5.9 Magnum MPI swap flywheel idea

[DionR]

I've been debating about swapping a 5.9 MPI Magnum into my Duster, but one of the things holding me back is the flywheel. I would want to stick with my 4 speed OD, so the flywheel is a must. I was hoping that the stock 5.9 flywheel had some kind of bolt on tone ring, but I finally found a picture that shows it machined into the flywheel. I'm betting there is some extra steel there so they have something to machine, which is part of the reason that the magnum flywheel is so heavy, beside the extra weight from the additional diameter.

I got to thinking about trying to find a way to either sandwich the stock magnum flexplate between the crank and a 130 tooth flywheel, or maybe stitch welding just the tone ring from the flexplate to the back of the flywheel. I suspect that the flexplate would need some clearancing to get it to sit flat against the flywheel, and maybe stitch welding it would be the only option. If it could be made to sandwich between the crank and flywheel, it would only push the flywheel out a bit, and if that was too much then I could add a spacer between the bell and block to match.

In theory, this would get me a 130 tooth flywheel with the tone ring so I could run the mpi, but without a 38# flywheel hanging off the end of my crank plus saving me from having to find a bell housing that would fit both the 143 tooth flywheel and my A833 OD. I know what I need to fit the 143 tooth flywheel, I just don't want to have to track it down.

I know that the balance still needs to be correct, but hopefully the flexplate weights could be retained so that would be a non-issue.

Has anybody else thought about this, or tried something like it? Anyone see a reason it wouldn't work?

I know people buy the 143 tooth flywheels and machine them to fit, but that sounds expensive and you would still have a heavy flywheel due to the extra material for the notches to make the tone ring.

Any thoughts? Am I nuts?

 

[fzmax]

We're in the same boat. I'm swapping a T56 into my Dakota using a Quick Time Bellhousing. Of course the bell only works with a 130 tooth flywheel. Bruce at Modern Driveline is going to be selling a billet steel one, I'm first on his list.

He also tried to machine a 143 tooth flywheel down and install a new starter ring, but there seems to be in issue finding a factory flywheel that runs true enough. If you have a line on someone that can do this, please let me know and I'll be right on that.

Using a flexplate with the flywheel would take about a 1/4 inch spacer between the two and may push the flywheel back too far for the starter to properly engage and there may also not be enough splines on the input shaft.

Of course moving the CPS to the damper would eliminate the need for the tone ring. That is going to be my last resort as it would involve making a mount for the pickup, extending the wires and fabbing a new tone ring.

Didn't they use a 143 tooth flywheel with pre-Magnum small blocks in some trucks? Finding that bellhousing may be challenging, but that should work for an 833.

Finally you could probably get one from Keisler, but I have no idea what that would cost.

Please update this post when you get somewhere and I'll do the same. I've got about $2500 into this swap so far and until I get a flywheel, my truck isn't going anywhere.

 

[3406pk]

Please don't weld a flexplate to a flywheel. That would be a possible disaster with the weld causing cracking and a flywheel explosion. Even if this is not a high rpm deal there is still a chance of welds breaking and causing problems.

 

[DionR]

Using a flexplate with the flywheel would take about a 1/4 inch spacer between the two...

Why a 1/4"? Because that is as close as it comes to nesting? Is there material that could be removed to get it to nest without a 1/4" spacer?

I figure the flexplate doesn't need to be complete as it wont be carrying any load, it just needs to be strong enough to keep the tone ring stable at high rpms.

 

[DionR]

Please don't weld a flexplate to a flywheel. That would be a possible disaster with the weld causing cracking and a flywheel explosion. Even if this is not a high rpm deal there is still a chance of welds breaking and causing problems.

Didn't think about that. I was hesitant to suggest welding on it, but not for a good reason. But that there is a decent reason.

What about some ears that would extend out and use the clutch cover bolt holes? Not sure if there is enough room in the bolt hole for a bolt from both sides, but maybe some extra long bolts from the back acting like studs on the clutch side of the flywheel and nuts to bolt the clutch cover on.

I would ask about adding some small screws to hold the tone ring on, but that would require some machining and I am trying to avoid that.

 

[fstfish66]

what about a bell housing from a dodge ram, manual trans ??

 

[DionR]

what about a bell housing from a dodge ram, manual trans ??

As I understand it, an 89-91 D100/D150 bell would allow me to bolt up my A833 OD trans, and would fit the 143T flywheel, but I would like to avoid both.

A Dakota (AX15) bell would allow me to bolt up my R154 5 speed, but then I have to cut my floor and I don't want to do that yet (ever?). Even then, I would like to avoid the 143T flywheel (if possible).

 

[fstfish66]

check mancicni or hughes and se if they have a fly wheel for your needs,, some one at either of those places may have a blue print to re drill a LA motor 360 fly wheel to balance it to the magnum,,

 

[charger70]

I have a very good friend that has done this to put a 96 Magnum in his 70 Duster.
He used a Magnum flywheel and had it machined down, then knocked the ring gear off his LA flywheel and had it pressed onto the cut down Magnum piece. Then had the flywheel drilled for the pressure plate.
One of the pressureplate holes gets slightly into the bottom of one of the timing notches but apparently had no effect cause it's been running just fine for 5 years.
This way he was able to keep the original bellhousing.

 

[fzmax]

Why a 1/4"? Because that is as close as it comes to nesting? Is there material that could be removed to get it to nest without a 1/4" spacer?

I figure the flexplate doesn't need to be complete as it wont be carrying any load, it just needs to be strong enough to keep the tone ring stable at high rpms.

Yes, that is about as close as it comes to nesting. In the picture below you can see if you removed the edge of the flexplate it would sit closer, but there is still a gap there. You can also see in the second picture the one flywheel bolt that comes close.

 

[fzmax]

I have a very good friend that has done this to put a 96 Magnum in his 70 Duster.
He used a Magnum flywheel and had it machined down, then knocked the ring gear off his LA flywheel and had it pressed onto the cut down Magnum piece. Then had the flywheel drilled for the pressure plate.
One of the pressureplate holes gets slightly into the bottom of one of the timing notches but apparently had no effect cause it's been running just fine for 5 years.
This way he was able to keep the original bellhousing.

Can you tell me where he had that done? I've been unable to find someone local that can do this. The flywheel is the last piece I need for my swap.

 

[DionR]

Yes, that is about as close as it comes to nesting. In the picture below you can see if you removed the edge of the flexplate it would sit closer, but there is still a gap there.

Great pictures, exactly what I was hoping for! Thanks!

I'm not sure it would be an issue to cut the flexplate down until it fit. From what I've been able to tell, the notches on the flywheels are right up against the back of the flywheel itself, so as long as the sensor wasn't going to be hit by the flywheel (or the end of a bolt or something), I bet it would work fine.

This is a v6 flywheel (below) and it appears to be under cut under the pressed on ring with the notches. But the 5.9 ones are cut right into material cast as part of the flywheel.

I guess another idea would be to knock the tone ring off the above flywheel and then see if the 5.9 flexplate would sandwich behind it without interference between the weights on the flexplate and the back of the flywheel. Assuming that the flange for the tone ring on the flexplate would fit where pressed on tone ring sits now.

That would at least allow me to use a 10.5" clutch without machine work, but I would still need a different bell.

Here is a link to the post where I found that. http://www.jeeps-offroad.com/f41/engine-swap-bellhousings-4740/index7.html#post251292

Another thought might be to grab the v6 flywheel, machine the outside down to fit a 130T ring gear and bolt it up with the 5.9 flexplate sandwich between the flywheel and crank. It already has the 10.5" clutch pattern, so the only machining is the od, and it's pretty thin there so maybe it would be less expensive as well. I would also save the cost of balancing it as the flexplate would take care of that. In some ways it isn't much better than starting with a 5.9 flywheel to begin with, but in sure seems easier.

 

[fzmax]

The 5.2 flywheel appears just like the V6 one pictured except the tone ring has single cutouts evenly spaced around it.

The concern I had about cutting the edge off the flexplate would be the tendency for the edge to flare out as it spun. I am assuming that edge keeps it from expanding.

The other concern I had about using the flexplate behind the flywheel is that the centering register won't fit very far into the flywheel anymore and I wouldn't want to rely on the bolts to keep it centered. Of course if it would work not only I could stop waiting for the billet flywheel to be machined, but I could use the aluminum one in the picture.

For my truck I want to use the SFI approved bellhousing with the T56 or else I'd hunt down one of those truck bellhousings I mentioned above. If you can find one that would probably be the easiest thing for you.

 

[DionR]

Here is the back of a 5.9 flywheel from the napa website. No press on ring, but now that I look at it again, it does look to be stepped like the v6 and 5.2 flywheel.

I would be curious to see how an early flywheel and a crank position sensor would look together on a magnum block. Maybe just some measurements, even just how far the sensor is from the back of the block. Shouldn’t be hard to figure out if the sensor would interfere with an earlier 130T flywheel.

I guess you would have to measure the crank register and see how much overlap would be left after sandwiching the flexplate. I wouldn't worry about it if there is enough to center the flywheel before bolting it down. My only concern would be getting it centered, and if the crank register would do that, the bolts will hold it there, not a problem.

I see your concern about trimming the flexplate down, but I don't think it will move. Might look up the formula's and see what kind of force there would be there, just out of curiosity though. What's the od of the flexplate?

 

[fstfish66]

knocking off the starter ring and turning down the fly wheel; sopunds like the best deal,,and i would think you wouldnt throw off the balance of the fly wheel doing it that way,,

 

[DionR]

I think the best bet for me is going to be to find a bellhousing from an early v6 Dakota with an A535, a flywheel from a later MPI v6 Dakota, and a flexplate from a 5.9 Magnum.

The Dakota A535 bell should allow me to bolt my A833 OD to the back of the 5.9 Magnum (with a small modification) and run a 143T flywheel, but it probably won’t allow an 11" clutch (which is fine with me).

The MPI v6 Dakota flywheel might need to be neutrally balanced, but then I should be able to bolt my 10.5" Centerforce clutch up to it without any other modifications.

After I knock the tone ring off the flywheel, the flexplate should bolt up and give me the proper balance for the 5.9 Magnum, as well as the tone ring for the computer. This part is still kind of iffy, though.

If money were not a problem, I would agree that turning down a 5.9 flywheel would be the best bet; provided I could find someone who could do it (fzmax said he couldn't get it done).

If the flywheel already had a neutral balance, the only machine work would be the one bolt hole that is off on the bellhousing.

 

[fstfish66]

not sure where the idea of using a flex plate and fly wheel came from,,,the flex plate is balanced for a convertor,,and mounting the fly wheel to the flex plate is going to move the fly wheel out farther away from the crank im not so sure the balance would be correct,,,and you would have to do some adjusting on the clutch fork for proper throw out bearing travel just my 2 cents

 

[DionR]

not sure where the idea of using a flex plate and fly wheel came from,,,the flex plate is balanced for a convertor,,and mounting the fly wheel to the flex plate is going to move the fly wheel out farther away from the crank im not so sure the balance would be correct,,,and you would have to do some adjusting on the clutch fork for proper throw out bearing travel just my 2 cents

The idea came from trying to find a cheap way to use a 130T flywheel with Magnum MPI setup. The computer needs to see the tone ring that is on the flywheel and I was hoping to not have to buy a 143T flywheel and associated 11" clutch and big bellhousing (see the first post).

The theory was that if a flexplate would sandwich between the crank and flywheel, I could use the tone ring on the flexplate to run the computer, but still keep my small flywheel and 10.5" Centerforce clutch. That hasn't shone much promise.

Still in question is whether or not the crank lip is tall enough to center the flywheel with the flexplate behind it. I was hoping the 1/16" (or 1/8") of material in the flexplate wouldn't upset the clutch and fork relationship. If it does, then a similarly sized spacer between the bell and block should fix that right up. That's what they do with the 5.7 Hemi to fit the crank offset difference.

The flexplate carries the balance weight for the motor, that's why I thought I would use a 5.9 flexplate. The converters on the Magnum motors are neutrally balanced. Don't see why it would matter if there was a converter with a neutral balance or a flywheel with a neutral balance behind a flexplate with the correct inbalance for the motor. Also, I did find out that the v6 flexplate has no weights, so in theory, the v6 flywheel would also be neutrally balanced.

So, the parts list outlined above should be easy to find and should bolt together without any real machine work involved. I found a flywheel locally for $27, a flexplate for $12 and a bellhousing for $50. Bonus that I wouldn't have to even pull any of it.

BTW, there are 130T flywheels for 5.9 Magnums, but they are just early 360 flywheels with the correct inbalance for a 5.9 Magnum. They don't have the tone wheel for the computer.

 

[lhearold]

I think it may be easier to find a starter gear with the correct tooth pattern instead of afro-engineering a bunch of stuff on the flywheel. Thats the only reason for needing the different flywheel anyway. Don't you think???

Larry

 

[DionR]

I think it may be easier to find a starter gear with the correct tooth pattern instead of afro-engineering a bunch of stuff on the flywheel. Thats the only reason for needing the different flywheel anyway. Don't you think???

Larry

Actually, both the 130T and 143T flywheels have the same tooth pitch, the only difference is the number of teeth and the diameter of the ring gear. Both use the same starter, so no the ring gear isn't the reason for the different flywheel.

The reason is the need of a tone ring for the computer.

 

[fstfish66]

ok so the idea is you want to use the computer and injection,,,kool

i agree a spacer like in al hemis would fix the mis match,, i have a early red ram hemi and it uses a spacer all hemi cranks are longer out the back,,, i see your thinking now,,,,yes i agree it should all come together,,you may have to rework your tranny cross member mount

 

[DionR]

,,you may have to rework your tranny cross member mount

Hadn't thought about that, thanks!

Hopefully 1/16" or 1/8" wont be a big deal.

 

[fstfish66]

Hadn't thought about that, thanks!

Hopefully 1/16" or 1/8" wont be a big deal.

you may be able to E-LONGATE the tail shift mounting holes in the steel part of the cross member mount,,,if its much more then that weld a new plate to the top of the mount plate and redrill,,,

 

[DionR]

FYI, there might be a work around on this issue.

Just noticed that the notes for the MPI kit that Mopar Performance has for the 390 hp crate motor notes that a flex plate P4876706, a Magnum flywheel, or a DUAL TRIGGER DISTRIBUTOR is required.

Search for pn P5153731 and read the text. It might say "available spring 2007", but that is related to the kit, not the distributor (I think). The current MP catalog I have doesn't reference spring 2007, so I am assuming it is related to the kit.

Not sure which distributor it is, but I know that the lean burn systems sometimes had dual pickups, but I also know that later on the TBI motors had a Hall effect pickup like the FWD motor 2.2/2.5 used. Not sure if it was a dual trigger or not.

My assumption is that with a dual trigger, the distibutor could be made to read the crank position for the computer. Don't know what (if anything) would need to be done to make it work, though.

Anyone else know anything about this?

Figured I'd also post this in the engine section.

 

[fzmax]

That is very interesting. I did get an email and some pictures of my new flywheel so it's getting close. Hopefully I'll talk to him tomorrow and get more info or a firm date.