magnum matched to 904

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venomvpr900

venomvpr900

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I finish the overhaul of the transmission to today :cheers: I brought it home and plugged the torque converter in all was perfect. I then decided to check the flexplate bolt up before mounting motor and trans (good thing) the TQ converter and flexplate did not line up one hole is about 1/2 a hole off. I about threw it down the street, I grab the MP catalog and looked and I ordered the correct TQ converter. BUT MP tells you to order a flexplate with motor "must use" what they fail to tell you is there is 2 part numbers. one with symetrical lugs and one with offset so I guess tomorrow I will order the offset part number and hope it matched up on the TQ converter. I swear if MP would pull there heads out of their @** they might make some money to help the cause:angry7: Any way enough venting, My question is if I use the offset magnum flexplate which is balence for the engine and the MP TQ converter which fits 67-92 904 I will need to balence the TQ converter for 360 magnum MP offers a weight kit I can get but I am confused (probally not big surprise to some) the specs sent with the crate motor state....
"If you want to re-use a older converter, the you must remove any existing weights" then later on it states .... "flywheels and TQ converters are unique to the magnum 360 engine. do not use a flywheel or flexpalte/converter from any other engine unless it is re-balenced for the magnum 360. so the answer I'm looking for is do I need to removed weights from the MP converter then bolt it up or do I need to leave them on and install the MP weight kit to the converter. Sorry it's long this has got me pulling my hair out.
 
Ok I talked to the boys at Mopar this morning his answer was short and to the point "if the flexplate is weighted use a neutal balenced converter" how do I know if the converter is balenced neutral ? is this something and transmission shop could check ?
 
I ran into this issue puttin my Magnum engine in front of a 727.
If you have a trusty trans shop they certainly should be able to tell you.
If they can't they shouldn't be in business.
a good engine builder should also be able to tell you too.

There are 2 kinds of balance weights you might find on a converter.
First they balance all the converters removing imperfections due to manufacturing, there are small thin (postage stamp size) weights on the sides for that. Those are the ones known as "neutral balance" for internal balanced engines,-- or engines that have the balance weights on the flexplate.

Then to correct the engine balance issues they add larger weights to the face of the converter across from the flexplate.
Those weights could be on the flexplate or converter to correct the balance.

what converter are you using?
If stock, what engine was it used behind.
 
venomvpr900 said:
Ok I talked to the boys at Mopar this morning his answer was short and to the point "if the flexplate is weighted use a neutal balenced converter" how do I know if the converter is balenced neutral ? is this something and transmission shop could check ?
Click to expand...


If the TC is weighted you will see the weights on the front side. MOPAR Performance makes the Magnum flexplate with the correct weights for the 5.9 already on it. Its a symetrical mount (all holes equally spaced) and IF your 904 TC was for an internally balanced engine you will not see weights on it, the holes will be equally spaced and it "may" bolt up. Most of the TCs used with the Magnums were larger than the 904 TCs by about 1/2 to 3/4 inch so check it first.

Larry
 
It's a Mopar performance converter, it only has the small weights on the sides. So I should be good, I will check the new flexplate tomorrow and as long as it's weighted I should be ready to bolt them together. Thanks for the reply
 
Larry, I have the MP flexplate which is symetrical mount but it does not match a MP TQ converter that fits my trans. all the 904 sloted hubs are offset lugs
 
venomvpr900 said:
Larry, I have the MP flexplate which is symetrical mount but it does not match a MP TQ converter that fits my trans. all the 904 sloted hubs are offset lugs
Click to expand...

If its the symetrical mount with the ring around it with the holes for the CPS sensor then it should have the balance weights welded on the inside of the ring somewhere. Thats right since the slotted hub TC was for use on an externally balanced engine (late 340 or 360) But, if thats the case it would have the large block weights welded on the front unless its a new MP item and they didn't put the weights on because they expect the buyer to add them depending on the engine connected to it. Before I put the 518 tranny in my Dart I had a 904 hooked to my Magnum and if I remember correctly, 3 of the 4 bolts would go in but I had to drill the flex plate for the 4th one. It was about 1/4 inch off. I was using the weighted flex plate at the time. Seems that the offset is different on the 904 that the 518 but not by much. I think B&M makes a flex plate to match a magnum to a 727 tranny but I don't know about the 904.

Larry
 
all pre magnum converters and flex plates are off set mounting holes,,period,, it has nothing to do with internal or external balance,its just the way it was,,
i have not delt with a modern,magnum set up yet,,,,but im sure mp has a balanced flex plate to make your old style 904 and converter match up,, if not B&M has flex plates,, try jegs or sumit,,i doubt a local trans shop has any clue as to what your doing,,,
 
Ok the offset flexplate came in and is not weighted. I think I'm going to slot the MP weighted flexplate instead of welding weights on to the TQ converter. One I'm not to keen on welding on to the TQ converter and two the "detailed" instructions that come with the weight kit are clear as mud. I'll let ya know how it comes out
 
Slotted out the MP flexplate tonight - fits fine should be a go!!! to bad I'm going out of town this weekend or motor would be in :(
 
I dont aprove of slotting the holes in the flex plate. I know, its not my call but
I've seen flexplates and flywheels (GM) that were run for more than a few days with loose torque converter bolts. Result is oval or egg shaped holes. The bolts will never stay tight again.
If I couldn't come up with a correct fit I would fill and redrill the holes on size.
Just my 2 cents Good luck with it.
 
red fish i agree,, it owuld be a miracle if it never worked its way looose lock tight or not,,, the corect flex plate does exsist,,but thewelding the hole shut and redrilling is a great idea,,
 
I won't say that I disagree fstfish because I like to do things the right way, but in this case I'm willing to bend a little. I don't like the idea of welding on a brand new TQ converter $400 I would rather take a chance and have to replace a flexplate $50. I have the correct flexplate and weights for the converter if this doesn't work. I took very minimal material off flexplate about 1/8 of a inch on each of the four holes.
 
he didnt meen to weld on the converter,, he ment weld the hole on the flex plate shut and redrill in the proper location,,, the correct flex plate is available ready to bolt on,,sorry for the confusion,,
 
Yes the correct flexplate I have but it is not weighted to balence the magnum motor so you have to weld weights onto converter. No problems here just explaining the method of my madness
 
Yeah I meant correct the flexplate hole pattern. I have filled a hole or 2 in the crank pulleys without a major balance problem or any other problem. For that reason I was imagining you filled one or 2 holes. If you had to file most or all the holes ... :( . The directional load on a pulley is on way where the direction load on a flexplate is both ways.
 
I ran into this also on my Magnum engine swap. I just filed the one hole that was off added a little blue loctite to the bolts. Still working on the wiring for the EFI, so I haven't ran it yet. OG
 
I figured taking a little out of each was better than alot out of one. I'll just have to wait and see. If it ends up causing a problem I'll be swaping flexplates and adding weights. I'm confident it's going to be ok, maybe I'll try to get a few pics up
 
B&M use to sell a weighted flex plate for the LA 360 plat form,,weights already attached,,i would think they would have the same thing for the magnum plat form,,,its worth looking in to,,hope all works out wil be intresting to know how it turns out,,
 
B&M SFI flex plate P# 10241 was made for this application, but seems to be out of production. I got John Cope's last one a couple of months ago.The 93-95 360 Magnum Flex plate (asymetrical) should also work with a nuetral balanced TC.
 
I use the B&M Flex Plates ALL the time..I put them behind the Magnum Motors with 904/727 Trans and Vice/Versa..

The NEW B&M Flex plates for these applications have a Moon Shaped Cut-out on it to weight it...

I have had several of these over the years...
I went to one of my customers once that bought a TC from me.He wouldn't spring for the B&M Converter.He told me that the my Converter Builder welded the snout crooked.I got him ANOTHER one and he put it in and said it too took out the front seal..That my guy must be whacked in the head...So I go and look at the car.I get there and he had the large holes of the converter welded shut with plates over them...I said"Whats the name of that Plate?".He says Flex-Plate...I Said Yea...FLEX Plate meaning it WILL flex and is Made to Flex under Higher RPM applications.It was unable to FLEX so it would roll out the front seal continuously...
I have also had guys putting flexplates in and trimming the bolt holes and end up with a disaster...You might as well put a timebomb in there..The WEIGHTS are No Longer Correctly Balancing the Converter/Crank...You would be better off putting an Unbalanced FP on as to put one on that is UnCorrectly balanced..


SS
 
The only b&m flexplate for a magnum motor fits 727 transmissions only, all others are for pre magnum 360 motors, at least that's what I could tell by looking at their website
 
venomvpr900 said:
The only b&m flexplate for a magnum motor fits 727 transmissions only, all others are for pre magnum 360 motors, at least that's what I could tell by looking at their website
Click to expand...

The Small Ring is the same when used with the smaller Converter..That is the ones I use..

I'll have to get ya a Part #..

Drilling or Grinding on Flex-Plates is only looking for trouble...


SS
 
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