Most difficult part of conversion ?

People always ask me what was the most difficult part of the conversion. For me it was the time spent on the gearbox. I had read all the comments on the forum about how to do the mod. The easiest part of course is switching the tailpiece from the 12A gearbox. The more difficult part is cutting the gear selector rod to fit and redrilling the hole. There is no room for error here. Cut the shaft too short and you can't select 2nd 4th or reverse. Cut it too long and you can't get 1st, 3rd or 5th (but at least you can cut it shorter !). Then there is the hole. Cut at the wrong angle and you're not going to get some gears. And you have to half assemble the box to test ! Yes...I messed up the first shaft. So then I only had one shaft left. I took my time and was so thankful when I could select all gears ! Then slowly put the box together taking care to seal all the joints. Looking back the only regret I have is not replacing the front and rear seals on that box. I'm sure I have a leak. It was such a simple upgrade to do especially since the box is 15 years old as well.

Other upgrades

Given that the car is 25 years old this year and that it has had an engine upgrade resulting in more than double the power now being produced compared to when it came from the factory, I have given some attention to the rest of the car, specifically the suspension/steering/braking systems. In terms of the braking system I removed all the disks and had them checked (yes, the rx7 released here in South Africa had rear disk brakes). The rear disks were still within spec so I had them skimmed. The fronts were too thin so I bought new ones. At the same time I also replaced all the pads. Now as some of you will know, there is a lot of parts one can inspect/replace when working with the front discs as the bearings are an integral part of the hub. So yes, while I was there I replaced the wheel bearings and seals. At the same time, I now had access to suspension and steering parts. First to go were in were poly bushings for the front anti roll bar. Ball joint boots were broken so those were replaced as well. The rear wheel bearings were tricky. They are pressed onto the shafts. You have to take the shafts to a motor repair place where they have a press. These guys removed the old ones and press on the new ones in no time. After doing all this work, the rx7 handles beatifully and I feel a little more comfortable while driving knowing that all these parts have been replaced. I would recommend to anyone doing an engine swop on these cars to do what I have done above as the bare minimum. Don't try and save money on not replacing your brake discs or wheel bearings or ball joints because you want to buy a fancy rev counter or 17" wheels first.

Video clip of a quick 'burn' down the highway

video clip of the rex on the highway. I just love the sound of the rotary with the Weber IDA. ENJOY !

Trip to the dyno

After about 1000km's of running in the engine, I took a trip to the dyno to get a reading. To refresh your memory, this is a s5 tii motor. The turbo has been removed. The motor was completely rebuilt and street ported for good measure. It has been fitted with a complete RB street system, as well as a weber 48 IDA.

On the first run we got a reading of 157hp(117kw) at the wheels. Not shooting the lights out but quite a respectable number.

I then consulted my engine builder and members on the rx7 forum. It was agreed that we would increase the size of the choke tubes and rejet the IDA for slightly less fuel and slightly more air.

The following weekend I was back at the dyno and the changes we had made resulted in an increase of 11hp (7%) to 168hp (125kw) at the wheels.

Here is a chart comparing the two runs :

Initial problems

As with all projects, there were some intial teething problems. The biggest one for me though was a vibration inside the car which I traced to the tranny mount. I had fabricated a mount but it clearly wasn't doing the job. I spent many hours under the car first trying to fit the second gen mount but then eventually settled on a modified first gen mount. Other problems included an oil leak aroound the oil metering pump and oil level sender areas. This was quickly resolved with the use of some sealant.

First start of the engine

Finally the day came when I had done all the preparatory work in order to start the engine. The car had been taken to an exhaust shop for the custom exhaust system to be fitted. The car was then again towed to a driveshaft shop for a custom driveshaft to be fitted. Those were the only two jobs that had to be outsourced. The rest of the work was done at home in my garage on weekends. The fuel system had been hooked up and all clamps was double checked. The radiator was installed and filled with coolant. The oil system was topped up and checked for leaks. All relevant wires were hooked up. The battery was charged and there was petrol in the tank. The engine and gearbox were earthed correctly. First turn of the key and all the red lights lit up on the dashboard and the Holley pump started whirring away. A good sign. Had a look at the fuel pressure gauge and a nice 4.5psi was being shown. Full turn of the key and up she fired first time ! I cannot explain in words what that sounded like. The next morning I fired her up again and recorded a small video clip. Here it is :

The engine as arrived !

Eventually the engine returned from the builder. I mated it to the tii gearbox and mounted it in the car. Here is a pic taken just after I had dropped it in.

The Racing Beat header can also be seen in this pic.