Quick flexplate question.

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Sweetjones

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I'm having a heard time finding an off the shelf converter with the right balance weights on it. I have a mildly built 340 an 727. My question is that I see these B&M flex plates that are balanced for a 340 so do they just bolt in place of the factory flex plate and you use a neutrally balanced converter?
 
B&M 10230 - B&M Flexplates forged crank neutral balance flexplate

B&M 10235 - B&M Flexplates 340 cast crank....weighted flexplate
 
I'm pretty sure it's forged crank. The motor was already built when I bought it so I'm not 100% on that.
 
Snap a pic of the harmonic balancer and post it here! That will tell the crowd what you're working with, and steer you to the correct flexplate! Forged needs neutral balance!
 
It's not the factory harmonic balancer I'm 100% sure on that. Lol when I get off work I'll go check it out and atleast try to get a part number off it. So suppose it is a forged crank and I get the B&M neutral balance flex plate do I still have to get a weighted (balanced) converter?
 
Call, and talk to Drew at street and strip performance, here in Louisville, Ky (502) 969 1500. I had a similar problem a few years back with a 340 cast crank flex plate. He's been drag racing Mopars for 30 years plus. I'm sure he can help you. I'm almost certain that a cast crank 340 uses a neutral balance flex plate as well. Because the torque converter is the balancing end of the crank. As the externally balanced harmonic balancer does the front end. But call to make sure.
 
Sweetjones said:
It's not the factory harmonic balancer I'm 100% sure on that. Lol when I get off work I'll go check it out and atleast try to get a part number off it. So suppose it is a forged crank and I get the B&M neutral balance flex plate do I still have to get a weighted (balanced) converter?
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If its a forged crank, and you buy the B&M 10230 neutral balance flexplate, you can run any neutral balanced converter! Same goes for the cast crank...if you buy the 10235 offset balanced B&M flexplate, you can run any neutral balanced converter! All you need to find out is if you have a cast or forged crank and buy the corresponding flexplate! Geof
 
cosgig said:
If its a forged crank, and you buy the B&M 10230 neutral balance flexplate, you can run any neutral balanced converter! Same goes for the cast crank...if you buy the 10235 offset balanced B&M flexplate, you can run any neutral balanced converter! All you need to find out is if you have a cast or forged crank and buy the corresponding flexplate! Geof
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You sir have just saved me a lot of head ache!!! Thank you!
 
1sttvbn said:
Call, and talk to Drew at street and strip performance, here in Louisville, Ky (502) 969 1500. I had a similar problem a few years back with a 340 cast crank flex plate. He's been drag racing Mopars for 30 years plus. I'm sure he can help you. I'm almost certain that a cast crank 340 uses a neutral balance flex plate as well. Because the torque converter is the balancing end of the crank. As the externally balanced harmonic balancer does the front end. But call to make sure.
Click to expand...

Yea I know all about street an strip. Good to see a local on here! I'm tryin to get my car ready to run trophy class at ohio valley. Lol
 
Since the engine is not original/unopened, you really have no way of knowing how it was balanced. I've seen some machine shops internal balance an externally balanced engine, and visa versa. The only way to be sure is to bring the old and new flexate to a reputable machine shop and have them matched, balance wise. I hope this helps. Eric L
 
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