I often browse the under $1000 vehicle ads on Craigslist, just to see what's out there and daydream about future projects. I was doing that last Thursday night without any intention of buying anything or starting another project, and I ran across an ad for a 1986 RX-7 shell for $500. That isn't any spectacular deal for an RX-7 without an engine, but it was really clean, and a rare Sport package, which basically gave it the turbo brakes/hubs, and suspension in the light stripped down base body and interior.


I bought one of these cars right out of highschool that was the same color, and also a Sport package. I had it for a few years then the engine went, as so many do, and I put it in storage for a few years before giving it to my brother because I was moving away. He never did anything with it, and ended up selling it about 10 years ago. It was the favorite car that I have ever owned, so many of the milestones in my life happened during the time period that I was driving it, and it's tired to so many memories and stories. The one car that I wish I hadn't got rid of, because I would probably NEVER be able to find another one like it...


So I'm looking at this ad, and thinking about how cool it would be to have another one just like the one that I had, and I start noticing things. It has a small ding in the hood in the same place mine did, there's a weird paint blemish on the B-pillar in the same spot that mine had one... I send the ad to my brother, and a friend that I was dating while I had the car, and they both think there can't be a coincidence. THIS IS MY CAR! I wanted to see if I had any old registrations or anything to confirm the VIN, so I look through my paperwork, and discover that I still have the title!



There ended up being a lot of drama when the seller found out that I had the title, but the short of it is that Rangmar and some other friends came to the rescue, it's now sitting in my driveway, and everyone is happy!




--Now for the plans --
I love driving rotary engines, but I swore a long time ago that I would never put another one in a car, they're just too much of a headache. Some people around here have been discussing putting a Kubota in something aerodynamic to make a high mpg for a while, and this seems like a good candidate. There is plenty of underhood room, people put LS1s and Toyota inline 6's in them.




My plan is to build it for both performance and MPG. I've already bought another engine, and with some research found that someone has dropped an Isuzu diesel on one before. There isn't much information out there about that, other than two forum posts and one picture.





*EDIT* Damned automerge - it's hard to break these things up into readable chunks when it won't let us post multiple times in a row!


There are a few issues. The stock gearing is 4:11, and the transmissions were about at the limit with the rotary's 138ft/lbs of torque. So to make this work, this is basically going to have to be an LS1 build, without the LS1.

Luckily, the engineering has all been figured out by others long ago. People commonly swap either a Ford Explorer 3rd member or one from a newer Cadillac with high gearing. There are a lot of transmission options, including the same transmission that is in my Jeep. Variants of that transmission were used in Toyota trucks, and the MKIII Supra, so different ratios are available, and I could just swap over the parts to mate it to a Jeep, and use the same adapter design that I already have.

 

Nice, can't wait to see it finished!

 

That is awesome! I have been daydreaming about a first gen RX7 for a while now. The 4.11 is a bit much but I think you can get a 27" tire in the back of that car and 70mph would be about 2400 RPM with a T5 (.68 OD) unless you're going to go with a T56... 6th on a .62 T56 would be about 75 mph at 2400 , the .5 OD version would be about 1900 rpm at 75. I mention the T5 because it's dirt cheap and seems a good match to the V2203's torque with a turbo. I haven't checked on a T56 or something else with a big overdrive (.62 or .5) and whether it will fit in the tunnel without mods.

I'm sure you have already looked at it but Granny's Speed Shop is full of information for the RX7 / V8 swaps. They have some interesting input on engine weight and it's impact on handling.. the V2203 is pretty light (for a diesel it's really light!), I bet it handles great! Really looking forward to your progress on this.

EDIT - when I'm saying .68 OD I'm referring to the V8 Ford T5's, they put all kinds of ratios in those things. You probably know that already, just wanting to prevent spreading bad/misleading information since there are so many different T5 gear sets. Sorry, I'm hung up on that transmission.

 

It will probably be getting a Ford 8.8 center section with appropriate gearing. The T5 is definitely on the list of candidates for the transmission. There is a ton of room in the tunnel, but the challenge is that the shifter on the Mazda gearbox is way off the rear. People swapping in T5s and other transmissions have had to do quite a bit of interior slicing and dicing.

I made up a quick mock up that's the same width and length as the block, and the same height as the bottom of he block to the top of the valve cover. The closest part is the steering rack. If I leave it where it is, I'll have to make the front 2" of the pan pretty flat, but it still has room to move back almost 3" before hitting the firewall, which would also help the shifter situation. Depending on what it looks like behind the dash, I'm also not against the idea of relieving the firewall enough to set it back a couple more inches. If I could do that it would have no problems with shifters or needing a different pan, and it would help centralize the 50lbs or so it will be gaining with the Kubota.

If for some reason I need to leave it where it is or move it forward at all, a Turbo II hood would be both lighter (aluminum), and have the hood scoop right where I would need to relieve the hood to raise the engine slightly.

The box off the front represents the front cover and oil pump depth.






Interior - Not too bad for sitting in a field for 6 years!

 

If you go t5, look for one from a Camaro or firebird. The shift is something like 6 inches farther back. Only thing is with the Camaro t5 is the tranny is tilted toward the drive a could degrees. Lots of info on t5 swaps on the HAMB.also you can get a s10 t5 and swap to the Camaro tailhousing/ shifter for better gearing. Also there in info there about using the cheaper ford t5 aftermarket shifters on Chevy t5

 

The autos had a 3.91:1 rear, which puts it at 1987.20RPM @ 60 with the .63 OD and 25" stock tire size. Not ideal, but gets it in the ballpark with a bolt in rear end. It should still get pretty good cruising economy at that RPM, and I've been considering building this engine to test some higher RPM theories anyway. A few people have spun them close to 4000RPM, which would be a bit over 120mph with that gearing if it had the power.

Someone has to try it first...

 

I like that attitude.
do you think you are going to run componds?


when you did the compounds what was the small turbo? I can't seem to find it in your thread when I was looking. I was thinking compounds in my truck and am making a new manifold. Found a t15 on eBay but not sure if it is too small. I am also looking economy but want to make as much usable power as possible.

I will be doing a run of SBC adapters here soon.

 

The small turbo was a TD03-08 from a twin turbo Volvo. The setup didn't do much better than that turbo alone. It built more boost, but not a lot more power, so I think it had some pretty extreme drive pressure. I think the big turbo was too big, and I'm not convinced that the TD03 is a very good turbo anyway.

I don't really see a benefit to running compounds unless you're really heavy and not able to get past the lower RPM lag quickly. The setup was very heavy and overcomplicated.

Heh, I'm not sure that I can afford one

 

If I can get enough interest I am going to do a discounted run. Will be reasonable.

on the compounds it was considering it just to do it. My truck is light. Probably 800 lbs lighter then a s10 or ranger. Probably as light as your rx7. It is hard sizing turbos for suck a small set of compounds. Not many example out there.

 

Hmm, flathead V8s had round bellhousings and inset flywheels. I wonder if these are at all close to the Kubota flywheel housing diameter?

Speedway Standard Chevy Trans to Flathead Adapter Kit - Speedway Motors, America's Oldest Speed Shop