360 Magnum flexplate / balancing experts !

ValerianMagnum

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Hi guys , my duster 360 magnum ( crate ) needs to have the trans rebuild so i was wondering since i have several trans laying around ( all for 318/360s LA ) what can i do if i want to put a reverse valve body 904 on my 360crate to finish the season ? Theres all kind of infos and theories but im kinda lost , i had this issue in 2008 and i had a b&m flexplate for my 727 and my cuda had a 5.9 magnum and a 4 speed trans , never played with 727 and 904 for a 360 magnum since then ! Any part number , infos ? Thanks guys !
 

Howard1784

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No expert here. I have a a 380 hp magnum with a 904 rmvb. I have a weighted high stall converter as well since the engine is externally balanced. The key is welding the weights on the converter or getting the correct flex plate so you dont have a hellacious vibration
 

jbc426

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I'm a bit confused as to what you have going on, but I do know that 5.9 Magnums have extra balancing weights on the flex plates and harmonic balancers. 5.2 Magnums are neutrally balanced and have no additional weights on the balancer or flex plate.

I had to oblong one hole in the flex plate for my torque converter to bolt up to the flex plate. The torque converter was neutrally balanced for both.

200R4 3 (Medium).jpg
 

66 Valiant wagon

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^^^
What they said. Use the Magnum flexplate that has weights.
Also be aware that the 904 is a different length than the 727 so you may have driveshaft issues.
Good luck!
 

Mopar44134

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Here are a few pictures of the 5.9 flex plate vs. a regular flex plate. The 5.9, one bolt hole is off a little bit. If i remember right, @318willrun hogged out his to run on his drag truck. Check his you tube channel, bombcycle series.

20220709_122446[1].jpg


20220709_122420[1].jpg


20220709_122239[1].jpg
 

Jarlaxle

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Also be aware: the Magnum and the LA 360 are both external balance, but it is a DIFFERENT balance!
 

Brooks James

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Summit has been saying b and m. 360 magnum to flexplate is out of stock for a long time. B and M discontinued their 360 mag to 904 flexplate. The only place I could find one is Mancini Racing, $250.
It is designed to work with a neutral balance converter and a balancer that has OEM specifications.
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