. I ground off the old mount and welded my longer mounts in place.

Firstly, the OEM steering wheel hub resembles a slice of bread.

This photo illustrates the excessive angle that was present, placing the wheel too high, before I updated the steering column mounts to lower it.

After I adjusted the angle.

Optimal position is generally regarded as when you can rest the bottom of your wrist on top of the wheel without leaning forward. I’d say this is dead-on.

An exhaust system that the neighbors will love

There are a couple(two that I know of) aftermarket exhaust systems that companies have made for this particular swap. The available units are well constructed, however I thought that I could build an exhaust system that suited this car better, and do so for a fraction of the cost. So far, it is looking as though I have done just that. My top priorities for this exhaust system were performance and ground clearance. Performance is self explanatory. Ground clearance is also important because this car will be low to the ground and having various parts of it, namely the exhaust system, scrape the ground under certain conditions will make unfortunate noises and potentially cause damage. Stressing over the ground clearance of the exhaust system also provides more space for the addition of a full flat underbody, which has aerodynamic benefits, in the future.

I built this exhaust system from 2.5″ aluminized steel pipe. I chose aluminized steel because I can weld it with equipment that I already have and it provides some corrosion resistance. The pipes were cut by a chop saw with a friction blade. Mandrel bent tubes of two different radii and straight sections of pipe were purchased. Unnecessary bends were minimized for the sake of performance. The welds were intentionally made with a cooler setting than what would normally be advised. I did this to avoid excessive penetration, which would likely result in some extra turbulence in the pipes.

The shape of the system was chosen to maximize consistency between both banks of cylinders. Since the passenger side header lets out further forward than the drivers side header, and has a sharper bend to clear the starter motor, the x-pipe was placed closer to the passenger side to help even out the length of the two runs of pipe that lead to and from the x-pipe. The x-pipe is present to even out the pressure between the two sides of the exhaust system, allowing the system as a whole to be used more effectively. The x-pipe also results in a scavenging effect which helps exhaust gasses leave cylinders. A V8 engine has two banks of four cylinders. They fire at different times, and with each firing, a pulse, or pressure front/wave, passes through the exhaust system. Since the firing in the two banks is offset, an exhaust pulse from one bank flows downstream and reaches the x pipe when the valve, of the other cylinder bank, opens to expel combustion byproducts. (The time between those events depends on engine speed.) The effect of having a pulse from one bank enter the pipe for the other bank, via the x-pipe, is a vacuum which helps draw combustion byproducts out of the cylinder with an open exhaust valve in the adjacent cylinder bank. That increases efficiency and efficiency is the key to making power.

The system nicely tucks into the bottom of the car and does not have any apparent points of vulnerability.

The midsection of the system is supported by u-bolts which attach to steel braces that attach to the transmission side of the transmission mount. That way, vibrations are isolated from the chassis.

You may have noticed that this system lacks mufflers so far, or perhaps assumed that I do not value my sense of hearing. This car will not have much muffling, but it will have some so that myself and those around me can maintain some sanity. Magnaflow 6″ round mufflers are being used. They are about 20″ long and have a straight through design. They are not currently installed due to my running out of time, however they will simply be welded onto the end of what I have already made. I will trim the bumper cover more before I install the mufflers so that they can be mounted higher. I want to mount them as high as is reasonable to maximize the space left over for a rear diffuser, another aerodynamic downforce adder that I would like to make and install in the future.

Before trimming the bumper, the mufflers leave just enough clearance for a diffuser mounted at 10*. 7-10* is the commonly accepted sweet-spot.

This is roughly how the mufflers will look coming out of the back of the car. As previously stated, the bumper will be trimmed more and the mufflers will be mounted higher. I think they’re going to look great and sound even better than they look once I’m done.


This is how the exhaust system ended up looking. I added flanges, a pair of flex pipes to take stress off of the headers, oxygen sensors, and I reshaped the back passenger side of the system for additional clearance against the transmission tunnel. This piping, paired with my pair of Magnaflow mufflers, sounds really quite good. Many have complimented the sound, and I have also gotten quite a number of comments on how it’s surprisingly quiet. Win!

I welded some steel dowel to the mufflers so that they retain their positions relative to one another, and so that I can mount them to the chassis. Hard-mounting the mufflers to the chassis has proven to be an effective means of attachment, and I can get away with it since the flex sections prevent the headers from being stressed.

Radiator mounting

Seeing as this is a high-power car which will see track time, the cooling infrastructure needed to be updated. The radiator which I chose is considerably larger than the factory radiator, and the stock radiator mounts were removed to make clearance for the drivetrain to conveniently go in and out of the engine bay. Some new radiator mounts needed to be made. The design which I chose for the new mounts is simple, light, and very strong. The lower mounts, that the base of the radiator slips into, are much stronger than radiator mounts need to be. The mounts are overbuilt because they will double as mounting points for a belly pan and splitter. Once I dive into aerodynamics, this car will likely end up with a splitter capable of generating considerable downforce. The splitter and belly pan also need to be strong enough to not deform under small impacts. i.e. the car bottoming out over a tall speed bump or steep driveway. My lower radiator mounts should be more than up to the task.

These are the lower mounts. 1″ diameter 1/16″ wall steel tubing runs down from the frame rails and is held securely in position by gussets. The pockets were made from sheet metal.

This view is looking in from the opening in the front bumper. Sheet metal was used to create a surface for the radiator to lean against and more of that same material was used to triangulate those surfaces to the frame rails, adding significant strength.

Rubber bumpers were later installed on all of the mounts to isolate the radiator from potentially harmful vibrations. The radiator is slanted for three reasons. The first two are so that the mass of the radiator can be lower and further back. The last and perhaps most important reason is to create clearance for an air intake pipe to pass from the throttle body to the front bumper without having to cut a hole in the hood or use a smushed pipe.

What you have seen up until now allows the radiator to conveniently slide in and out of the car for the sake of easy serviceability. The radiator is also held in place by what are essentially L brackets that bolt into the frame rails and apply enough pressure to the back of the radiator to hold it securely.