Another OHV M90 build

[Dono]

Thanks! That coil bracket looks pretty intricate. Nice install for sure. I doubt mine will come out anywhere as nice as that. Does help give me ideas though.

[phix-]

I'll draw you some specs if you want? its not very complicated, unless you get fancy with coil pack tray. Just to let you know, without it I would start to misfire possibly.. after heavy heavy activity which is about 1hr+ of sliding around in a parking lot.

[Dono]

If you have specs, sure!
Then I would have a fighting chance of bending one up.
Without them, Id spend endless hours cursing, trying to get it right.

[rocket 5979]

Originally Posted by Dono

I think I was lucky. blades look good, no pitting visible. snout has a fresh oil change. spins smoothly. It was on the supercoup forum. Ebay is expensive for this stuff.

on the pulley, I must have been looking at pulleyboys specialized pulleys. They were 75.00

I seen your post about getting the M90 blower on SCCOA and decided to hop on there to see what prices I could find just for the heck of it. My original plan was to go to the local JY and take one off of a SC there, but it is a little cold out and they usually sell those blowers for the same price anyways. I had a local guy PM informing me he had one available and would let it go for $75 and would drive it up to my house this morning. Shoot, why not? Very cool guy and the blower was in real good condition. I immediately tore it completely apart getting it ready to do the port and exterior cleaning on it. I was sort of surprised how quickly I found something close to me. I have done porting on the Lightning M112 blowers before so I am used to having the cases of these Eatons apart but I forgot how bad that gear oil smells after it has some mileage on it. Phew!

[jd4242]

Originally Posted by rocket 5979

I seen your post about getting the M90 blower on SCCOA and decided to hop on there to see what prices I could find just for the heck of it. My original plan was to go to the local JY and take one off of a SC there, but it is a little cold out and they usually sell those blowers for the same price anyways. I had a local guy PM informing me he had one available and would let it go for $75 and would drive it up to my house this morning. Shoot, why not? Very cool guy and the blower was in real good condition. I immediately tore it completely apart getting it ready to do the port and exterior cleaning on it. I was sort of surprised how quickly I found something close to me. I have done porting on the Lightning M112 blowers before so I am used to having the cases of these Eatons apart but I forgot how bad that gear oil smells after it has some mileage on it. Phew!

Man i cant find the 3800 m90 under $250;(

[Dono]

The guys over at SCCOA seem pretty good. I guess we have to remember that these superchargers are from the 1970's. Im glad my postings are helping others from time to time.

Im not going to touch mine porting wise, as I have fear of decreasing performace. Besides, my brain can only handle so much at once.

Did you take any pictures of what you changed? Did you have to pull the blades to do the job(What about timing them on re-install?)? Im also not inclined to pull the blades or pull the snout apart unless suddenly there is a new requirement to do so.

I'll be away in Florida with the family on Friday, so hopefully when I get back there will be a new tb waiting for me.

So Rocket? Whats your plans for the M90?

[rocket 5979]

Originally Posted by Dono

The guys over at SCCOA seem pretty good. I guess we have to remember that these superchargers are from the 1970's. Im glad my postings are helping others from time to time.

Im not going to touch mine porting wise, as I have fear of decreasing performace. Besides, my brain can only handle so much at once.

Did you take any pictures of what you changed? Did you have to pull the blades to do the job(What about timing them on re-install?)? Im also not inclined to pull the blades or pull the snout apart unless suddenly there is a new requirement to do so.

I'll be away in Florida with the family on Friday, so hopefully when I get back there will be a new tb waiting for me.

So Rocket? Whats your plans for the M90?

The blower will need to be disassembled before you can port it. The rotors are VERY high tolerance to one another and to the inside of the main rear case so you don't want shavings getting where they shouldn't be. If your rear main case rotor bearings are still good then just tape them up real well so that no shavings get in them while porting. If they are already all messed up then just press them out and press in new ones that cost roughly $20.00.

The blower is comprised of 3 main sections. The snout assembly, the middle plate/bearings/rotors, and main rear case. Once you empty the oil from the front gear housing just take all the bolts out holding the 3 pieces together. Then take a rubber mallet and tap the snout housing off. It might take a few good raps so don't be shy. The snout will have a plastic coupler that allows the snout shaft to drive the "driven gear" in the blower. Once that is all out of the way then you will need to tap the middle plate/rotor assembly loose. This can only take a few small raps or it can take some real good ones too. I usually do a few real good taps around the case parting line and then get a flat head screwdriver in there an just lightly pry on each side widening the gap. Make sure not to scratch the mating surfaces between the 3 main sections as these seal either oil in or boost inside the blower. Once you get them apart about 1/4" then you can slowly and gently slide the middle plate and rotors assembly out of the rear case. You will be left with an empty blower case with those bearings I previously mentioned need to be taped up. From here is where you would start porting the blower inlet and outlet.

The rotors don't have to be retimed because they never separate from the middle plate and gears since it is all one unit that is pressed together. I have a bit of experience with these blowers so I would prefer to take them all apart to asses any issues before it is all bolted up and even harder to get to; especially considering how old these are and likely how many miles are on them. Rebuild kits go for about $80 for these so I figure that a good refresh is just good preventive maintenance to ensure I shouldn't have to pull the blower again in the future. This stuff goes hand in hand with the porting since the whole thing has to be apart anyways. Still, I can understand if you would rather not chance it.

I originally was going to do a custom twin turbo system on my 4.0 X Sport with those twin Garrett T25's that I had rebuilt about a year ago. Then I decided that since I plan to turn this truck into an offroader eventually that it would be more beneficial to have more off-idle torque of a positive displacement blower. Sure, I will probably be giving up 50hp on peak but it is not like I am building a racer anyways. So before I deployed last year I decided to sell those turbos to help fund the Eaton project. Now that I am back in the US I can start piecing things together. This will be a total bare bones build using stuff that I already have and parts that I fabricate to absolutely minimize cost. I will be building all of the manifolds, fuel system, intake system, etc.

[Dono]

Looking forward to seeing what you do with your Sport Rocket. Are you going to do anything to the sohc before you add the fi? It looks like there isn't really much available for those motors in the cam dept unless you go custom.

[phix-]

Alight, seems I can't find the original drawing I had with numbers and such but here is what the just.

The base is cut from the original coil-bracket and welded to heavy gauge sheet. The top mount is easy because it bolts onto the a/c compressor. The mount that goes to the exhaust mani. was guesstimated to about the 3/4 point. To create a second piece was made, bolted to the mani. and then welded the 2 together while in the truck.

[Dono]

Ugh.

That's the thing for me. No welder, or welding experience. No heavy metal experience either. If I cant cut it with tin snips, and use screws, I don't do it.

Yup, I can see my brackets looking like a child made them.

[phix-]

if I find measurements you can take an old coil bracket to a machine shop and tell them to build to spec. That is what I did for my air filter adapter (modified k&n fipk) to 90mm MAF. Which is just filed and re-drilled holes and the internal diameter bored out to just a tad larger than the MAF.

[Dono]

Maybe I'll swing by the graveyard and get an old bracket off a junker. Then I have a starting point. I don't want to modify any stock parts, just in case I need to put it back to near factory (Never know, might get in an accident, and want the blower back for a new(er) explorer).

Thanks phix, I hadn't put much thought in to the brackets for supporting components till now.

[phix-]

I have a spare coil pack bracket somewhere from my parts collection. I went your route and didn't modify stock (except for when I tried to dremmel down my stock composite air box) to fit 90mm MAF. needless to say that didn't work out.

[rocket 5979]

Originally Posted by Dono

Looking forward to seeing what you do with your Sport Rocket. Are you going to do anything to the sohc before you add the fi? It looks like there isn't really much available for those motors in the cam dept unless you go custom.

No I am not even bothering with upgrading anything on the stock longblock. Stock pistons, rods, cams, block, and heads. Very cheap build and looking to stay under the $1k mark for the entire supercharger project.

[Dono]

considering the sohc already flows way better than the ohv, I can see why. The sohc gets expensive to add high end parts to the motor. $ per horsepower is by far the greatest going your direction.
I can hardly wait to see what parts you have lying around and how you piece everything together.

Today, a bung is getting welded in to my exhaust. I'll then be able to install the wideband O2 sensor and gauge. At least its a start.

[phix-]

Believe it you could have got away with a wideband in the o2 bung after the cat. James, can tune it out of the PCM.

[Dono]

Interesting. I thought it had to be before cat. After the cat is probably easier. I'll see what the exhaust guy says.

oops......So your saying, just change the O2 sensor that's after the cat to a Wideband O2 sensor?

[rocket 5979]

Originally Posted by Dono

Interesting. I thought it had to be before cat. After the cat is probably easier. I'll see what the exhaust guy says.

oops......So your saying, just change the O2 sensor that's after the cat to a Wideband O2 sensor?

Do it before the cat not after. Putting it afterward can skew the readings a bit. Just keep it simple and have another bung welded in pre-cat like you had already planned.

[Dono]

Originally Posted by rocket 5979

Do it before the cat not after. Putting it afterward can skew the readings a bit. Just keep it simple and have another bung welded in pre-cat like you had already planned.

Done. Leaving right away to have it installed.

[rocket 5979]

Originally Posted by Dono

I can hardly wait to see what parts you have lying around and how you piece everything together.

Here are a few pictures of my blower after I disassembled it that should give you a little better idea of how it all goes together.