In the last update, I shared the cooling system and a short video showing the car running. In order to prepare for the first street tuning session, I needed to get the car roadworthy. This meant that I needed to find a way to mount the battery, finish the intake/exhaust and figure out the gauges.
LS Swap FC RX-7 – Battery Tray
Something that is always a challenge when doing a swap is finding a spot for the battery. Many LSX-swapped FC RX-7 owners end up mounting the battery inside of the car. While this was an option, I needed to make sure that the car would easily pass tech inspection and I didn’t have lot of money leftover to buy an expensive battery. I wanted to use a common off-the-shelf battery that could still be replaced at any store that sold batteries. I had heard great things about Odyssey batteries, but finding a replacement locally if they go bad can be difficult.
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LS Swap FC RX-7 Cooling System
It’s no secret that LS engines have been swapped into RX-7’s for years. The benefit of being a fairly common swap is that there is quite a bit of information about how to construct an adequate cooling system. After doing some research, I discovered a company named Jags That Run sells a mount kit that utilizes a stock Corvette radiator. I found a good deal from a private seller of a brand new kit that had never been used. This was a great find since the kit sometimes takes some time to produce if bought new. I picked up an OE replacement radiator from Summit Racing and began the process of mounting it into the FC engine bay.
JTR provides excellent instructions with their kit that detail every aspect of the installation. The first step is cutting the old FC radiator support brackets. The stock sheet metal is bent in towards the center of the car and allow for the factory radiator to be mounted at an angle.
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In update 14, I went over the installation of the T56 transmission and driveshaft. Since the clutch slave cylinder is an internal type, it was installed during the clutch and transmission installation. To make the GM slave cylinder function correctly, a properly-sized clutch master cylinder must replace the stock FC clutch master cylinder.
LS Swap FC RX-7 Clutch Master Cylinder & Hydraulic Line
The best part about doing a fairly common swap is that a lot of the required research has been done already. A company named Hinson Super Cars produces various parts for LS-swapped vehicles. They are somewhat of an authority in the community and have been working with LS engines for years. For FC RX-7’s, they sell a modified Wilwood 7/8 brake master cylinder that is perfectly sized for the swap. To make it work in FC’s, they weld a metric threaded rod onto the Wilwood push rod. They also provide an adapter block to use the stock firewall mounting holes.
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The most difficult part to source for the swap up until this point has been the T56 transmission. T56 transmissions are typically found in LS1-powered Camaros and Firebirds (along with many other sports cars). They are a 6-speed manual transmission capable of handling over 450 lb-ft of torque in stock trim. Since so many cars are being swapped with LSX engines nowadays (including hot rods and other classic cars) they tend to be extremely sought after. Local sellers know the scarcity of them and try and charge a premium for high mileage used transmissions.
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In my last update, I showed the fuel system on the RX-7. In this post I'm going to go over nearly everything I have done to get to the point of starting the engine. It's going to be a big update and I guarantee it's been worth the wait!
With the engine sitting in the engine bay supported by the front mounts and a wooden block, Matt from Secondbolt Racing and I decided it was a good idea to start the engine to make sure there wasn't anything catastrophically wrong with it. Even though it had been inspected and everything looked fine, it wasn’t a bad idea to make sure it turned over and built oil pressure.
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Another area of an RX-7 that needs to be upgraded for an LSX engine is the fuel system. Even though the stock fuel pump is capable of flowing well enough for a stock engine, the pressure of the fuel needs to be regulated before it enters the fuel rails. I found a helpful post on NoRotors that explains how to remote mount a Corvette fuel filter in the rear of the car. This filter regulates the pressure at 58 psi (what stock engine requires). By placing the filter near the fuel pump, it frees up room in the engine bay and remains hidden in a relatively easy to access location.
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As I mentioned in Update 10, the Turbo II rear end was one of the most valuable pieces of the entire parts car. Instead of pulling the differential, axles, brakes and hubs and swapping them over to Project LSX-7, I decided to just use the entire Turbo II subframe. This made installation easier and since the parts car had nearly the same mileage as the shell, I wasn't too concerned about its structural integrity. Before I bolted the subframe up to the S5 chassis, I wanted to upgrade a few areas that nearly everyone who drag races these cars recommends.
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When swapping an LSX engine into an RX-7, the weakest link in the car is the stock differential. As with most manufacturers, Mazda didn't design their base model components to handle more torque than they would ever be exposed to. However, they did design the differentials in S4 Turbo II models to handle more torque since the engine produced significantly more power. Although some owners have gotten away with using an NA rear in their V8 swapped RX-7's, they typically don't last long after they start launching the car. The S4 Turbo II clutch type differential is known for its ability to take abuse and since it's a clutch type, it's also easier to rebuild.
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While it may appear that Project LSX-7 hasn't been touched in weeks, this couldn't be further from the truth. Before diving into the latest update, the first thing I would like to do is introduce Secondbolt Racing as the latest sponsor for the project. Secondbolt Racing was officially created 5 months ago by an Import Meet member by the name of Matt K. (v8rx7guy). Secondbolt Racing designs parts for late-model GM swapped vehicles as well as performing the swaps into import cars.
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When I was deciding on an engine swap, two of my deciding factors were ease of installation and cost. Right around the time I started to research potential swap options, a company named Ronin Speedworks released prototype photos of their FC RX-7 LSX mount kit. These photos helped make my decision a little easier.
Typically, swap kits for non-standard engine swaps can sell for over $1000. Ronin Speedworks sells their Supreme kit for $569 plus shipping. Their Supreme kit includes everything required to mount an LSX engine and T56 transmission (transmission mount not shown).
Since I wasn't too keen on designing my own mounts and these were so affordable, it was an easy choice. I purchased the complete kit and received it in less than a week. It was packaged well and everything arrived undamaged. The first thing I noticed when I unpacked the kit was the quality of the parts.
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