cant believe that much slop is "just how it is". geez

 

Just to update this, I rebuilt the turbo the other day. It was pretty simple. I marked the shaft, compressor wheel, and nut so they lined back up for balancing. I was more concerned about the oil leaking rather than the shaft being loose after some posts to this thread. There was a lot of carbon inside, and it looks like the oil got pretty warm inside there. The turbine and shaft looked very good, and I cleaned it up with fine sandpaper. I think the shaft play comes into play because of the length of the shaft, where the bushings/bearings are located, and the bushing/bearing design. The overall length of the shaft is about 9 1/4", and the bushings/bearings are about 1 3/4" apart. So if there was a .004 clearance between the shaft and bushing/bearing and the shaft is 2.14 times longer from the edge of the bushing/bearing than the width of the bushings/bearings than that .004 clearance would show up as multiplied by 2.14. And not only that, but the bushing/bearing spins inside the housing, so there would be about another .004 clearance on the outside of the bushing/bearing. So if I did my math right that would translate to .034" play at the tip of the shaft with .004" oil clearance. It does tighten up a little when it is hot. I would really like to make bushings/bearings that have an oil groove on the outside so that it would not spin in the housing. I think that would take away half of the play that you can see. I have a couple brand new Precision 61mm turbos for another project, and I checked them. They also have a little more play than I thought they would. I havent had time to mess with the return line, but it is in the front corner of the pan. It comes straight off the turbo, and bends towards the pan. Maybe that is my problem. I will be looking into this further.

 

The bushing must spin. Other wise it won't handle the shaft speed.
Burn up and cause all kinds of problems.
If its crusty inside your could have burned the oil with a hard shut down or start up.
Think the compressor wheel/shaft will never see the side load you are doing by pushing on it.

 

Oil temp too high? Smaller feeds will do that too. I think I remember you have a big enough feed line. I went to a straight 6 an with a 1/4" fitting off the galley. 1/8" to 4 an is necked down at the fitting. Can't remember exactly but I think the 1/8 fitting I was using had a 0.190 id which was pretty small.

 

This is true. In NY the racing season is real short, so there are only a couple days left. I really want to run it down the track as I have never made a decent pass. I will mess with it over the winter. I plan on tearing the engine down this winter to check things out. Plus I think the rear main or cam sensor is leaking.

 

^^^^ This... The shaft spins in the bushing and the bushing spins in the housing. Like Rick said, that is the only way that small bushing can handle the 100,000+ rpm shaft speed that it sees. Also why there is so much oil clearance in the bushing.