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Old 09-28-2006, 09:31 PM   #1
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Default M-90 rebuilt questions.

Hi!

I was referenced to you folks from the Grassroots Motorsports board. They said you guys are the best when it comes to Eatons!

Anyway, I just picked up a dirt-cheap M-90 to rebuild & install on my 83 VW & had a couple questions. I searched & found some of the answers I needed, but here'* what I couldn't find:

I've pulled/pressed it most of the way apart, but I'm not sure how to get the rotors separated from the front of the rotor housing. Do the rotor shafts need pressed out of the twin gears on the front?

Is there any one vendor who has the cheapest prices on rebuild parts, or will I need to mix-n-match? Also, are any of the seals/bearings/oil *generic* enough that I might be able to find them at the local industrial supply house? I'm building this car for the GRM $2007 challenge so every penny counts!

Thanks!!!
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Old 09-29-2006, 12:03 AM   #2
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WOW. Ok, one of our members is a co-worker of mine at HP, and has an Eaton M45 on his Jetta, so you have some good support in that arena too. He'll probably see this in the AM and post.

My first question is what displacement is your motor? the M90 is probably WAY too big for you from what I know you MIGHT have for CC'* or Liters under the hood. An M45 might be more suitable, or on the OUTSIDE, maybe an M62. The M90 will cost you WAY to much in horsepower just to spin it. The 45 and 60 have smaller diameter rotors than the 90/112, making it take less power to spin up, and most VW'* I'm familiar with don't have the displacement for the 90. But we'll put that on hold until we find what motor you have.



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I've pulled/pressed it most of the way apart, but I'm not sure how to get the rotors separated from the front of the rotor housing. Do the rotor shafts need pressed out of the twin gears on the front?
Don't do it. I've rebuilt more Eaton'* on this Forum than anyone, and I rebuilt the first on this Forum. Leave those bearings between the rotor plate and rotors for life. Or pay someone with a factory jig like www.canadiansupercharger.com to do it for you. Replace the needle bearings in the case and rebuild the nosedrive ONLY.

www.rollingperformance.com will have everything you need except the sealant. It'* red gasket maker, and you can buy it in a small tube or a big tube from any GM dealer. Use nothing else, despite some saying you can use RTV. Use ONLY GM supercharger oil. No substitutes. You will need 2 bottles.
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Old 09-29-2006, 08:26 AM   #3
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Pete... nothing I can add here ...except that Willwren is extremely knowledgeable on SC'*. He'* done the homework, research and testing for the rest of us.

You are in good hands.
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Old 09-29-2006, 10:30 AM   #4
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Yeah, this is definitely too big for me, but for $50 beggars can't be choosers. Besides, the whole point of the GRM challenge is to be opportunistic & resourceful....but if there'* anyone interested in swapping my M-90 for an M-45/62, let'* talk!

The engine in the GTI is a 2.0L bottom end(under the stock JH 1.8L head)with a mild cam. I'm looking for no more than 10psi...more like 7-8 acutally...and I've calculated max flow(no boost)to be 260cfm at 7500rpm. I'd like a consistent 170-180hp, and with the other upgrades to the fuel system, the engine should be able to handle 220hp or so. Which should be fun in an 1800lb car.

The reason I was asking about removing the gears is that it appears there was oil leaking past those seals onto the rotors. Is this */c a core at this point, or is there another way to change them?

Thanks!
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Old 09-29-2006, 10:34 AM   #5
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Originally Posted by Pete Gossett
anyone interested in swapping my M-90 for an M-45/62, let'* talk!!
PM on way to keep topic on topic.
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Old 09-29-2006, 11:43 AM   #6
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Ok, Pete. I figured it was no bigger than a 2-liter. Even a VR6 is barely in the M62 territory. I'm pretty sure an M62 will even cost you horsepower just trying to spin it.

Greyhare here has a Neuspeed Kit with an Eaton M45 on his Jetta. It works well. And the 62 wouldn't have gained him as much. You've only got a little more than half the displacement we do.

Finding a donor M45 is going to be a real trick. Not many production cars ran them (any?). Your best bet would probably be a Gen2 M62 from 92/93, and a BIG pulley. Perhaps even bigger than the Gen3 2.8" pulley, but you'll have to be very careful about belt offset to choose your line of pulleys. There isn't a GM supercharger out there that will have the right pulley for you, so you're going to have to buy one. Will the M62 even fit under your hood, and run far enough back to line up with your belt path?

I'll call Greyhare and send him to this topic.
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Old 09-29-2006, 12:45 PM   #7
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The M90 is too big unless you go with a very well ported 16v head, 02A transaxle and wide sticky tires.

The M62 is what GM uses on the Cobalt. (Big pulley, 3"+ IIRC)

The M45 is good for ~200 to 220Hp at the crank. Most of us with the Neuspeed kit are running around 170 to 180Hp at the crank. The trick to getting more is an intercooler.

An M45 will probably be difficult to find but Bill'* suggestion of an M62 should work.
With a little head work and a good cam (Techtonics 260/26 it should be good for over 200Hp at the wheels.

Most people who have done this mount the blower in front of the engine. BBM does this with their Lysholm kit.

I see you have already tried the vortex. Search for "Eaton" in forced induction, archived content; there are allot of posts some may be useful.

What are you using for engine management and fueling?

Welcome to the club, you will find it very different from the vortex.
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Old 09-29-2006, 12:57 PM   #8
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Thanks!

Yes...much different from vwvortex. Thank goodness!

I'm running a G-grind cam & the intake/exhaust are port-matched, so I'm good there. Trans is a Scirroco 16V(2CY?)& I'll have plenty of rubber - looking at 235/45/13 race rubber. I'm running stock CIS, but I have the Audi WUR and Vac advance units already, and I'm buying a Volvo 240T fuel distributor - so I should be set there.

I've measured, if I take out the stock fan/shoud & switch to a front mounted pusher fan I'll have enough room for the M-90, so fitting an M-62 shouldn't be a problem.

I'll try the search using Eaton in the archived content of the 'tex.


So what about replacing the rotor seals on this M-90? Is it d.i.y. doable or does it need to be done by a pro?
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Old 09-29-2006, 01:11 PM   #9
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Pro with a factory jig. You can do the needle bearings in the case, and the nosedrive bearings and seals, but even I won't attempt the rotor plate bearings and seals again.
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Old 09-29-2006, 09:42 PM   #10
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So I have to ask - did you fail, or was it just a PITA?

I'm guessing the jig holds the rotors perfectly vertical on the press & prevents stress on the aluminum front plate?
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