I didn't bother cleaning the outside of the center housing. But I did use a fine
mill file to clean the openings for the oil and coolant banjo bolts. I stuck some paper towel bits in the holes to keep the filings out. If you look carefully at the hooked pick's tip, it's pointing to the old copper ring's seating position. If this wasn't cleaned, the high spots from the rust around it could cause leaks with new copper rings and possibly broken bolts from over tightening to try and "stop" the leak.
Just knock the rust off for a flat mating surface. Make sure to keep it even and don't over do it!
Here's the CHRA assembled. It SHOULD SPIN FREELY
! If there's any binding, DOUBLE CHECK YOUR WORK! If it's really tough to turn and you are POSITIVE the piston ring is seated correctly in the center housing's channel and no mistakes are on your end, DOUBLE CHECK that the shaft is NOT bent! It's possible to bend them with a hammer if you hit it wrong. Sometimes a little force is needed to seat the exhaust shaft's piston ring. If you used oil on the ring, it should snap in place with little effort.
When the turbo originally went, I pulled the center housing out and plugged all the lines off. I left the exhaust housing attached and made a simple block-off plate so the car would be drivable until all this was done. It was a blessing in a way as I discovered that the exhaust housing itself is EXTREMELY RESTRICTIVE. It's the T25's Achilles Heel. On some T25's from the 9000, you can port the opening oval like the gasket; using the gasket for a template, and port the header outlet to match as well. I covered this in another post, but on this housing, that's not possible as you'd grind a hole through the pipe or the flange. But you can widen the runner and go into the hole and remove some restrictions.
Look carefully at the T25 flange (turbo's inlet side with studs), see where it gets thin near the center of the flange? This is why you can't go oval ;ol;
Don't mess with the A/R (the area in front that encompasses the exhaust wheel). I hit the area in the back near the carpet. It's explained in the link below.
This minor porting helped the car TREMENDOUSLY with it's NA (naturally aspirated form) performance. 0-60 was 4-5 seconds faster, and I was able to climb a steep hill nearby with about 15 more MPH by the time I hit it's crest. The run before porting was 30 MPH and the car just held 30MPH to the crest. After porting it was at 45+. How the turbo even gets past this in stock form is a puzzle to me. I'm actually going to port a little more before everything is back in as I think I can get more performance out of it. Anyways, if you're going to "upgrade" your T25, I STRONGLY suggest porting this like in the pics especially if you start going over 15psi of boost. You should get better spool, better breathing, and lower EGT's. Well worth the 45 minutes of work. Stock T25's can surely benefit as well. Here's the original porting link with video links in it:
Hopefully this helps someone with their rebuild, upgrade, or just plain answers a question for them. Biggest trouble I had was the diagrams showing stuff being added that shouldn't of been. I also highly recommend "Gpop Shop". They were EXTREMELY friendly and didn't get pissy when I asked questions. They also have turbos for sale, but their site can be tricky to navigate at 1st and confusing if you don't know EXACTLY what you're looking for. The GT2860RS wheel and rebuild kit were from ebay, but the wheel is Garrett. I ordered the GT2860RS compressor housing from ATP Turbo. I replaced BOTH piston rings from the ebay kit with ones from Gpop Shop as I feel their quality will be better, and obviously the step gap ring isn't in the kit ;ol; The 360 thrust plate and all the other parts appear to be solid quality. I bought one of the $70 kits. Once everything is broken in, I'll post a video of some runs.