I bought an '81 Rx-7 on a Saturday. Got it insured and tagged on Monday. It blew up on the way home from work on Tuesday. Literally, it blew up. A friend of mine said he has never heard of a rotary coming apart like mine did.

Someone told me it was most likely the stationary gear that broke.

I can't seem to figure out how to upload pics from my phone. I do have pics in an album on my user page. I'll post pics to this thread when I get home tonight.

 

I have to say thats a pretty bad failure. I've never seen anything like it.

Heres the link to your album in case anyone wants to see it:

https://www.rx7club.com/members/retodd1000-151738-albums-catastrophic-failure-4114/

 

funny how he was able to post pix of it in another thread after it happened and still in the car. https://www.rx7club.com/new-member-rx-7-technical-256/12a-detonated-934425/

but anyway, i've never seen that before. but with those tension bolts backed out, it may have been a crappy build. maybe something thrown together to sell a running car. as for a broke stat gear, u wont know for sure til u tear it apart. probably nothing will be salvageable so looks like u'll be needing another engine. don't know if there's anything legal u can do since buying used cars is an "as is" sale but probably wouldn't hurt to check on it. and i think i'd get back in touch with the seller.

post u stated it was streetported https://www.rx7club.com/new-member-rx-7-technical-256/45mm-weber-streetport-12a-934090/. again i say it was built by someone that didn't know what they were doing.

i missed seeing this one in the introduction where u got it off ebay https://www.rx7club.com/introduce-yourself-254/new-member-owner-933939/

sorry to see u got such a bad deal on ur first rotary and i seriously hope something good comes out of all this.

 

damn, never seen or even heard of something this bad happening. I wonder what would cause something like that.

 

Notice that the two tension bolts that are "backed out" don't seem to transit the area of the housing that blew out any more... the piece of housing that came out still has a complete bolt channel attached to it. There should be a bolt runs through that channel, but you can't see either of them. They either sheared off in two places in the failure, or they never went all the way through to begin with.

Won't know til it's torn down, though. I wouldn't think high-tensile steel bolts would get sheared off by an exiting piece of aluminum like that under normal circumstances. Weird things can happen under forces as high as those developed in a running engine.

Judging from the amount of corrosion showing on the port side of the motor, including on the sealing faces, I get the feeling that you're going to find poor water sealing led to the corrosion of the tension bolts. May not have been the primary failure, but it sure didn't help any.

Stationary gear failure would let the rotor impact the inner housing like a 12lb sledge moving at x,000 RPM. But to literally blow a chunk out of the housing (as well as splitting it two places, left and right) probably required a power stroke to fire.

 

I wonder if your coolant froze and caused some cracks in the housing that then let go when you put some stress on it. Been unusually cold down that way lately. I'm looking at this picture in particular:

 

not sure about coolant , but if it was water in the passages it expands about 9% when freezing and can exert a force of nearly 100,000 p.s.i.

 

With the understranding you purchased this car this was no disrepect but that engine looked like crap, what is going on with the using the wrong exhaust manifold gasket? Thats for a SA engine I wonder if there were any other items cross between the SA and FB engines. While may not be a root cause it's still not right.

Well hope you either find a good engine quick or a good core to rebuild so you can drive and enjoy your car

 

I appreciate the input. I'm not to terribly heart broken about what happened. the biggest thing is the inconvenience is that it was my only car (thank God, I know a few people with extra cars). I really enjoyed driving it.

The bit of history about the car that I got from the previous owner was that it was owned by a friend of his. The engine was rebuilt 6 or 7 years ago. It sat for a while before the previous owner bought it. He owned it for about a year and a half before I bought it. Supposedly it only has about 7000 miles since the rebuild. I don't believe the guy I got the car from had any idea this would happen. I took a friend with me on the test drive. He has owned 4 Rx-7's in the past. This car ran great. It started without any problems. We let it warm up before driving it. It never got hot.

Now I will admit that I drove it like I stole it. Did that cause the failure? Maybe, maybe not. Who knows how much abuse it took before I got it.

One thing for sure, I'm being forced in to learning about my car. I had a friend of a friend give me a 12a to try to get running. After trying a couple of things, I still couldn't get the motor to free up. It had been sitting a long, long time.

I found a 12a on Craigslist in Davie, FL. '84 model with 75000 miles for $400, it had most everything on it. David, the seller, agreed to take it to Eric, a friend of mine, in Ft. Lauderdale. The engine was delivered last Wednesday, I borrowed a truck from a coworker on Thursday to drive south. On the way down, I talked to David. He told me that he had done a compression check before taking it to Eric, but the numbers weren't what they needed to be. He had another 12a that had been rebuilt and had about 10k miles. That was the one he took to Eric. So we loaded up the truck Thursday night, and I drove back to Tallahassee on Friday morning. Another buddy helped me start the removal of the blown engine on Saturday. I was able to get the engine out on Sunday. Not having the right tools is somewhat frustrating. At least now I have an answer for those "what do you want for your birthday or Christmas?" questions. Metric TOOLS!

Anyways, I had to wait on an intake manifold gasket, so I put that on tonight. My new engine didn't have an oil metering pump. While removing it from the old engine, the gasket got fudged up. I'm doubting I'll be able to get one locally tomorrow.

The new engine had a beehive oil cooler, where as my car has a FMOC. The seals on the old engine were all kinds of messed up, but the new engine seals look great.

Someone mentioned the exhaust header gasket was incorrect, the one on the new engine is different. Hopefully it is correct.

I removed the pressure plate and clutch disc from the old engine, thinking I'd take a look at the loose bolts. I don't have anything close to the size of the flywheel nut. If the tension bolts need to run the whole length of the engine, then my loose one have to be broken. They moved around too much to just be loose.

I've seen some threads of people doing rebuilds and swaps, so I figured I'd share something that seemed a bit different. I'll keep adding pics as I (slowly) get the bad engine disassembled.

Todd

 

Glad to hear you're going to put the car back to rights, rather than just scrapping it. I look forward to seeing what you find.

I'd be happy to loan you my flywheel wrench, but considering our locations, it'd probably cost more to send it back and forth than finding something local would.

It must have made an awe-inspiring noise when that housing let go.

 

just throw you block in the back of your car/truck and take it to a mechanics shop.. they will charge you nothing to crack that nut with an impact

 

Make sure to use the correct flywheel for the new engine. Not all 12A flywheels are the same. They need to be matched the rotating assembly. If the new engine has a beehive oil cooler, then it most likely is a 1983-1985 engine. There is a number on the engine side that can be crossed referenced at http://www.mazdatrix.com/faq/flywheel.htm. A 83-85 year flywheel will have a 31 on the engine side.

 

OMG thats horrible, but glad to see your putting another engine in it, hope its back up and going soon. Thats kinda how I got my 79 camaro, ran great when I test drove it, couple days later shes kaput. Found saw dust in the trans and a ton of coolant seal crap in the block, had to tear everything down and rebuild. Sucked *** but learned alot. Freaking scammers not that the guy u got yours from did, but I know for a fact guy I got mine from knew what was up by the expersion on his face when I had it towed to his house and droped in his yard.