I recently purchased a '79 RX7 with a 12A out of an '83. It wasn't driven much and I went through the normal cleaning routines... I sprayed about 1/2 - 3/4 of a can of carb cleaner into it while keeping it idling at 5000 - 5500 RPM. When I was doing this it smoked, but not any more than normal.

After I did that, it started idling properly and sounds much smoother (the carb. looks much better now). I also took the time to fix the points as they weren't properly adjusted. Now if I'm driving it and keep it under 5,000 RPM's it runs fine and sounds great. If I take it much over 5,000 RPMs it gets to a certain point and starts dumping a light colored (not white) smoke out the tailpipe.

it doesn't smell like coolant or oil, but I know it isn't good... Does anyone have a recommendation on what my next step should be? I've only put about 5 miles on it since I saw it smoke... I don't want to blow it up (or might it already be too late).

 

In the Archive, there is a thread by me titled "Coolant Seal Repair (maybe)". Look that up and see what you think. If it was oil, you'd know it by the smell. Same for fuel. Right? So all that leaves is coolant. That's my edumocated guess anyway.

 

dumping or puffing? For how long? Does it happen as soon as you take it to 5k rpm or if you rev it there and let off the gas? What does it smell like?

Usually, smoke at high rpm is the oil seals on the rotor worn out. It still has some life in it, but only tearing it apart and replacing those seals will cure it.

 

it will belch smoke until I drop the rpm's down... I held it at about 6,000 rpm for about 15 seconds and it stayed smoking the whole time. dropped it down to 4,000 and the smoke went away.

I fired it up since originally posting & it has a bit of an oil smell, so I'm guessing that it's probably an oil seal going bad. I'm going to do a full oil change & put 20/50 in it and see if that helps. This spring I'll likely buy a gasket & seal set and do a partial rebuild... there's only a few more weeks of driving weather left before winter (and road salt) starts.

 

there's no such thing as a partial rebuild. once u get it apart, u'll find there's more that needs replacing than originally planned. especially if it has well over 100k miles on it. u must us micrometers to take measurements of the seals to see if they're within spec to be reusable.

 

The engine (according to the previous owner) only has 40,000 miles on it. I'd get a full set of seals & gaskets and hope there isn't damage to the rotors or the housing.

A local gearhead (but one that hasn't worked on rotaries) has recommended me add 4-6oz. of ATF to the oil to try to make the seals expand. Would you recommend this or is that a bad idea?

 

Bad idea. Do not put ATF in your oil!!!

My last motor had blown oil control rings, and when you let off the gas it would leave a smoke screen that literally stopped traffic on the freeway. I started using 1 or 2 quarts of Lucas heavy duty oil stabilizer in the oil, along with Castro GTX 20/50, and that cured 95% of it. The only time it smoked after that was during autocrosses, when I was revving to like 8 grand then letting off, and even then it wasn't too bad. Worth a shot.

 

Ok. This isn't when I let off the gas... this is while it's still up over 5000 - 5500 RPM. once I let off, all the smoke disappears. I laid out a good 15 second (probably about 1/4 mile) cloud of smoke checking to see if it was a "poof" or a stream... when it didn't let up I let off the gas and the smoke stopped almost immediately.

I'll grab a quart of the stabilizer along with the 20/50 and see if that fixes it. I do all my work outside & it's supposed to rain until the weekend so it'll have to wait until then.

 

I wouldn't use 20/50 try some 5/30 or 5/20 instead. The thicker oil will hinder cooling and may cause more issues that it may seem to fix. I'd give the Lucas stuff a try with fresh 5/30 oil and see what happens.