Anyone here know K26/K27 bolt/nut torque specs?

wild man · 05:03 AM

I am putting together a K27/8 for my 951S. But after hearing some stories regarding failures, I want to make sure everything is exactly right. I have some "ballpark" figures to go by, but so far I haven't found any figures specific to a K27 (or K26) to go by for the shaft nut and other bolts & nuts related to the turbocharger. Does anyone have these specs? I figured those on this forum would be more likely to know this info than those on the 951 forum. Thanks, Steve. Also, should I use blue or red loctite on the shaft nut, where only about 1/2 of the threads are engaged?

wild man · 11-21-2010, 04:20 AM

Never mind, it is already back together, going in today. My car has been down too long with all of the upgrades and other work going on. The reason the nut only engages 1/2 of the threads is because the 7006 compressor uses 2 sealing rings instead of 1, like the 7200 uses. That makes it a bit longer on the shaft. Since the nut came off and trashed the compressor wheel on my stock K26/8 just before it was scheduled to be torn down, I opted to use red locktite on the nut. But I also used some green on the thrust washers and the wheel, just for good measure. It does cause me some concern that there still seems to be a lot of radial play in the shaft with the brand new bearings installed. Is this normal for a K27?.

lucittm · lucittm's Garage

There should be no radial play if you prelubed the new bearings with engine oil. A small amount of axial play is necessary for the thrust washer to do its job, but is just enough to feel, not like a sloppy fit. Also, consider that the compressor wheel should be machined down to allow the nut full engagement on the shaft threads. You cannot get an accurate torque reading on the nut if the threads are not fully engaged. You are begging that nut to come off again. Consider the temperature in the unit and the high RPM, not to mention the torque on the shaft during rapid spin-up and slow down.

Good Luck,
Mark

wild man · 11-22-2010, 06:02 AM

Quote:

Originally Posted by lucittm

You are begging that nut to come off again. Consider the temperature in the unit and the high RPM, not to mention the torque on the shaft during rapid spin-up and slow down.

Good Luck,
Mark

I am not! I'm begging it NOT to come off. That's exactly why I went RED on the threadlocker used on the nut (and even used some green on everything else on the shaft). It's too late to machine down the wheel now - the turbocharger is being installed today. Thanks for wishing me good luck, I probably need it. But didn't you mean this the other way around? It should be almost tight axially (length-wise), and have some play radially (side-to-side), right? Because that's the way it seems to be, with the new bearings.

Could the looseness (it doesn't hit the housing) I feel now just be the result of not having any motor oil in it yet? There is only assembly lube on it now. But with the unit not installed yet, you can rock the shaft back an forth to where you can actually hear a metallic clack-clack sound. That does concern me, but I guess I just have to get over it and consider it normal. Thanks.