flexplate ?

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rbkt65

rbkt65

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5.9 magnum w/904 or 999 low gear set w/lockup convertor. which cost effective flex plate to use. several choices as follows. atp z-332, b&m 10239, pioneer fra486. is that crankshaft weight you add between flex plate and crank for the 5.9 magnums? so many choices. what is flex plate of choice. i even have a stock mopar one. 5.9 has the 2 pc balancer. the 1 that the pulley bolts on the balancer not the 1 pc cast. tia.
 
I used the ATP Z332. I was running the factory EFI with a 904 transmission. This flexplate has the proper weight required for the 5.9 Magnum, which is different than the 360 LA weight.

My 5.9 originally came with the crank pulley bolted to the balancer, but it was bad and I ended up buying a later version that has the pulley and balancer in one piece. I couldn't find a standalone balancer that I was sure had the correct Magnum balance. Only the Magnum 5.9 had the one piece setup, so that's what I went with.
 
The B&M 10239 flexplate and QuickTime RM-531 bolt-on balance plate are both for LA 360s, which is a different balance than a 5.9 Magnum.
The ATP and Pioneer flexplates are replacement versions of the factory unit. The factory plate (as well as the ATP/Pioneer units, I would imagine) need one of the convertor bolt holes elongated to fit the 904 convertor. Easily done with a round file. Just be sure your convertor is a neutral balance unit (318) and not one with the balance weight from an LA 360.
 
autopar3000 said:
I used the ATP Z332. I was running the factory EFI with a 904 transmission. This flexplate has the proper weight required for the 5.9 Magnum, which is different than the 360 LA weight.

My 5.9 originally came with the crank pulley bolted to the balancer, but it was bad and I ended up buying a later version that has the pulley and balancer in one piece. I couldn't find a standalone balancer that I was sure had the correct Magnum balance. Only the Magnum 5.9 had the one piece setup, so that's what I went with.
Click to expand...
the PRW Race SFI Ballancer comes with the weight for the magnum. That is what i have on my 2000 360 magnum engine i have in my 91 dakota sport
 
mopar65 said:
the PRW Race SFI Ballancer comes with the weight for the magnum. That is what i have on my 2000 360 magnum engine i have in my 91 dakota sport
Click to expand...

Thanks, I'm looking at installing some underdrive pulleys so I'll probably have to get one of those PRW units.

When I mentioned I couldn't get one without the pulley I really meant I couldn't get one locally, same day. The story on this is that I bought a new balancer (no integral pulley) and when I finally got the car going it had a bad vibration. Turns out the balancer I bought was for a 5.2 even though it was in a box that had the part number for the 5.9 balancer. Either a factory screw-up or some guy before me bought a 5.2 then bought a 5.9 and returned the 5.2 in the 5.9 box. Either way, I was left needing a balancer right away and the only ones they had locally had the integral pulley.
 
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