Modified LS9/LSA blowers locking up

[Bruce Nunnally]

Jokerz Performance wrote:

Making an announcement for lsa/ls9 blowers. During the past couple of weeks I have noticed an increase in blower idling and locking up. Several calls and pm'd have come through with concerns. Work being done by different shops keeps the shops from being a direct blame. The constant facts have been cams upgraded pulley(increased rpms at idle) ported blower and outside temps ranging 85 plus degrees.

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[Cadillac Jim]

Pretty clear that the rotor was hitting the housing, indicating that supercharger damage caused the problem.  I haven't heard of supercharger problems, other than some versions of the spring-type isolator, anywhere else, even with mods.

[Bruce Nunnally]

I found this interesting alright.  May be an issue of long term exposure to additional heat via excess boost eventually causes an issue?

[Cadillac Jim]

It looks like a bearing failure near the end where the contact occurred.  That would be because of damage or overheating of the bearing.  If that's the end where the isolator and pulley is, it could have been damaged in mods, or a bad isolator could have caused a seal failure or some such.  People have been replacing the spring isolator with a solid isolator, and that could lead to damage.

The force on the bearings due to boost is the boost pressure times the area of the vanes, and doubling the boost and thus the bearing load should be within the safety margin of the bearings.  And, high boost is a short-term stress and is in itself unlikely to be the root cause of overheating in the bearings.

I would go with damage during mods or improper parts as a first cut.  An autopsy of several of the superchargers is in order to get a better idea.

[Bruce Nunnally]

When the pulleys are changed, they must be pressed off and pressed on.  There are warnings regarding which part of the snout is torqued and regarding clearances.  Perhaps it mostly works fine but occasionally the process leads to this.  Also not all replacement pulleys are oem balanced?

[BodybyFisher]

Are they putting a smaller pulley on them to increase boost?

If that is the case, as Jim said maybe with the increased heat and RPMs, the bearing is not up to the task?  The weakest link syndrome, new CAM, smaller pulley, then replace bearing.   I guess then the question is, is there a bearing that will hold up under these changes?

[Bruce Nunnally]

Maybe. I will be interested if we hear more details on this.  In the ongoing facebook thread they also point out that a factor is an aftermarket cam, and that perhaps low vacuum is an influence, since supercharger bypass depends on vacuum.  

[BodybyFisher]

I found that high temp ceramic bearings that withstand 500 degrees are made for a different application, but at least there has been thought given to heat

Navigate down the page to blowers and turbos, expensive bearings!

http://www.performancebearing.com/dragracing.html

Here is an interesting analysis of the Eaton supercharger

http://thehighspeedlab.com/supercharger-diagnosis.html

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Replacement High Temperature Steel Bearing for Powerdyne Superchargers BD-11A. 25mm ID x 52mm OD x 15 mm wide, Packed with Krytox High Temperature Grease to withstand 500 degrees without running out.