Hi everyone......this is my first post here (probably of many to come). I was hoping to get some answers on these funny "rotary" engines. I've done a little work on a few RX7's over the years, but this is the first time I'm gonna dig into the motor of one.

I'm helping a freind restore (resurrect) a 1979 RX7. The car has 38,000 miles on it (yes, that is actually correct). It's mostly been in storage in one form or another for the past 13 years. Aside from the long storage issues, the car is in surprisingly good condition....one tiny spot of rust and torn seats. And, it does run. Although, he had to have a local mechanic fiddle with it to get it running recently.

We're going tonight to take stock of the vehicle and see what it needs. I'm assuming all the rubber is shot....and everything is going to need a good cleaning. We've already got the obvious parts on order (suspension bushings, shocks, vacuum and radiator hoses...ect)....but, there is one known problem with the car.

There is blue smoke on start up. On a piston engine that's a dead giveway for worn valve guides or seals....but I'm not so sure about this rotary engine. Can anyone help us out with some suggestions?

Also....What are the common problems with rotary engines and RX7's in general?

Any help or suggestions are greatly appreciated.

Thanks in Advance.

 

The blue smoke is normal for a 27 year old original rotary engine, it's just excess oil burning off the rotors. At the top of the 1st Gen section is a FAQ thread that has anything about everything in it that you'll need. If you can't find what you're looking for in it, do a search and see what you come up with. If you still can't find an answer then feel free to ask. Hope everything goes well and maybe someday you'll be behind the wheel of an FB

 

Oil on start up is fairly common on a higher milage engine. Indicates the oil control rings are wearing. The smoke will usually go away once the engine has warmed to operating temps and will usually show only on cold starts.

Once you get the car to the point you can take it out for a quick run, run it through the first 2-3 gears to 6k rpm and watch for smoke. If you have none, you're good. If you have lots, with a fresh oil change of course, then it's rebuild time.

SAs are getting rare and that low of mileage is almost unheard of. Posting pics is not an option, it's a requirement.

Welcome to the forum.

 

Good to know this may not be the serious problem I originally suspected. The engine only has 38K on it though...so, I still think it's a bit odd to be burning oil. But, I'll know more when I've actually dug into the thing.

The car isn't actually mine, it's my freinds dad's. He's had the thing since it was new, and liked it too much to sell it. Now, he just wants a fun car to drive....and needed someone to fix it up for him.

 

If it continues to smoke after running, pick up a bottle of Lucas heavy duty oil stabilizer and follow the directions. Replace one or two quarts of oil with the Lucas, and make sure that you are not over filled with oil. The Lucas can help a lot with older engines...

 

The plot thickens......

I went down last night and went over the car and motor pretty thoroughly. For the most part, it was what I expected to see (for a car that has stood still for 15 years). All the rubber was shot and there is some minor surface rust in a few spots. But, actually....it's a pretty good candidate for fixing up.....really no body work to be done and everything that needs to be replaced can be unbolted. BUT, the motor problem is worse than I thought....so I'm hoping to get a few opinions on the motor.

Not only is there blue smoke upon startup but it doesn't go away when warm. It's burning about 2.5 quarts per 1500 miles, and it backfires pretty heavily when you let off the gas. I know this motor doesn't have a "valve train"......so it's not like I can just do a valve job to fix the problem. From what I saw in the FSM and diagrams, it appears to me that the rotor clearences are shot. and the motor will need a rebuild....does that sound about right?

I haven't torn apart the engine yet, but my guess is that the engine sat for so long (and in the humid east coast air of Connecticut) that the motor started to corrode on the inside. When it was finally started again, all that corrosion scored up the internals pretty badly....and now the clearence are gone. Does that sound about right?

Assuming I'm right. What are the options for engines in that car? Who makes a good remanufactured motor? About how much should we expect to spend on the block? Is there anything specific we should be looking for....or at....when we replace the block?

Also...the exhaust is gone...so we have to replace that. What's the best route for replacing that? I've seen a few aftermarket exhaust systems that look pretty....but, what is the optimum size pipe? who makes the best bolt on exhaust.....and is it just easier to take it to an exhaust shop and have them do a custom system?

Thanks again for the responses.

 

I dont know my stuff anywhere near some of the guys here, but shouldnt the smoking issue just go away with driving? If the car has sat for 15 years, theres going to be internal varnish and old oil and such that will burn off... maybe just driving it, hitting the redline a few times once its reaced operating temp will get rid of the smoking problem. As for the oil consuming, the engine is designed to burn about 1 quart every 1500 miles, using the OMP (oil metering pump) which injects the oil into the carb. it is located at the front left of the block. Anyway i hope this helps, but in theory, as long as your compression is good, the motor gets plenty of oil, and hasnt been overheated/warped from too rapid heating, it should be alright? i don't see how the rotors would be out of clearance in only 38K, unless mazda just put together a bad engine to begin with.. good luck man!

 

You won't know the condition of the internals until you open it up. You can get an idea by looking in the exhaust ports. Rotate the engine, feel the rebound of each of the 6 apex seals. Look for scoring on the inside bottom of the housing. With the rotor in the right position, you can boroscope from the exhaust port to just under the lower spark plug. That is where most of the housing wear occurs.

The smoke is most likely from shot oil control o-rings, tired old rubber. There is a possibility that the mop is stuck and over oiling, but that's a strech.

Unless the car was parked due to a bad engine, most of the hard seals should still be seviceable. You will need a gasket set, oil control o-rings, and springs. It takes more time to clean parts than it does to build these simple little engines.

What part of CO are you in? Are you subject to the Denver metro area emissions? If not, the best bolt on exhaust package is Racing Beat. Best header is SDJ, pricey. Best overall perfomance system would be the SDJ headers, a Borla XS/XR-1 pre-silencer and a good muffler, tied together with mandrel bent 2-1/4" pipe, 2-1/2" if you streetport.

The oem exhaust system for the SAs, 79-80 model, is quite different from the 81+ FB models, and no longer availible. The FB system can be adapted, but new is over $1000.

As a side note, even with the smoking, if the engine feels peppy and compression is good, rotors, hard seals and housings should still be good. With all the extra oil, it's hard for them to wear. If you are looking for a rebuild, PM me.

 

Since the engine sat so long, it may be a simple case of things sticking due to carbon buildup and dry seals. The Lucas will help with the dry seals, but to get the apex seals moving freely again we'll need to use a different approach. You can try this method which works very well for me: add a can of Seafoam to about 1/8 tank of gas and go for a hard (hit the redline several times) drive. If the seals were stuck, you should feel a change in the horsepower within 20-30 minutes of hard driving. If you continue to have these issues after all of this, then I would consider tearing down the engine to see what's going on.

 

Before the engine tear down, you might want to consider this. I've had real good luck with engine oil leak seal products like Bardohl's Stop Oil and Smoke. It softens up the seals and puts more life into them. I had a read bad seal leak and smoke at start up in my 84 GSL that was practically fixed using a bottle of this stuff at every oil change (3000 miles). I put about 50,000 miles on that car since then, the engine is still running fine. Still don't know what that engine looks like inside, curious but in no hurry.

Ray