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View Full Version : Bad Rotor pack Pictures of Damage to MPX



SCDan35thANV
05-07-2012, 02:43 PM
Well I was hearing some squeaking from my supercharger and was hoping it wasn't the rotor pack but with metal shaving in the supercharger oil I decided to tear it apart. Thankfully I got to it soon and I don't think the case is damaged bad enough to not use it. What is everyone's thoughts? Anyways on the market for a good used rotor pack until I get the money to go to my new setup.

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90coug
05-07-2012, 03:13 PM
Doesn't look too bad.


If you want another rotor pack I've got one. $50 shipped to your door.

Click here (http://i249.photobucket.com/albums/gg201/izepyck/Supercoupe%20parts/Supercharger/IMAG0071.jpg) for a picture.

SCDan35thANV
05-07-2012, 03:19 PM
Thanks for the reply. How are the clearances on the rotor pack is there any movement in the rotor pack? Is there any slop in the gears? Any idea on how many miles? I know we are supposed to have 12 thousandths clearance and mine was only at 9 thousandths.

Roadhawg
05-07-2012, 03:21 PM
The appears to be very superficial............

90coug
05-07-2012, 03:22 PM
Thanks for the reply. How are the clearances on the rotor pack is there any movement in the rotor pack? Is there any slop in the gears? Any idea on how many miles? I know we are supposed to have 12 thousandths clearance and mine was only at 9 thousandths.



I'll check the clearance when I get home. Miles are unknown

SCDan35thANV
05-07-2012, 03:27 PM
The appears to be very superficial............

Kinda confused as in what is superficial?

SCDan35thANV
05-07-2012, 03:28 PM
I'll check the clearance when I get home. Miles are unknown

Sounds good I'll PM you with my contact info thanks!

David Neibert
05-07-2012, 03:30 PM
Thanks for the reply. How are the clearances on the rotor pack is there any movement in the rotor pack? Is there any slop in the gears? Any idea on how many miles? I know we are supposed to have 12 thousandths clearance and mine was only at 9 thousandths.

I thought the rotor to case clearance was less than that. Back when I had an MPII and MPIII, pretty sure it was between .003-.005".

David

SCDan35thANV
05-07-2012, 03:35 PM
Thank for the response Dave. I talked to Charles and I could be wrong but I believe he told me 12 thousandths. I just don't want this to happen again. I plan on keeping the MPX until I can finish a few other things on the car such as my new transmission, solid axle swap, and then I am going with a different power adder all together. Can someone please clarify if I am wrong on clearances.

Roadhawg
05-07-2012, 03:44 PM
Kinda confused as in what is superficial?

Definition of SUPERFICIAL

a (1) : of, relating to, or located near a surface (2) : lying on, not penetrating below, or affecting only the surface

SCDan35thANV
05-07-2012, 03:51 PM
Definition of SUPERFICIAL

a (1) : of, relating to, or located near a surface (2) : lying on, not penetrating below, or affecting only the surface

LOL nice response I am assuming you mean the scratches are superficial. The scratch at the back of the case where the bearings are I can feel when I run my nail across it but it doesn't seem bad at all. The scratches on the side or in fact very fine and don't even catch with a fingernail so I would say those are in fact superficial. I was thinking you possibly meant that something I said about the rotor pack was superficial in which wouldn't makes sense anyways so I was a little confused.

davec73
05-07-2012, 04:55 PM
I just went through this and 4 to 6 thousanths cold is normal anything more than that you are going to have to overdrive the crap out of it without coated rotors. Ideal running clearance is 3 thousanths 9 thousanths is more than the mpx I had material removed from after a rotor pack explosion it was 6 to 8 thousanths and I was thinkiing of having it coated but it was less expensive for me to buy a new one.

SCDan35thANV
05-07-2012, 05:17 PM
Ya I just was following your thread and so the closer to the case the better? Also I am overdriving the MPX 25% so that isn't an issue. Can you please clarify exactly where to measure the clearance. I was measuring between the front of the case(towards the snout) to the end of the rotor pack and I was able to fit a 9 thousandths feeler gauge in there. Am I supposed to measure the clearance between the rotor pack and the outlet as well? I am new to this whole supercharge to rotor clearance thing and just want to be sure I am doing it right. Nothing in the factory service manual says anything about it.

davec73
05-07-2012, 05:25 PM
the center of the outlet on both sides between the rotor pack and the case so basically both sides of the triangle is what matters. there are tollerences that will push boost well the more thousanths you have between the case and the rotor pack the less boost it will push. most experts say between 2.5 to 3 thousanths when the blower is hot 4 to 6 cold

SCDan35thANV
05-07-2012, 05:41 PM
Ok thanks for clearing that up. Does the clearance between the end of the rotor pack (toward the bearing plate) not matter or does that need to be checked as well and what should the clearances be there?

davec73
05-07-2012, 06:00 PM
From what i understand the only tolerence you need to be concerned with is the one buy the outlet

SCDan35thANV
05-07-2012, 06:06 PM
hmmm ok. Well I know Charles from magnum powers was saying about adding more anaerobic sealer between the rotor plate and case to get the right clearances but I guess I will have to call him again to see if I miss understood. I will post up exactly what he says when I talk to him which probably won't be until tomorrow. I had written it down last time we talked but for the life of me I cannot find it.

S_Mazza
05-07-2012, 07:13 PM
You need SOME kind of clearance between the ends of the rotors and the bearing plate on one end, and the ends of the rotors and the rear case at the other end. The clearance at the front should not be shifting ... unless your front bearings are shot. The clearance at the rear could change based on how much sealant you used between the rotor pack and the case. That is what Charles must be referring to.

SCDan35thANV
05-07-2012, 08:13 PM
That's what I thought. Yes all the bearings are new, the coupler is new, and the snout bearings are new. The only thing that wasn't new was the used rotor pack so hopefully putting in a good used rotor pack should be the solution here.

Kevin Leitem
05-07-2012, 08:49 PM
I run 12 thou on the back inlet side, about 2 on the top oulet side and look for 5-7 on the bottom. You need to more on the back because the air being sucked in is trying to pull the rotors back against the rear bearings. I try to run as tight as I can on the top and leave as mush on the bottom as I can. Because the boost pressure is trying to push the rotors down against the bottom of the case.

If the rear tolerance is too tight you can use paper as a gasket and rtv on both sides of the paper. To adjust top and bottom clearance you can ream out the dowel holes a little to move the rotor pack up and down a little as you tighten up the bolts. You can use feeler gauges between the rotors and case to hold it in place while you tighten down the rotor pack.

In 10 plus years of running m90's spinning them extremely fast I have one hurt one. And that was my fault, when i was putting it together something didn't feel right, but I did not recheck. I think I knocked a needle bearing out when i slid the pack in.

Also I do not like the practice of icing down the blower between runs. Cooling the case quicker shrinks the case but the rotor are still hot and swelled.

90sc35thann
05-07-2012, 09:26 PM
I run 12 thou on the back inlet side, about 2 on the top oulet side and look for 5-7 on the bottom. You need to more on the back because the air being sucked in is trying to pull the rotors back against the rear bearings. I try to run as tight as I can on the top and leave as mush on the bottom as I can. Because the boost pressure is trying to push the rotors down against the bottom of the case.

If the rear tolerance is too tight you can use paper as a gasket and rtv on both sides of the paper. To adjust top and bottom clearance you can ream out the dowel holes a little to move the rotor pack up and down a little as you tighten up the bolts. You can use feeler gauges between the rotors and case to hold it in place while you tighten down the rotor pack.

In 10 plus years of running m90's spinning them extremely fast I have one hurt one. And that was my fault, when i was putting it together something didn't feel right, but I did not recheck. I think I knocked a needle bearing out when i slid the pack in.

Also I do not like the practice of icing down the blower between runs. Cooling the case quicker shrinks the case but the rotor are still hot and swelled.

I never gave a thought to shrinking the case down too quickly with ice but your conclusion makes logical sense. Nice write up. Thanks man! No more ice for me. I'll stick to my blue blower.

XR7 Dave
05-07-2012, 09:39 PM
I never gave a thought to shrinking the case down too quickly with ice but your conclusion makes logical sense. Nice write up. Thanks man! No more ice for me. I'll stick to my blue blower.

I concur. I lost a brand new MPX case AND brand new rotors due (as far as I can tell) to icing the blower between runs on the dyno. Put the ice on the IC, IC tubes or return plenum if you want to use ice.

Kevin Leitem
05-07-2012, 09:42 PM
I never gave a thought to shrinking the case down too quickly with ice but your conclusion makes logical sense. Nice write up. Thanks man! No more ice for me. I'll stick to my blue blower.

If you want to ice as soon as you get back from a run that is OK, but allow some time before your next run to allow the rotors and case to acclimate to each other.

SCDan35thANV
05-08-2012, 12:03 AM
I have never iced my blower for that exact reason you mentioned Kevin. I believe I read that somewhere before when you posted it. Anyways I took the inlet off the blower and found more scratches this time they were a little deeper than the other ones and I didn't notice them until I pulled the inlet off. In the pictures the rotors are in the case and my clearance to the top and bottom seemed ok. The top was 3 thousandths and the bottom was 5 thousandths but this is cold of course because the blower is off the car. With the rotor out of the case I can move them to the point they touch each other but the gears have no play at all in them. Also the rotors seem to turn fine and feel very smooth. I am picking up another rotor pack and going to put it all back together keeping these specs in mind and will post the results.

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