ballancing 360 crate motor

[Chryco Psycho]

Cool thanks guys, but is there a difference from 360 LA and Magnum on the weight needed to balance?

I am not sure on the Magnum engine but I believe it is also external balanced

[Chryco Psycho]

this is incredibly helpful , I have the Mopar Magnum engine book here & cannot find any reference for the balancing of the old & new 360

[71chally416]

The key is the Dampner. If it says "For externally balanced 360 only" then you need the weighted convertor or special flexplate or flywheel. There is no scenerio where they would use that with a neutral balance behind the motor. 

[Chryco Psycho]

but is the balance weight the same ?

[71chally416]

I believe so, front and back, but don't quote me. My Chally had a 360 when I bought it and when I took the tranny out it had a SFI flexplate with weights welded on and it had no vibration problems. I just removed the weights when I put the stroker in (it was internally balanced) and no problems. I've never had any other externally balanced motors though, so my experience is limited to that. I've always had forged crank motors.   

[71chally416]

You can get about any flexplate you need here and it looks like the Magnum takes a different plate than the gen 1 360>
http://chucker54.stores.yahoo.net/bm1.html

[boydsdodge]

I thought so.
If the P/O did not know this like most of us, I could see that he might have just put a first gen 360 flywheel in.
That would cause a problem, wouldn't it. I think it would.

[tactransman]

Flywheel /Flex Plate/Converter Balance

Magnum 360 (5.9) = 91 Gram Weight
Pre Magnum 360 =  120 Gram Weight

[Chryco Psycho]

That would do it

[71chally416]

I'm guessing the piston weights are different. I've seen those rebuilt factory short block Magnum motors call for neutral balance and the Pre-magnum 360 short blocks call for extenal balancing, so it depends on which one you use. The 360/408 crate motors say to use this weighted flexplate - P4876706 that looks like this>

 
 

[tactransman]

Every 5.9 engine Magnum or Pre-Magnum has to be externally balanced from the factory. The 5.2 magnum does not.

[moper]

I was going to say... Magnum crates have special flexplates and flywheels... If you can feel the vibration as you raise rpms without the car moving, it's the engine... If it's only while driving, it's driveline..