I think I went a little more difficult route Tom. I used Racing Beat’s “header kit”, which is really just a big U-shape and two other lengths of their really heavy walled steel tubing pre-bent to a similar shape of their standard RX-7 header configuration and a mounting plate. You have to purchase the collector assembly separately. For some real backyard ingenuity, I took a piece of foam for insulating water pipes and used a coat hanger inside of the foam to make a rough mock-up of the header shape I needed. The crucial part is leaving enough room so the header doesn’t interfere with the end of the tie-rod with the wheels turned to the right. After I had my rough shape I cut up the “kit” pieces in smaller sections, tacked them together as I went, and finally pieced together the entire header. When I was satisfied it all fit I welded all the pieces together. It has worked great and once you grind the welds smooth and paint it, the whole thing looks pretty darn good.
You are completely right about the rest of the exhaust system. Mufflers just don’t seem to last very long. I too use a “glass pack” right behind the X in the floor. It was a lot worse when I had no interior, but now with a little extra padding under the carpet, and since I rarely drive with the top up anymore – it ain’t so bad.
You point on the oil cooler is important. I used the stock RX-7 oil cooler mounted in front of the radiator. It fits nicely under the cowl and the brackets were easy to build. I used the same mounting holes as the Alpine’s radiator, just using longer studs that stick out further to the front. This is the big oil cooler they used on the first generation RX-7’s. I would stay away from the water-cooled unit that mounts under the oil filter on the second generation Mazda’s, not having heard very good things about them. I think in Racing Beat’s catalogue it says Mazda uses the stock first generation oil coolers in their race cars.
I can’t say the throw-out lever was a big problem for me. It definitely is right up against the firewall in its furthest back position, but it seems like you wouldn’t really want to shove the engine and transmission any further back in the car anyway.
One point I did leave out is the rear end. My Mazda book says the RX-7 rear end is a 3.909, so the same as the Alpine, but I think the RX-7 has 14″ wheels. I’m not sure if that makes the difference; but I’m shifting out of first gear by the time I get across the intersection, the revs seem high to me at freeway speeds even though the rotary is a very high-reving engine, and my gas mileage seems poor. Someday when I get caught up on my other projects I’d like to try a Mustang II rear end. It seems like something around a 3.50 rear end would be more suited to the Mazda 5-speed and the Alpine’s little wheels. The rear disk brakes would be a nice update to the Alpine as well.
While not all that difficult, the electrical system was kind of tedious. Basically I left the light circuits, tore all the rest out and started from scratch. I wasn’t crying over losing the Lucas electrics, but it was a fair amount of work.
I’m curious what others have done about the cross-member and engine mount. Originally, I just made some cut-outs in the lower center section of the stock cross-member and welded some sheet over them. The rotary oil pan is wider than the Alpine’s stock engine. I actually used the stock engine mounts and made the front engine mounting plate out of 3/8″ steel plate. A little tech tip -make a mock-up with cardboard or fiberboard first.
However, in 1999 one of the pivots on the lower A-arm siezed up and I tore the A-arm away from the cross-member. For some reason I thought this was a good excuse to do a little cleaner and nicer job on the front mounting. I took a spare cross-member I had, cut the ends off and used square tubing to fabricate a new center section. I went to a local parts store and found some motor mounts that looked about right and made a new front mounting plate. Now it looks really nice and I’ve had no problems with it at all. I am a little concerned about ever selling it with a custom made suspension. I’m not sure what kind of liability I may have if it came apart, but I can’t really ever see selling this car with all these years into it. I guess I would just make sure any buyer was completely aware of what modifications have been made.
I really think this is a great conversion, but you don’t hear about too many people doing it. I’d love to hear what some of you have done if you’re out there.
Scott Rohr