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I recently purchased my first Rx7 about a month ago. Story was the car was having transmission problems and the engine was probably low on compression. The transmission was already out of the car. Previous owner had no clue how to work on cars, so I took any information with a grain of salt.
My background; I have a performance shop and have been working on cars for 11 years mainly JZ platform. Engine, wiring, tuning, fabrication, etc will be done by me. Though I do have a friend of a friend that builds road race rotary powered cars. I pulled the engine yesterday, very easy with the tranny out, took about 2 hours working slowly.
The car will be built for road-racing, possibly street driven to the track.
The engine would crank over by hand in the car smoothly, so I knew it was not seized. After pulling the engine I cranked over by hand and coolant started gushing out of the exhaust, it wasn't doing this previously. I can grab the flywheel and spin the engine VERY easily. Guessing when I drained the fluids it allowed more coolant into the engine. I pulled the stock twins off to check out the inside and this is what I found. Looks like the rotor housing is in pretty good shape, I see no scoring and the apex seals are intact on all sides of both rotors. There is a bit of water in the housing but rust has not taken over yet.
So the questions are;
Does this look like a water jacket failure(definitely looks like water in the exhaust manifold?
Would draining the coolant siphon the coolant into the housing?
Is it likely the housing and rotors are still in good enough shape to rebuild?
If the motor is toast and not usuable as a core, I can save a bit of time and money not buying the engine stand for the tear down.
I would tear it down asap to avoid any potential water damage to the housings, irons, or rotors. All of the parts could be okay, but only a true disassembly will likely tell though. With a water seal failure like you have, you could have gotten lucky and had only the seal itself fail. In many cases however, a pertinent piece of the iron's water seal groove can be blown out leaving it ruined. Also the engine could technically have a breach somwhere else in the water jacket area. In my opinion a full teardown and inspection needs to be done. As for your LS swap dilema, I would say that it depends on your priorities.
Last edited by furious_rotation; 11-08-15 at 02:27 PM.
Reason: Punctuation
I would do a pressure test before you tear anything apart. This can not only be helpful det if its a water seal, but you can often hear which rotor its coming from.
I too was in this dilemma about a month ago and decided to give the rotary one more try. I would never go LS though, I was going to go with 2JZ. There is just something that seems wrong about stuffing a corvette motor in these cars. Buy a corvette if that's what you want.
I'll suck the water out and get a compression test done today. I'll spray some lubrication to try and avoid any further water damage. Probably won't have time to tear it down today.
As for the JZ swap, I'd love to do one, I have some engines sitting around. I've had about 30 JZ setups on personal cars from 1000hp down, but I'd like to keep the weight distribution closer to stock. Being a road racer lightest weight possible is my goal. The JZ is longer and heavier than the LSx and rotary.
Keeping the stock motor would be great to get the car up and running quickly. I'll tear it down and take some pictures. If it's not salvageable, I'll be going with the LS2/T56. The only pain is custom fabrication of the subframes and a Cobra diff.
I've always been a fan of the Rx7, I almost purchased one until I found a 63k mile MKIV TT Supra 10 years ago for a steal. Corvette don't have the timeless lines and collectability of the Rx7.
First off, I'm gonna say PLEASE don't LS swap it. Not my thing. I'll just leave that like it is.
Second, without question that's a water pumper of a motor, it's impossible for water to get in the engine normally.
Next, you'll need to figure out what you're going to do to get the motor happy. Cheapest route is to rebuild it yourself, it's not as hard as you'd think, but there are some pitfalls if you aren't careful. About $500-600 will get you an O-ring set and apex seals, you'll probably need more parts on top of that, but there you go.
You could also send the core in and get a Mazda reman, about $2500-3000. Or, send the core to an engine builder, about the same price. A reman is just a stock engine, a builder can port it, modify it, etc.
In the middle is a used JDM engine, you can get a long block with trans for around $2000, but it's a crap shoot if you get a good engine. You do typically get tons of parts for building a good motor, and it's an easy way to get parts you may be missing or are damaged (wiring harness, intake manifolds, injectors, rat's nest, etc.). You also end up with a good pile of low-mileage parts that can be sold to recoup cost.
We're here to help and answer questions, get that thing happy and it will put a big smile on your face.
I'm a huge supporter of keeping the rotary but have respect for whatever application you use. It isn't that hard or costly to build a 4-500 hp single setup that is reliable. For me, it is the experience that the engine gives you as a driver. Once built right, they can be very cheap to rebuild as well, if nessisary.
If the core doesn't have catastrophic damage and is rebuildable for $600-1000 I will go that route. I'm seeing the rebuild kits for $1200-1500 range which is a bit steep IMO for O-rings, a few gaskets and apex seals. That route would leave me with about $5,000 of LSx/T56 parts from my previous racecar which was an SC300 with an LS1/T56. I could use that for cosmetic and suspension modifications. I'd hate to spend $2k on a used JDM engine and need to rebuild it as well. I will have some time to tear it down this week.
I'm not the biggest fan of swapping the Lsx in the car, for "form". But on the other hand "function", road-racing, which is what the car will be doing 99% of the time highly benefits from the low end torque and low heat generation of a big naturally aspirated engine.
I went from 350RWHP JZ motor to a stock 300rwhp LS1. The Ls1 wasn't special or fun in a straight line, but it made the car 7 seconds a lap faster on a 2.3 mile track, and lowered my operating temps 20-30 degrees. Still nothing beats the feel and pull of a nice turbo setup.
Basically it comes down to money, time and functionality. I don't want to drag this project out for months/years.
For the 13B, I need to rebuild the engine and buy a 5spd transmission($2500). Single turbo, injectors,V-mount intercooler, exhaust manifold and stand-alone($2000) (I can sell the LS2 shortblock for $1500-2000). 400-500RWHP
For the LS2 I need to buy heads, driveshaft, Cobra differential and fabricate subframes. $3000 and a lot more work w/ fabrication/wiring for 450-475RWHP
I've had both a rotary and an LS3 swap. If you are not familiar with the rotary set up it could be an expensive learning curve. Particularly if you have apex seal failures, they can fail for many reasons and if you don't get to the route cause putting a new motor in with result in just another blown motor in almost no time at all.
The rotary is refined for the car because it comes factory. An LS3 swap has a ton of power N/A and for road racing it's easier to drive because the power is more linear and predictable. The T-56 is a clunky trans and mine shifted like a truck. If I ever did another swap I would do a TR6060 or T-56 Magnum. The regular T-56 out of a 98-2002 Camaro doesn't compare. It's very truck like and I dislike it. Maybe if you built one with nicer aftermarket upgrades it would be ok.
The stock RX-7 rear isn't ideal for a swap for strength and gear choices. All the subframe's you need are available through Samberg. They make some nice products for an LSX swap. Sikky makes a kit and of course the least preferred Hinson kit.
Ronin makes a nice Ford 8.8 subframe for the swap that's ideal.
Norotors.com has a lot of swap info and there are some JZ swap build threads on there as well.
Rotary motor is cool but it has its drawbacks. JZ is a tight fit in these cars. LSX motors fit better.
First off, the "rebuild kits' give you a TON of stuff that you might not need. I find it way better to go through the motor, see what's needed, then order what's needed.
Atkinsrotary.com is a great source for rebuild parts, they have great prices and good product.
If you are missing parts, or if you need a transmission, I would consider getting a JDM long block. You'll have a good transmission, another motor for parts, and tons of parts to sell. Or, get a JDM trans for $400 or so if you just need that.
Many things in the motor can be re-used if they're in spec and not worn out. Side seal springs if they aren't torn up on removal, corner seal springs, corner seals if the sides where the side seal touches isn't worn, apex seal springs, oil control metal rings and springs.
Get some good non-Mazda apex seals, I'm not sure what the hottest ones are now, but the newer apex seals can take a LOT of abuse without blowing. I've seen detonation so bad it dented the face of the rotor, the apex seal was fine and re-usable.
Also, get the coolant out of that motor and get some sort of oil or WD-40 in there to keep it from rusting up. I've seen rotors that were so rusty you couldn't get any of the seals out and had to be junked.
Awesome! Thanks everyone for the great info. Luckily the car came nearly complete, so I have pretty much everything other than the transmission, gauge cluster and ECU. I sucked all the water out/cleaned it then filled it up with gear oil and other lubes and pumped any residual water/crap I could out of it. Good to know about the aftermarket seals, if I'm building the engine I want to build it for high horsepower/E85. I will have failsafes for oil pressure, oil temp, knock, AFR, water temp, etc. A string of gauges and a sensors, 50 row oil cooler(more if necessary), accusump, dual pass radiator, v-mount and proper ducting. I was pulling well over 2g's with my last setup on used slicks.
I definitely agree agree with the LSx NA linearity, it makes it so easy to drive it almost feels like cheating, lol. My T56 has a power tower short shifter, and it definitely takes some getting used to, gears click into place almost like a gated shifter. With my last track JZ setup, it was a lot of modulation to keep the boost/tires in sync. The head HPDE instructors hopped in at TWS a few years ago, and all I could see from my peripheral vision was his head bobbing back and forth to the beat of the blow off valve as I modulated the throttle. He was scared, didn't say a word until after I dropped him off. Turbo'd cars have a feeling of being much faster with the sounds and driving technique required, harder to drive, but much more rewarding when driven to the edge, or off the edge of the track.
I'll be taking everything apart sometime this week or weekend when I get time and will be able to asses what all needs replacing. I'm almost certain this engine has been rebuilt before so maybe I'll get lucky.
Last edited by Logan-mascheck; 11-09-15 at 09:34 PM.
Well, three months later and I finally disassembled the engine. The front pulley bolt was stuck on like crazy, took 10 foot breaker bar. O-rings were completely fried. Housings look OK. Rotors are a little rusted but may be OK. Two of the irons are toast, the water O-ring slot broke/rusted off near a water passage, which is probably the main reason it was leaking water so badly. There is weird white crap all in the motor, almost looks like vasoline or something.
I traded my LS1 for what I was told was a rebuilt 13b-REW, turns out it was not rebuilt and it's just a JDM pullout 13b-RE. I got the transmission/driveshaft/flywheel/clutch with it, not sure if it's and Rx-7 tranny or what. Dumb on my part, for not doing a bit more research, but the LS1 had been sitting in my garage for a couple months and no bites at $1500.
I could probably use it with modifying the mounts on the 13b-RE, but at this point I may just sell it... So now I need two Irons and possibly rotors. With the cost of all those parts I could have a beefy 475RWHP LS2/ T56, which is sitting in my garage and just needs heads. The Rx-7 transmission will be a crap shoot at 400RWHP. My plan for the turbo setup on the 13b was Borg warner EFR or SX-E and cast manifold, with v-mount setup. I'll get pictures this afternoon of all the parts, maybe you guys will give me some other options to get the car back on the road.
I've read people welded the irons, I have a tig welder, but at 300-500RWHP, I think that's probably a bad idea. Especially since the car will be road-raced for 30 minute sessions.
Well, a little bit of good news after searching. It seems that with a bit of modification and swapping parts over I can put the 13b-re into the FD chassis by notching the frame and fabricating motor mounts. These look super simple compared to other swap components I've fabricated in the past.
The 13b-re is now on the stand for partial disassembly. I'll compression test the engine, if everything seems good, I may go forward with installation. I may do a rebuild depending on how the results look and what I find when I pull some components off the engine.
Here's some pictures I pulled from another thread, regarding the modifications to fit the 13b-re
11-08-15, 10:08 AM
. Turbo'd cars have a feeling of being much faster with the sounds and driving technique required, harder to drive, but much more rewarding when driven to the edge, or off the edge of the track
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