Nearly every sanctioning body requires a master cutoff switch – a single lever or button that will turn off the engine and isolate the battery from the rest of the electrical system.  While it can differ between sanctioning, many stipulate that the switch must be accessible by safety workers from outside the car and must act upon the positive circuit.

The only real complication involves an alternator.  Even with the power from the battery cut, if the engine is turning, the alternator will continue to supply unregulated voltage to the system.  This means that not only dies the switch not function as intended, but there is a risk of damage from voltage spikes.  The solution is a four post switch, which has the main circuit switched like every other, but also has an isolated circuit, activated by the same switch but getting direct battery power rather than feeding through the alternator.  These extra posts are for a circuit that will kill the engine.  I wired the ignition system power to the extra posts, and it works as intended.

What I came to realize was that with the switch accessible to the safety workers, it would likely be inaccessible to the driver.  I could put the switch near the driver side window, but all the power wires, the ignition system and the battery are on the other side.  Also, since in any sanctioned competition a window net will cover the driver side, a switch there might not be considered accessible from the outside.  Thus, the passenger side seemed the better choice, in spite of the driver access issue.

I still have to add the obligatory sticker that makes the switch location more easily known from the exterior.  However, it should be clear that the driver cannot reach the switch without climbing across the car.  Obviously when belted in, it just isn’t going to happen.  I decided that rather than add another switch, I would add a cable pull to the one already in place.

I used a universal parts-store sourced cable, originally purchased for the trunk release that I had section of leftover.  While it didn’t have a finished handle on either end, that didn’t seem like a huge hurdle to overcome.  The project would be a non-starter if there was not way to attach the cable to the switch, so that was step one.

A hole through the handle, a simple 10-32 Phillips head machine screw with a serrated face nut for extra security against loosening, then any unused portion of the screw cut flush with the nut and sanded smooth.  The cable is wrapped around the bolt, then pinched in place.  Pulling the other end of the cable is, by design, pulling the cable into the bolt.  Not too high tech, I will admit, but when it comes to an emergency use system, I am of the opinion that simplicity is a virtue.

Routing is accomplished with simple plastic cable clamps riveted in place.  The pull end would take the most work as everything would be fabricated from scratch.  I needed a bracket to hold everything near the driver and position the outer cable so that only the inner would move when the handle was pulled.  I needed a handle and way in which to attach the cable to it.  Finally, I needed to make sure the unit was the proper length and attach it.

The bracket was made from a three tabs I got from A&A Manufacturing.

3/16″ hole for use with rivets.  I added two more holes for strength when mounting, and made a duplicate for the underside.  This way the thicker metal plates sandwich the thin factory sheet metal and the rivets have strong material to grip.

With the base done, I took another of the same plates and bent it into a U shape in the vice.

That was done with a hammer, not a press or brake.  You don’t need special tools to do many things.

The parts were mocked up before welding just to make sure that there would be no problems with the rivet heads.  The hole in the vertical piece is for the cable to pass through.

This really isn’t my best welding work, to put it kindly.  The rods were damp and I was in too much of a rush.  The parts are held together properly, which is ultimately what matters, but I regret that it is so ugly.  The remedy was a nice thick coat of paint.

Spray on tool dip is a wonderful thing as not only does it cover the ugliness, but it also provides a nice, soft feel to the component; perfect for a part in the car’s interior.  I gave the backup plate a coat too so that it wouldn’t rust.

The handle is a universal lawn mower pull handle kit bought from my local Ace Hardware store then given a thick coat of red Plastic-Dip.  I put the pull string in a drawer for potential use later, then using the same bolted clamp method as on the switch, attached the cable to the metal insert inside the handle.  The holes the insert came with were designed for the pull string, so were much too large for the thin metal cable used in this project.

The handle end was finished by riveting the bracket in place, then adding the cable.  The two parts of the cable (inner and outer) were separated, the outer attached to the bracket, and then the inner snaked inside it.  The outer cable was secured to the bracket with a wing nut that I had in my bolt box that luckily had threads very close to the spiral of the outer cable.  The far side (not visible) has a crimp on connector to stop it from accidentally being pulled through the wrong way.  Even though there is little chance of that happening since the force is in the other direction, I like the added security.

That is the finished product.  I lubed the cable and tested it repeatedly.  Overall, it works nicely.  I found that the wing nut threads weren’t quite close enough and that with a really determined pull, the threads would slip and allow the outer cable to move.  I added some epoxy to area of the cable where the wing nut goes  and to the clamp on the other end just for extra piece of mind.  Total investment is under $10.  If you don’t have the leftover cable like I did, you might have to spend $20.  Still cheaper than another switch, not to mention running cables across the car to it.

I am starting to develop an appreciation for cables.  They are quite useful.

Two things done! We now have a warning light working as well. I am particularly pleased with the way that all the gauges look when the lights are on.

V8Mongrel.com has been quiet for a few days as I enjoyed the Memorial Day break. Before the holiday, Mike Westerfield came by for another evening of fun, powered up all the lights on the gauges and connected the oil pressure warning light to check to see if it would work as well. All that worked nicely, but we did find one problem.

The voltmeter reads over 18 volts when it is fed just 12. I bought the gauge used from Roush Racing, along with most of the others. They were takeoffs from an unknown car, which, one has to assume, was probably unusable for one reason or another. Chances are, the reason was a crash and that crash has jogged the gauge need from where it should be.

I got two oil temperature gauges in the package and one of them had the same problem. At room temperature, it would read about 170°. Obviously wrong. I found there was an easy solution for mechanical gauges such as this one. Simply prize off the gauge outer trim ring, remove the clear plastic face and then pull the needle off the pin. Do this with clean hands, as the special glowing paint on the needle comes off very easily if you have to wipe it clean. Then, boil some water, dump the gauge sender into it, and replace the needle so that it points at 210°. Be sure that the sender is immersed in the water, and not resting on the pot or container that is holding it.

For the voltmeter, it was harder to find the same known calibration point. Also, I wasn’t sure how the gauge worked. Was the input scale and needle movement linear? In other words, can I set it at 12v and know that it will be right at 13.7v or could there be another error? Mike has a variable voltage we can use to feed the gauge in order to check, and will bring it by in the future. In the meantime, we played around with using the 12v source from the battery charger, the same charger on the 6v setting, and then a 9v battery from a remote control toy car that was in the garage at the time to get more information. It seems like the linear fix will work, but once we get the variable voltage feed hooked up, we will know for sure. That should be happening by the end of the week.

The majority of the V8Mongrel project is focused on going fast and the work needed to accomplish that. In many ways, it is a race car, and most of the effort expended is on improving on-track performance potential. Yet the car has always been conceived as a street legal machine. Because of this, the interior will be required to make some concessions to civility that might otherwise not be found were it solely a track car.

One of these areas is carpet. Carpet is dead weight and a fire hazard in an all-out race car, nothing more. But in a car that will see street time, it is a critical element for comfort. Carpet absorbs noise, helps stabilize temperature and ties the look of an interior together. The carpet that came with Mongrel was pretty rough. It had been sliced somewhat mercilessly to accommodate the roll cage and looks not a day less than its almost 30 year age.

Fortunately, the RX-7 has a strong aftermarket which offers fitted carpet sets. Custom fitting a carpet is not something I wanted to undertake. Looking through various catalogs, I was shocked to find that the cost of carpet kits could be up to $300! Luckily I found the Auto Carpet eBay Store with a closeout RX-7 carpet kit for just $60. Only catch was that it would be maroon rather than black like the original. No big deal as the car is read and black is usually hot.

As they are in North Carolina, the carpet arrived in a day of winning it on eBay. The USA made carpet seems quite strong and the color isn’t too distracting. In fact, it has grown on me since it arrived.

The carpet also has a nice, large heal pad to help slow down wear in the most used area. Fitting the carpet will be one of the last parts of the project, so, for now, it is living inside the house, away from dirt, grease and sparks.

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.