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Thread: Clearances between rotors & case on M90

  1. #1
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    Clearances between rotors & case on M90

    Can anyone out there tell me the clearance specs between rotors and case of the Eaton M90. Is it diffrent for teflon coated rotors and earlier bare alum rotors. How much wear is considered acceptable on the case or rotor? I have not seen much information on tolerances so I would like to find out.

  2. #2
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    I know a lot of you guys play around with the superchargers on your cars, porting and what not, trying to get more performace out of them. Does anyone check to see if all the work they are doing on their supercharger isn't being done on a wore out supercharger? I have had one reliable source say he believes its .005 for the older models and .003 for newer style. Does that sound about right to you guys?

  3. #3
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    Ken,

    I believe Charles Warner said they try to maintian .004" on the bare rotors. We measured my old MPII and with a set of late model teflon coated rotors it had .002" clearance on the areas we were able to measure with a feeler gauge. My current MPII has bare rotors and about .004 clearance. So anywhere between .002 and .005 will work fine.

    David
    91 SC AOD 4.2..2.3 Whipple........10.92 @ 126.70
    93 SC AOD 347 Turbo.................10.04 @ 138.99
    My Garage

  4. #4
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    Quote Originally Posted by David Neibert
    Ken,

    I believe Charles Warner said they try to maintian .004" on the bare rotors. We measured my old MPII and with a set of late model teflon coated rotors it had .002" clearance on the areas we were able to measure with a feeler gauge. My current MPII has bare rotors and about .004 clearance. So anywhere between .002 and .005 will work fine.


    David
    Thanks David that confirms what I have found out so far. You run a lot of boost from you supercharger, is that because of the tighter clearances? I have a set of teflon coated rotors to install in my Eaton. I am just waiting for a rebuild kit from Wynn. Thanks for the info

  5. #5
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    Ken,

    With the heads and cam I'm using, I get the most power overdriving it about 23%. I get 10% with a bigger jackshaft and another 13% with a smaller pulley. I'm not sure just how must boost it makes because it pegs the gauge as quick as I floor it, but the fuel pressure gauge shows about 17 pounds over static pressure, so I guess that what it's making.

    Your better off with teflon coated rotors (gained 1-1/2 pounds of boost on my car) and slowing the blower down. Even the best ported M90 out there has lousy performance at the rpms I'm spinning it. It pulls a bunch of power off the crank and really heats up the air. Mine shreds a jackshaft belt every few months.

    David
    91 SC AOD 4.2..2.3 Whipple........10.92 @ 126.70
    93 SC AOD 347 Turbo.................10.04 @ 138.99
    My Garage

  6. #6
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    Oct 2004
    Location
    Indy, IN
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    Coating?

    I know this is kind of an old post, but I was researching the idea of coating my bare rotors with engine enamel. Would applying enamel be worth the work for a better sealing blower? I'm assuming here the thickness of the enamel would come into play, but will clearance become an issue as long as I don't glob it on the rotors? Im also unclear if I would have to "rough" up the rotors for the enamel to stickl. So what Im really looking for here is all this possible and if it is, is it worth the time?
    Thanks for the help,
    Phil

  7. #7
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    Quote Originally Posted by Phillio99
    I know this is kind of an old post, but I was researching the idea of coating my bare rotors with engine enamel. Would applying enamel be worth the work for a better sealing blower? I'm assuming here the thickness of the enamel would come into play, but will clearance become an issue as long as I don't glob it on the rotors? Im also unclear if I would have to "rough" up the rotors for the enamel to stickl. So what Im really looking for here is all this possible and if it is, is it worth the time?
    Thanks for the help,
    Phil
    Phil,

    Don't even think about it....for starters you will need to press the rotors off the gearset shafts and then you have to figure a way to keep the coating evenly applied and make it stick. Then you've got to get the rotors pressed back onto the shafts while keeping them correctly scycronized (this it where it's probably hitting the dumpster).

    Your way better off just buying a late model rotor pack. I'm told that the ones from a GTP blower will bolt right on, but don't know that for a fact.

    David
    91 SC AOD 4.2..2.3 Whipple........10.92 @ 126.70
    93 SC AOD 347 Turbo.................10.04 @ 138.99
    My Garage

  8. #8
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    Oct 2004
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    Indy, IN
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    Reply

    Thanks Dave, wow what a downer, the dream is dead. Thanks again.

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