The SA22C uses a steering box with Pitman arm, idler arm and center link rather than a rack and pinion system like every other car I have owned.  The steering box has caused clearance problems in the past, but I have decided to stick with it.

In this entry, I am going to give details of the center link that might be useful for other first generation RX-7 owners who are looking to swap steering systems or parts.

Pitman Arm to Idler Arm – 26.625″

Tie Rod Mounting Holes Width – 23.1875″

I have been unable to determine the type of taper in any of the holes.  If you have a way to do that or already know, please post it in the comment box at the bottom of this post.  The Pitman arm and idler arm are different sizes, probably so that the center link cannot be installed backwards.  Unlike GM and thus circle track steering systems, the SA22C steering setup puts the tapered studs on the idler and Pitman arms, not the center link.

I am not going to use the OE tie rod ends since the threads are metric and will not easily interface with the available tubing or rod ends I need to connect to the stock car spindles.  The tie rod mounting hole is already larger than ½” at its largest point, so I will have to drill them out to 5/8″, the next commonly available size rod end.  Fortunately, the 5/8″ rod end is a common size for circle track steering systems, so I won’t have to fabricate anything special once the factory tie rod mounting holes in the center link are drilled out to the proper size.  As the center link is almost ¾” thick and made from high quality forged steel (I think) this could be easier said than done.

My center link has seen some hard use and there were a couple of dings as you can see above.  I decided to get rid of them even though  I don’t think any of them would have an impact on performance.  10 minutes with the grinder got rid of the lumps.

Good as new.  Time to drill out the holes, paint it up and mount it in the car.

The RX-7 uses a conventional, production style front sway bar that connections to the chassis next to the tension rod mounts and then to the lower control arm. There is absolutely nothing wrong with this setup, and ones that are similar in execution are used on production based race cars the world over.

This is the stock bar. My son is helping me measure it.

However, since I had determined that the factory front suspension design would be completely eliminated, I felt like designing around an OE sway bar might become more of a liability than it was worth. So, like the SLA project, I cracked open the circle track parts catalogs and started cruising eBay for bargains.

Before I go on to the planning of the front sway bar project, I will share the dimensions of the stock unit for those that need them. Also, the replacement will need to be approximately the same since I am retaining the front strut rod (tension rod) style setup and (preliminarily) plan to locate the new sway bar in the same general area and fashion.

Inner width:

Outer width: (picture of what this is measuring is the one with my son in it, above)

Arm Length:

Arm Offset:

Next up, the plan for the replacement.

Assessment of the steering system of the Mongrel was one of the toughest parts of the project because, looking at it, the system seemed like a relic of a bygone era. The truth is I have never owned a car that wasn’t equipped with rack-and-pinion, so to find myself confronted with the reportedly inferior the parallelogram system was an unpleasant surprise. Furthermore, internet research revealed a pervading opinion that the RX-7 execution of this system was less than optimal.

Those people who know me and even those who have just read this blog before probably sense another major redesign project coming on. Well, I am sure to everyone’s surprise including my own, that isn’t the case here. Assessment of the steering system came down not the design of the steering itself, nor any inherent weakness thereof, but to the space that it would occupy.

Exhibit A: The Steering Box

The steering box caused no end of frustration when trying to fit the engine. One would think that this would lead me to the path of replacing it, however, for once, it did not. There are many SA22Cs with Ford Windsor small blocks in them, so I knew that it could be made to fit. Looking in the junkyards, the RX-7 steering box was one of the most compact I could find. Any possible swap would make the situation worse, not better.

Exhibit B: The Center Link Path

The center link (the part that connects the steering box to the tie-rods) has to pass through the rather narrow passage between the silver oil pan, on the left and the black front subframe on the right. Neither one of those two parts are particularly appealing to modify.

Here is a close-up shot where you can also make out the pitman arm on the steering box on the far (driver) side.

The alternative to the steering system on the Mongrel would be to adapt a rack-and-pinion unit from another car. Since it, like the center link, connects to the tie rods, the rack-and-pinion unit would have to occupy about the same location. The location above is smaller than the Focus SVT rack I have on hand.  Knowing that this would fit, I made the unprecedented decision to take the quick and easy way out.

A quick side note: those pictures are making me reconsider the wisdom of fitting a deep sump oil pan.

So, not through merit, assessment of the steering system concluded with the realization that it could well be about the only solution available to me at this time. One day, when everything else is running well, I will likely look for an upgrade, but at this point, the plan is to run it in as close to a stock configuration as possible.

I had originally planned to make my assessment of the factory front suspension piece by piece in order to inform readers on what basis the modification I chose were made. However that has become unnecessary. While this entry will cover some of the assessment information, the conclusions reached render the part-by-part format obsolete.

First, I bought Jim Susko’s excellent G-Force Engineering RX-7 tuning suspension tuning guide. If you have first generation RX-7 and are going to modify the suspension, buy this book. Even if you don’t follow his advice, you will gain a better understanding of the challenges you face.

What did I learn from the Susko book? The RX-7 strut front suspension is pretty miserable. Every strut suspension incorporates significant compromise, however the RX-7 front end seems to have done a worse than average job balancing them. There are plenty of books available that can do a much better job than I can of explaining what strut suspension lacks from a performance perspective, so if you don’t understand why struts are never going to be the best, I suggest you read one. Chassis Engineering by Herb Adams is a good one for both the beginner and more seasoned car enthusiast, in my opinion. But it was Jim’s in-depth review of the SA22C front suspension that made me realize that the front suspension was not going to be the way I wanted it as a result of simple bolt-on changes.

While G-Force offers solutions to many of these problems, , and many of them are beyond bolt-on, there are some problems that remain and others that I have no desire to spend the amount of money needed to overcome. The biggest problem is cost, but there are many others that linger even after spending thousands of dollars.

Problem 1:
As shown previously, the hub and rotor are one unit. This makes adding larger brakes more difficult and hampers serviceability.

Problem 2:
The struts are very small diameter, limiting the number of race valved units that can be used. Since the upright and spindle were made as one unit, rather than the more popular bolt-on style found on newer cars. My first thought, with the help of Scott Johnson, was to use the uprights from a mid-70s Toyota that is very similar in many regards, yet due to a larger ID strut tube, allows for a wider range of dampers.

Uprights: Mazda left, Toyota right.

An added bonus is that the Toyota uses a bolt on rotor.

The rotor still requires removal of the hub, but not its replacement during service.

The Toyota parts swap was looking promising. Even the hub height would be similar, eliminating the need for expensive custom wheels.

Again, Mazda left, Toyota right.

So what lead to the Toyota parts not being used? Spindle angle.

The angle between the two spindles relative to the vertical strut tubes is obvious in this photo.

The end result was that in order to run these Toyota parts in the SA22C, the camber plate would have to be so far inboard of the original location that adjustment would have been impossible without significant portions of the chassis being altered. If I am going to alter the chassis, it isn’t going to be to end up with another strut suspension. Nor am I willing to spend the money on custom strut housings.

Problem 3:
The hubs are saddled with yet another deficiency. Mazda saw fit to burden the SA22C with a peculiar 4 x 110mm bolt pattern that is used by no other vehicle. Seeing the error of their ways, they introduced the 13B powered GXL-SE with a 4 x 4.5″ (4 x 114.3mm) pattern. While these parts could offer a solution to this problem, they do nothing to address the others.

Quite literally, it was three strikes for the front suspension. The assessment was that since the easy and inexpensive Toyota parts swap hadn’t worked out, it was time to seek out a more aggressive solution – a custom double A-arm conversion.

The hood of the car may not seem like it is a big deal. After all, it is little more than a flat panel mounted on hinges. True enough, but when one is trying to put a V8 underneath a sloped hood like that found on an SA22C, things can get complicated quickly.

There are a number of compromises that surround the hood height. Since I am not running a tube frame front end (yet?), there is a fixed height that the engine must fit – the distance between the top of the front cross member and bottom of the hood. Given more money,a dry sump oil pan might have allowed for the engine to sit lower, but without that luxury, the height of the engine is variable only at the top.

On a V8, unlike and inline design, angling the block for reduced height and extra clearance isn’t an option. The solution is a shorter manifold, carburettor and air cleaner assembly. The problem is that all of those entail compromises to airflow and hence horsepower. Using a Weiand X-CELerator manifold I picked up used for $75, allows a minimum height due to the low profile, single plane design. Still, add in an air cleaner and a 4150 style carb, and the familiar problem of two things trying to occupy the same space appears again.

Fortunately, I didn’t find this out the hard way, and knew it would be a problem. Here is quick glimpse of just how much clearance was needed for the solution that I would pursue.

While the dirt modified look is kind of cool, I think I can do better.

I must confess that I love gauges. Not only are they functional, but a full brace of gauges just gives any car an authentic performance look. A look that the stock gauges really cannot claim to have.

Actually, Mazda should be credited with what is actually a pretty function gauge selection, one that surpasses many modern cars. Add in the fact that the most important gauge, the tachometer, is large and in the very center shows a performance bent.

Be that as it may, there is considerable effort required to have those gauges work with the Ford engine and the result will be something less than awe inspiring. The work required to use the stock gauges is clearly not worth the return, so they are in the box of parts available to the first person willing to flash me some money.

The plan was originally to use the stock RX-7 rear axle with whatever needed to make it work how I want. As stated in Assessment – Driveline – Rear Axle Location, the factory Watts linkage leaves something to be desired. Add in the fact that the upper arms are not a good idea and the rear brakes are nothing but scrap metal and the rear axle housing quickly become little more than a shell to be used as a blank canvas.

The suspension parts will be covered in their respective sections, this entry will cover the differential and the axles. The live axle of the SA22C gets the following glowing review from Granny’s

“Mazda planned accordingly, and designed plenty of strength into the RX-7’s rear differential/axles/and hubs. Experience has shown that the stock NA RX-7 components are strong enough to withstand low 10sec 1/4mi passes, a feat that requires around 500hp.”*

It should take me more than a couple of years to feel the need for 500 hp, so I thought I would be OK. However, a little more digging lead me to Mazspeed and specifically, their piece on the rear axle.

Since I have a 1979 car, if I have the original axle, the Mazspeed axle link says “the axle assembly used in 79-80 models cannot be altered to add a limited slip differential. Treat these units as really big paperweights or one more thing to clutter up your garage.” Great. Of course, upon disassembly, I found out that I have a 4.875:1 ratio and limited slip. If it is a later axle, someone put a lot of money into a drum brake rear end which makes no sense.

The parts are in good condition, the question is what to do? Axle swaps aren’t exactly rocket science, and while the 4.875:1 ratio with certain pin me back in the seat, it isn’t really an optimal gear for track use. Plus, in the Miata, the same differential isn’t considered hardy enough for a V8 swap. How much difference does IRS make to durability? I don’t know and I haven’t yet found anyone who does.

*Please note that I have since found the information regarding this axle to be contradicted by the experiences of some people. Rich, May 2008.

Good brakes always top my list of things I demand in a car. For reference, I made a brake upgrade for my Focus that uses 12.2” diameter 1.1” thick rotors mounted to aluminum hats, and then added calipers from a Mustang Cobra. When it comes to brakes, there is no point in messing around. It is no exaggeration to say that your life depends on your brakes, and running a car with as much power as this Mongrel will have, good brakes are mandatory.

It is common knowledge that brakes do not stop a car – tires do. A car can only stop as fast as the tires will allow. Once lockup (or if equipped, ABS activation) is present, more braking torque is irrelevant. Thus, using torque output as the main goal in designing a brake system is foolish. Inability to generate enough torque is rarely the biggest shortcoming of a brake system.

Where brakes generally fail is in their ability to perform repeated high torque stops. Heat buildup in the system leads to lack of torque, a soft pedal and increased stopping distances. This is usually referred to as fade. There are many ways to beat this, but I hold the opinion that the cornerstone of any high performance braking system is rotor mass. Mass is king. Large rotors capable of absorbing, dissipating and dispersing the heat of repeated high torque braking are required.

Which leads us to this:

The stock setup

Moving beyond the blatantly obvious problems of insufficient mass to stop a 200hp car, never mind one that will have 300 or more, the factory has presented some challenges. First, and most seriously, the rotor and front wheel bearing race seats are part of the same casting. Thus one cannot substitute another rotor without having to deal with the issues of perhaps also needing to change the bearings. This can be very difficult to do, as matching it to the spindle snout is required.

Currently, there are a few ideas designed to circumvent this problem that are under evaluation.
1. Machine the rotor down and then drill what is left to accommodate a bolt pattern that is used commonly on two piece hat and rotor combinations. 8 on 7” circle is common and may work. Problem is that the rotor is vented, and thus not just a plate that is easy to put holes in.
2. Update to 1984 or 1985 spindles that allow for easy adaptation of second generation RX-7 (FC3S) hubs. These hubs are not integral to the rotor and would allow for a more typical hat and rotor combination. Problem is the expense of the hubs and the fact that my bolt pattern will be changed. While I have no loyalty whatsoever to the esoteric 4×110 now on the Mongrel, I would have to consider buying new wheels and drilling the rear axle flanges in the cost scheme.
3. It was noted by my friend Scott Johnson that the spindles of his 1973 Celica are very similar to those on the RX-7. You can see what Scott did to his front suspension and the Celica uprights here. The Celica uses a hub that is not part of the rotor casting, but is complicated by the fact that it uses a plate to mount the rotor to the back of the hub rather than a hat. According to Scott, there are many years of Toyotas that could be adapted, so that could change. Making sure that balljoints will work and everything lines up is a big unknown. The known problem is again the bolt pattern. Toyotas, along with everyone manufacturer other than Mazda, never offered a 4×110.

The other serious problem with the rotor is the lack of clearance between it and the balljoints. This means that the mandatory extra width will have to be accommodated by the space on the outboard side. This pushes the outboard side of the caliper further into the wheel, causing clearance issues or a compromise in wheel offset. Nothing major, just another thing to that has to be accounted for.

Stock caliper, soon to be paperweight.

Fortunately, the caliper situation is somewhat easier as no part of the stock setup needs to be retained. Mazda uses a nice bracket that connects the caliper to the spindle. Since this bracket uses bolts on both ends, it is very easy to make a new one that will allow for the use of a different caliper. This makes fitment of a four-piston fixed caliper on any diameter rotor simple. The fixed caliper returns better pedal feel, superior wear due to less flex and, if the right caliper is selected, a huge array of racing pads at prices well below what a similar pad would cost for most any production caliper.

The difficulty is that the stock caliper piston is tiny. At about 39mm diameter, it simply does not have the area that most four piston calipers have. Normally, on a single piston caliper, the piston is large enough that finding a four piston caliper that is hydraulically equivalent is not that hard. Since the four piston caliper is fixed mount, the area of the single piston in the sliding caliper has to be equal to that of only two pistons. In terms of the Mongrel, the small factory piston means that the hydraulic system on the car will need serious evaluation before a caliper can be selected. That will be handled in Assessment – Brakes – Pedal & Hydraulics.

While some may find it odd that seats aren’t listed in an interior section, it was done intentionally. I feel that a seat is a very important part of the safety system of a car. Harnesses and roll cages don’t work without a seat that locates the driver properly.

Here is what occupies the front seat currently.

As you can see above, there is no driver seat and the car has a stock passenger seat. This leaves what to do wide open. The cage has an integrated seat mount and seat back brace. Because of this, I am leaning towards using an aluminum seat as those are far more adaptable to different mounts than composite seats. Please note, I am talking about an aluminum road racing seat, not a circle track style.

YES

NO

Go to Ultrashield to see where I got those pictures and there whole line up of seats. The reason to avoid the circle track style seat is the lack of shoulder support. Therein also lays the source of my greatest concern as I have broad shoulders for someone of my height. I will most likely have to test a number of seats before I find one that fits right.

The stock RX-7 comes equipped with a 55 amp alternator. According to Granny’s it is possible to adapt the RX-7 alternator to a 5.0 engine with very little effort. Since I have no RX-7 alternator, I don’t care.In order to make a plan, I will have to determine the electrical needs of the car and make sure that the unit can fit under the hood and on the engine. Since the 302 has been used in dozens of different cars, I imagine that this can be accomplished with a minimum of hassles and readily available junkyard parts. Since I got nothing to show at this point, here is my daughter being cute.