Theoretics 1973 Rotary Wagon

So one or two of you homos asked for this so I'll subject you all to it. I'm mostly maintaining it on GRM where I'm pretty active but I'll mirror it here so feel free to hit me up if you have questions. Enjoy.

Introduction:

I’ve sadly put a bit more thought into how I’d like to introduce and structure this project than a lot of other things I’ve done in my life. Any of you familiar with my meandering writing style on the forum know I have a tendency to repetitively edit posts after hitting the submit button. This isn’t out of fear of being wrong on the internet, but rather an attempt to clean up fragmented thoughts and clarify things after I smash the submit button. Every now and again the thought that I should really put some effort into attempting to become competent writer floats top of my list of priorities. So here’s my initial attempt at it.

The subject of this project is a 1973 RX-3 Rotary Wagon. The RX-3 “Savanna Sports Wagon” was only brought into the US for one year from 1972 to 1973. This is an S124A chassis which means it’s a real deal Savanna Sports Wagon, not an 808 converted to look like one. Since it’s a Series I RX-3 variant, it once played host to a 12A good for about 110 HP in North America. That engine is long gone which left me with a blank slate. More on that in a bit.

I posted a bit about the car when I was looking to buy it, then again shortly after I bought it, but the project has run into roadblocks as my life has been in flux for some time.

The primary issue is that my previous career was a field technician for a DoD contractor. While it was a great job, I spent between 8 and 10 months a year out on the road. The handful of months I was home never really lined up with my friends schedule, from whom I agreed to buy the car, and a severe restriction on project time as I was renovating a house and spending time with my family.

The second reason is that I left aerospace to work in the ERP space just before my son (backup child) was born. So, in addition to moving across the country and a paycut, my spouse and I now have an additional child, another house which needs some work, and the seemingly endless process of settling our first child into the new home.

All that for a forewarning that this build is going to be slow. The car isn’t going to be returned to stock but instead an OEM+ type configuration. I can poach, refurbish, or fabricate-to-fit the vast majority of the parts that are missing but certain items, like all the door seal rubber, appear to only be available from sources located overseas. That drastically increases the price of components so I’ll have to see exactly how inventive I need to get.

So with that out of the way, here’s the story of how this came to be.

 

Background and Purchase:

Several years ago I was working 3rd shift and, while on the flightline performing some servicing and preflight checks, I was shooting the E36 M3 with a coworker from our other flight test facility who I knew also had an interest in cars. Eventually the subject of who owned the heavily modified Mazdaspeed3 in the parking lot came up and I admitted it was mine.

It turns out that he is a serious rotary fanatic. He owned a number of 60’s and 70’s rotary cars including an RX-2 and an R100. So we started talking rotary cars. He had some stories about what his family had built and we hit it off. I had played with a friends FB in high school, nothing real serious, and was kicking around the idea of buying an FD. I joked that what I really wanted though, was an RX-3 wagon. Someone here on GRM had posted a craigslist ad to a pretty rust eaten one a few months earlier and, for some reason, I was smitten with the idea of owning something which represents that level of automotive absurdity.

He comes back with “I have one in my barn. My brother and I painted it a few years ago but never really did anything with it. It’s missing the engine but are you interested in looking at it and potentially buying it?”

“What? No way.”

He then proceeds to show me a picture of it.

Yea, I’m interested.

Several years go by and we finally meet up to look at it. It’s as described, doesn’t have any rot or crazy bondo slabs, and the interior is pretty much intact. So I agree to buy it but I since I was leaving for a trip either the next day or a few days from then I didn’t have time to arrange transportation.







Fast forward another year or so and I’ve sold the California house and moved to Pennsylvania. My friend gets back from a trip and we line up a truck to bring the car across the country. I insisted it be hauled enclosed as front glass is unobtanium but I was able to find a transporter who didn’t just laugh at me. I wish I had the pictures of this but the transporter had the RX-3 in the front of an enclosed trailer with Lamborghinis and a heavily modified Ford GT he was dropping off in Chicago. On delivery, pulled out some sort of chopped and bagged 50’s Chevy on the way from West Coast Customs to a new buyer here in PA. I’m fairly certain the Mazda wagon was the most worthless thing he ever transported but he was nice enough to laugh and tell me no when I asked.

Anyway, I got it home and it’s sat there for the last year waiting to get started. We’re now something like five years into this and all I’ve accomplished is the receipt of the car and changing the title to my name.


[doublepost=1533841496][/doublepost]The history of a plan:

When I initially started thinking about how I wanted to put this project together I was pretty well set on a S6 13B-REW. The swap into RX-3’s is pretty straight forward it just typically requires a turbo II transmission to overcome the weird rear transmission mounts used by the FD RX-7. Seems easy enough, at least as far as engine swaps go.

Unfortunately, my plans for grabbing a cheap Japanese S6 motor online were rudely ruined by a gaggle of eBay sellers who are having some sort of pricing competition listing motors 2x to 3x times over what they were just two years ago. That took the secondary market with it and prices have become stupidly high for used motors of unknown condition. At $1800 I could make a case for the risk as I was going to tear the motor down anyway. At $3600 or $4000 that risk becomes a project killer.

That caused to me to reconsider the path I was on. I was thinking I was going to build a 400 HP turbocharged monster when I bought the car. After looking at it for a bit, considering how I’d actually transfer that power to the ground, and the interior, this was the wrong platform for that application. My personal style is an OEM+ type of look and feel. Improve the handling and mechanicals of the car while only putting forth some subtle cues that things aren’t what they seem. To get the level of grip I think I’d need, the rear tubs would have to be extensively modified to fit wheels larger than the GSL-SE wheels currently on it. That means I’d have to pull the rear seats, which isn’t an option. I also likely can’t flare outward easily due to how the arch overlaps the rear door.

At that point it seemed like the right thing to do would be to fit a less expensive NA motor into the car which would simplify the plumbing and still offer reasonable gains over the 12A it was initially fitted with. As if the internet read my mind, SpeedHunters posted this at about the same time running on a heavily modified NA 13b. Unfortunately it seems like cheap NA S4’s and S5’s have basically vanished off the face of the planet, or I’m looking in the wrong spots, so onto Plan C.



So onto the backup plan. NA RX-8 motors are still cheap. They suffer from a stigma related to an oiling issue in the first generation but it seems like if you actually take care of them they don’t have too many issues. It was also still possible to pick them up for $1200 to $1800. The bonus was that PAC Performance has been documenting the progress of their 13b-MSP build. In its final naturally aspirated form PAC coaxed 200 whp out of the MSP without any kind of crazy modifications, rebalancing, or lightening. The shop then moved onto building, and giving some consideration to, putting together a 400 whp turbo kit, but a 200 whp NA motor provided enough headroom that I could mess with it if I wanted.

Link if you want to learn about Project 500.

While I’m fishing around for the quirks of the 13B-MSP and considering pulling the trigger, a member chimed in that he’ll sell me a S4 motor, harness, and ECU out of his challenge RX-7 to zero the car out. Apparently he knew where to look for a cheap one... That pretty much cinched the engine choice as it significantly lowers the risk and barrier of entry allowing me to build something fun to drive without breaking the bank. It also allows me to use the stock RX-3 rear end instead of going the cut down Ford 8.8 or Volvo 240 routes I was originally looking into.
[doublepost=1533841531][/doublepost]Work Starts

Again, just a warning, the pace on this is going to be glacial. Hopefully this thread gets me off my ass and into the garage at night.

The first thing I do when I buy a car is grab the factory service manuals. I’m not super picky about digital or paper but locating a digital copy of a 1973 RX-3 and it’s electrical diagrams… yea. Off to eBay. 35 dollars later I have an engine manual, REAPS manual, and wiring diagram.

(picture of manuals)

Andy was cool enough to brave dropping off the RX-7 at my house so I could try to test the engine before I pull it.



Things are a bit… shall we say tight, at the top of my driveway. Eventually we were able to get it into the garage by pushing it in most of the way with the Vibe then straight human power. Considering how many non-running cars I bring (or limp) home I should probably just bolt a winch and snatch block to the floor.

Anyway it’s in and I am starting to investigate the motor before pulling it after a pretty significant delay. Which is where I’ll start with updates.
[doublepost=1533841618][/doublepost]I had my home AC serviced a couple weeks ago. I asked the company that did that to de-service the AC on the RX-7 while they were on site as the RX-7 appears to have an R22 system. They seemed a bit surprised by the request but did it anyway. Doing my part I suppose.

Investigating the RX-7 a couple of things stood out. First off the interior of the car is fantastically well kept and the top of the engine is pretty clean. That was a major factor in purchasing it.

Second when you look a bit closer the front cover has RTV on it. Which means it’s been off at some point. Not uncommon but if it’s just that, there was probably an oil leak at some point.



Third the neck where the water which goes into the housings has RTV and other goo on it. So probably also water leak then. I was half planning on tearing it down anyway so probably not a huge deal since most of that can be hot tanked off.



Pulled the shroud and radiator fan off so I could get at the front of the motor to ensure it turned.

The engine turned ok and seems to have compression so that’s a good thing. So I set to work pulling the radiator and cutting zip ties to liberate the various components I’ll need.

The radiator hoses are held on with worm drive clamps, rather than spring clamps, (or both in this case) and the radiator hoses all appear to be new-ish. So obviously someone did some work to this trying to isolate a leak or other problem.



Coolant was green in the expansion tank, nothing appears to be out of the ordinary there besides being a bit full.



Unfortunately when I pulled the petcock out of the radiator the water was brown and smelled like…. Water. Crap. Looks like it was a cooling problem which adds up based on the work done on that side of the house. Hopefully nothing is cooked but a teardown appears inevitable.

Finished pulling the hoses off the the radiator and neck to find some sort of white waxy goo in the motor with no sign of coolant. If I wasn’t going to rebuild the engine it’s sure as hell getting done now as I'm willing to bet this is some sort of stop leak.



The oil metering pump is also a gigantic mess but it’s the mechanical which was important to me. I'm hoping I can rebuild it because Rotary Aviation makes an add-on which allows users to run two stroke oil in place of the engine oil through the pump. That should clean things up a bit and avoid having to premix when I fuel up.



Goal for tonight is to finish freeing the engine loom and computer as well as uninstalling a few other components.

 

Sick wagon! I've always liked those things.
If you go to the RX-7 club and hit up members Fritz Flynn or Max_Spd they're usually parting out an RX-7 or two. Might be a good resource for clean parts for the engine. I'm 99% sure you can find a nice OMP.
gl with the project

 

Thanks for the tip I'll look them up after I take stock of the damage.

I didn't accomplish anything the night before last as I fell asleep with my daughter. I keep hearing I should try to get as much affection as I can while she's young as eventually she'll grow up a bit and I won't be unquestionably awesome anymore…

Last night I found out why you remove the engine loom as part of the engine assembly rather than independent of the motor. The routing makes it such that you'd have to pull the vast majority of the power steering, fuel, brake, and AC hoses to get to the sensors on the backside. Newer cars are quite a bit better thought out in my opinion. I'll rethink the routing when I install it into the RX3.

Tonight's plan is to the RX7 on jackstands and get the exhaust and prop shaft disconnected. Then I'll need to borrow an engine hoist and figure out hoist points. I'm doing this an hour or two at a time but progress is progress.

 

Love it!

 

Quick MSO update since another question was asked about the engine decision making process and there was a post on GRM about the goo.

The goo in the upper radiator neck is indeed the result of not changing your coolant on a semi regular basis. Apparently it's magnesium and various other hard minerals that fall out of the coolant as it ages. Used distilled water kids.

I'll expand a bit on the motor choice a bit more here as I'm not sure how many of you are plugged into the GRM $20XX challenge. If you're not up to speed on it the goal of the contest is to build the an "all arounder" race car that's fast in drags, autocrosses, and shows well in a concourse for the same number of dollars as the year. It's a fun time and really brings out some crazy low buck engineering. Part of what you can do to reduce the costs is zero out the amount that you paid for the car. In this case GRM forum member Andy bought the RX-7 for $600 bucks and, since that's all he can recoup for the challenge, I bought the long block engine, trans, and ECU for $600 bucks to zero his car out. It's going to play host to a V8 eventually.


The risk analysis for the motor purchase was as follows:

I can still likely use the side housings even if the rotor housings and rotors are trashed. If I open up the motor and everything turns out to be ok, then it was just a bit time consuming to get everything out, cleaned and rebuilt.

If I were to buy a JDM engine for 5x the cost I'd still be running the same set of risks as this NA motor, as no one will warranty one of them, and have even less money to rebuild should I found the housings and rotors trashed. I'll still need to tear down the motor to ensure it is healthy all I'm saving is the time getting the engine out of the car.

The third alternative was to buy a rebuilt known good motor for $4500 to $6000. At that point I'd need to wire it (possible as I was an avionics tech at one point), adapt a transmission (TII transmissions are about $800), get accessories (all I can see is $$$) plus all the misc stuff like the ECU that also goes with it. That's an even more expensive option but the least time consuming. I have time right now as I'm not in a massive rush so this was off the table to start with.

The long and short of it is that even if I come out of the tear down and find it's a catastrophic loss, I'll still come out ahead of the other two options. Coupled with a semi decent understanding of how much power I can realistically transfer through this thing it was the least risky choice, especially since I'm not faced with a timeline.

 

I don't wanna mess up your math too much, but I just had the engine in my FD RX-7 rebuilt and I'm over $20k in. I went big and had it done by an expensive shop (Addicted in Tennessee) who used a lot of new parts, but yeah. Prepare your anus. Rotary mechanics are hard to find and they'll charge you an arm and a baby's leg.

 

Yea it can get expensive quick. Worst case I now have all the accessories and need a short block. Best case I have the housings resprayed and lapped for 600ish bucks, get a master rebuild kit with apex seals and new tension bolts. With other miscellaneous items it's still half the price of a short block. Still a couple grand though.

Having the skills and time to rebuild it myself helps a lot with keeping the costs down.