Ok, I have two center housings, each with something potentially wrong with it. The first one I know leaked a lot of oil into the turbine and has a little bit of scoring and abrasion on the turbine side near where the turbine shaft ring would go, but overall it looks newer and less used than the second center housing. This is the clean one in the pictures, it was soaked in a lot of WD40 overnight, although it wasnt a whole lot dirtier in the first place.

the second one from a turbo I think overheated. I found a bit of burnt oil inside, it had a badly cracked exhaust housing and some discoloration throughout the center housing. However, it doesnt seem to have warped, and didnt seem to leak oil in the hour or so I ran it. This is the messy one, you can see the discoloration in some of the pictures.

I have a stock turbine housing and wheel, and a T04B compressor housing and wheel that will be going in one of these, as well as a new rebuild kit with all the seals etc. I just wanted your opinion on which center housing I should build up. Thanks!

Pics are shown in the thread in the 2nd gen forum here, i thought you guys might have more experience with this though.
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/advice-turbo-rebuild-663203/

 

The cleaner center housing with the damage in the turbine seal bore is no good. That bore is a very critical bore where tolerances are very tight and is where the turbine seal ring seats, and if you reuse that one, it is very possible that you will have turbine seal leak. You never know until you try though.

The second center housing looks like crap as well, but if you can get it all cleaned up, maybe I'd be able to evaluate it better.

Kevin

 

I know the first one leaked oil into the turbine, thats why its out of the car and disassembled. The second one didnt seem to leak, but the turbine housing casting was cracked inside and eating away the turbine blade, so it wasnt put on the car. At this point I could swap the good turbine housing and wheel, along with the T04 compressor wheel and housing, onto either center section, i just need to decide which. I'll get the dirty one cleaned up tonight, its currently soaking in WD40 to get a lot of the crap off, but there didnt seem to be any damage to that bore or elsewhere besides some discoloration. I got the brass bushings out of it without a problem, and the shaft spun freely (but with a small bit of play) before disassembly. What else should I look for on the dirty one?

Thanks for your response!

 

That clean center housing is unusable.

After you clean the dirty center housing, look for cracks from thermal stresses/overheating, and look at the journal bearing and turbine seal bores to make sure there is no galling to those critical areas. Also look at the thrust bearing surfaces on the compressor side of the center housing and make sure there is no damage there either.

 

Ok, i'll check those out... This sucks, cause both of these turbos were advertised as in very good working condition... and as is, they may not even be able to make one good turbo when combined

 

The turbine seal bore, journal bearing bore, and thrust bearing surface all looked fine, and I didnt find any signs of thermal cracking or damage after cleaning everything off, so I reassembled it and put it back on the car. The good news is that its smoking a lot less than it had been. The bad news is that it is still smoking. This is on a very fresh rebuild (no miles yet, just about 3 hours of run time, and pulling up and down my driveway), so i dont think its the motor itself. Any other suggestions on oil smoke?

 

Turbos will smoke for the first few minutes to burn off all of the oil in installation. If it is still smoking after a while, you can take your turbo off and disassemble the housings and it should become obvious where the leak is coming from.

 

it was about an hour of running with some loading and free rev-ing involved. I guess i'll pull it back off again... this is really becoming a pain in the ***.