Rotor pack/gear plate swap how to...

pablon2

Registered User
Well, it looks like I'll be swapping my rotor pack myself. I don't mind doing it, but hadn't planned on being the one to do it. As we all know, plans change. Anyhow, I am swapping late model coated rotors into my MPII. I have searched and found posts detailing similar swaps, but I feel they go into more detail and work than is needed for my situation (baking/freezing/pressing parts) and therefore I don't know which components of the process I need to follow and which ones are not necessary. I say this b/c I don't believe I need to replace any bearings/seals as my blower has only 75 miles on it since the MPII conversion/rebuild. SO, what I need to know is what do I have to do to merely swap the rotor pack/gear plate assembly? Do I need to replace any seals while doing this? (I'm working on a 75-mile old rebuild.)

Thanks in advance. :)
 
It's easy if that's all you are doing. Just take the snout off then with a rubber mallet gently tap the rotors. (this is the inch or so that the snout but up against.) You just need to do it enough to loosen the rotors up enough to get them to pull out. Then slide in the new ones, bolt up the snout (don't forget to line up the coupler, otherwise it won't go together) and fill up with supercharger oil. That's it. You don't even have to pull the pulley off. I would seal up the mating surfaces with some rtv sealant, just to keep everything nice and tight. Be careful though on the rotor side so you don't get any of that rtv into to rotors...not that it would really damage the rotors, but it's just better to keep as much as you can out of the rotor/case. Easy job and shouldn't take more than about 30 minutes to complete.
 
No need to do anything except swap the rotor pack and put some sealer on the case,then bolt it back together. Probably a good idea to let it dry overnight before adding the oil.

David

PS: I'm sure Sam means 30 minutes after the blower is off the car.
 
super red91 said:
Loctite 518 to seal the rotor pack, I got it from Napa ;)

Seal the rotor pack? Do you mean the 1" thick gear plate attached to the front of the pack? Can't I just use Ford gasket maker? Takes about 8oz to refill the SC correct? One more thing, dare I reuse the oil? It only has 75 miles of use or so on it.

P.S. David, luckily the SC is off the car.
 
Last edited:
David Neibert said:
PS: I'm sure Sam means 30 minutes after the blower is off the car.

Yeah...just the rotor swap...add another 20 minutes or so if you have to pull the supercharger off and back on...(I've probably gotten it down to that quick as many times as I've pulled it off...) :(
 
pablon2 said:
Seal the rotor pack? Do you mean the 1" thick gear plate attached to the front of the pack? Can't I just use Ford gasket maker? Takes about 8oz to refill the SC correct? One more thing, dare I reuse the oil? It only has 75 miles of use or so on it.

P.S. David, luckily the SC is off the car.

He's talking about sealing the plate of the rotor pack to the blower case on one side and sealing it to the oil filled snout on the other side. The side that seals to the snout isn't nearly as critical as the blower case side.

To prevent excessive clearance on the ends of the rotors (inlet end), you must not use a sealer that is too thick. I use RTV and spread out in a very thin coat, but the loctite mentioned earlier would be better.

I would also suggest test fitting the rotors before adding sealer and bolting it back together, to make sure the rotors turn freely. You will also want to recheck the rotors after bolting the blower together and especially after bolting down to the intake manifold to make sure it still turns freely.

In some rare instances where the rotor tip to case clearance is very close (less than .002) the slight amount of case distortion from bolting the blower down to the intake manifold will cause the rotors to bind. If this happens it will be necessary to use shim stock between the blower mounting bosses and the blower case stacked in amounts necessary to remove the distortion.

David
 
pablon2 said:
Thanks for the quick responses. Any opinions on reusing the barely used SC oil?

If it's still clean, I'm sure it will be fine. If you want an added measure of safety, strain the oil thru a clean cloth to remove any dirt or metal particles.

David
 
David Neibert said:
.....strain the oil thru a clean cloth to remove any dirt or metal particles.

David

I bet a pair of pantyhose would work. ;)

What's the torque setting for the SC housing bolts? I found the numbers for the mounting bolts for the SC, but not the housing ones.
 
Last edited:
pablon2 said:
I bet a pair of pantyhose would work. ;)

What's the torque setting for the SC housing bolts? I found the numbers for the mounting bolts for the SC, but not the housing ones.

Beats me...I just tighten them up about the same as I would any other bolt that size. I'm guessing mine are around 25 ft lbs.

David
 
Tickler said:
This mod is by far my favorite, please tell us the results afterwards.


If by results you mean HP gain, unfortunately there is no way I'll know as I am changing several things simultaneously. One thing I am doing differerently, b/c of the rotor pack change, is I'll be overdriving the MPII 15% instead of the planned 20% due to the increased efficiency, plus this will give me a place to step up to in the future (20%) if things pan out.

However, if by results you mean, how did it go for me, by all means I'll share what i hope to be my success story. I am having a time finding Loctite 518. I called two Napa stores and they couldn't find it. The third cross referenced Permatex (owner of Loctite) sealer 518-13, so I'll ASSume that is the same. The description of it is an anerobic gasket maker. More to come, can't wait to open 'er up.
 
Since there seems to be lots of interest in the coated rotor swap I think I might make a how to. I am currently helping my friend put a 94/95 sc on his 89. I did some porting on the blower and bought a set gtp rotors to put in it. So since its all apart I can take pictures along the way and make a how to. Ive also put the gtp rotors in my MPII so I have a clue as to whats involved.
 
When I had an MPII..I replaced the bare rotors with late model coated rotors and gained about 1.5-2.0 pounds of boost. With the MPIII I've got now I replaced the bare rotors with a set of ESM (High Speed Labs) coated rotors and also gained 1.5-2 pounds of boost.

So I would expect Pablon to get similar results. BTW, I think he's also doing the right thing by reducing the amount of overdrive.

David
 
super red91 said:
Since there seems to be lots of interest in the coated rotor swap I think I might make a how to. I am currently helping my friend put a 94/95 sc on his 89. I did some porting on the blower and bought a set gtp rotors to put in it. So since its all apart I can take pictures along the way and make a how to. Ive also put the gtp rotors in my MPII so I have a clue as to whats involved.


That sounds like a great idea. Maybe could have "sticky" potential? You hit on a good point, with coated rotor packs becoming available without the entire blower, this mod will become more frequent and the process will result in FAQs.
 
Well, the snout is off and I'm working on the rotor pack now. I noticed the shaft that goes into the spring has three wear marks on it from the spring. Is that normal wear and tear? One other thing, there is a cast shroud around the early-style gears, but not the new style. Is this normal or am I missing something?
 
Last edited:
Son-of-a-beaver!! :mad: :mad: Sometimes it seems like nothing goes easily the first time. I wondered why the parts wouldn't fit together nicely during my dry fit (thanks David for recommending the dry fit, it saved me here). I looked and noticed the freegin' alignment sleeves are in two different positions on the gear plate and the housing. So, I have to have the one that is wrong pressed out and placed in the correct spot. Or I may just machine the one hole to accept the sleeve and then add a sleeve to the plate's hole so it matches the existing machined hole in the housing. This wouldn't be a bad idea as it would then give me three sleeves. If not, would it hurt to not have a sleeve in a hole that was machined for it? I know that I sure the heck am not going to pound out the existing sleeve b/c I don't wanna compromise the mating surfaces. Damn, this gets me. Unless someone has a brilliant quick fix for this, I'll have to hand it over to my dad who is a tool and die maker/machinist. As has been the case with this rebuild...the saga continues. :cool:
 
Last edited:
The new rotors dont have the cast around the gears, dont know why but they just dont. Nothing to worry about.


The one alignment pin needs to be moved into the lower position. Use a vice and a socket that is about the same size as the pin and put a larger socket on the other side to press is out. Clean out the new hole and put some oil in it so when you press in the pin it goes in smooth.

We just finished putting my friends back together took pictures along the way, but the digital camera took a ~~~~ so we had to use a phone. Dont know how good the pics will come out but it should help.

I did some porting on the blower inlet/outlet (94/95 style) added the coated rotors and it makes a tad over 15psi with a STOCK pulley. The car (89 sc) has an intake, 75mm tb, ported/welded plenum, raised top, double ic, and a full exhaust.
 
Last edited:
Back
Top