Flex plate and converter

[jackie]

Let me see if I can get this straight. I have a 1965 Barracuda with a 1972 340 and 727. I pulled it out to check it all out. 340 had a steel crank , it was cracked. Replaced it with a stock cast crank. Rebuilt the engine and transmission. Changed the converter to 2500 rpm stall. It had a b&m flex plate and I reused it. The plate has both size holes for the converter. The converter had the big bolts in it. The new one has small holes. The small bolts only line up with the large holes. What plate do I need to get? I had to put it together to move the car. Now later just sitting I can’t remember if the converter has weights on it or not. I would guess I would remove weights, if any and swap the flex plate. Help if you can!

 

[toolmanmike]

You might have a messed up combination. I'll wait for the guys that have been there to explain.

 

[Professor Fate]

Let me see if I can get this straight. I have a 1965 Barracuda with a 1972 340 and 727. I pulled it out to check it all out. 340 had a steel crank , it was cracked. Replaced it with a stock cast crank. Rebuilt the engine and transmission. Changed the converter to 2500 rpm stall. It had a b&m flex plate and I reused it. The plate has both size holes for the converter. The converter had the big bolts in it. The new one has small holes. The small bolts only line up with the large holes. What plate do I need to get? I had to put it together to move the car. Now later just sitting I can’t remember if the converter has weights on it or not. I would guess I would remove weights, if any and swap the flex plate. Help if you can!

Oy vay...
Steel (forged) cranks are internally balanced. Was the cast crank you swapped in from a 340 or a 318? 340 cast cranks were externally balanced, and required specially balanced convertors and harmonic balancers. 318 cranks, whether cast or forged, were all internally balanced. Depending on what supporting parts you used with the crank swap and whether you had the assembly re-balanced, you have a potentially messed up bottom end that will give you nothing but grief.
The B&M flexplate you need to use is dependent on the combination of parts that are used- i.e. an externally balanced crank with a neutral balance convertor, an internally balanced crank with a neutral balance convertor, an externally balanced crank with a weighted convertor, etc. etc. They're all different, so we need to know what you've actually got in order to know where the issue is.

 

[jackie]

You might have a messed up combination. I'll wait for the guys that have been there to explain.

Oy vay...
Steel (forged) cranks are internally balanced. Was the cast crank you swapped in from a 340 or a 318? 340 cast cranks were externally balanced, and required specially balanced convertors and harmonic balancers. 318 cranks, whether cast or forged, were all internally balanced. Depending on what supporting parts you used with the crank swap and whether you had the assembly re-balanced, you have a potentially messed up bottom end that will give you nothing but grief.
The B&M flexplate you need to use is dependent on the combination of parts that are used- i.e. an externally balanced crank with a neutral balance convertor, an internally balanced crank with a neutral balance convertor, an externally balanced crank with a weighted convertor, etc. etc. They're all different, so we need to know what you've actually got in order to know where the issue is.

 

[jackie]

The engine was internally balanced at a machine shop. Balancer is supposed to be correct. He also had the flex plate. But I got the converter later. I think I just need the correct flex plate, but don’t know which one. Also if the converter has a weight on it, I need to just remove it? I am hurt at this time and can’t take it apart to see exactly what I have. But I would order the correct flex plate if I knew. Thanks