360 flex plate

[3404spdfish]

ok guys. looking for info. short story is I have a 727 from my 340 I want to take that tranny and use on my brothers 360. I saw some dudes use a flex plate that is balanced for a 360 does that mean I can use the torque converter from the 340 or do I still have to buy the externally balanced torque converter for a 360, just trying to shave a few dollars off this build.

 

[318willrun]

Balanced flexplate on a 360 uses a neutral balanced converter. B&M makes balanced flex plates. Summit/Jegs/ebay has them for sale. So, in short, put a balanced flex plate behind the 360 and run a neutral balanced converter

 

[3404spdfish]

Balanced flexplate on a 360 uses a neutral balanced converter. B&M makes balanced flex plates. Summit/Jegs/ebay has them for sale. So, in short, put a balanced flex plate behind the 360 and run a neutral balanced converter

Word, that's just the info I was looking for, thanks man

 

[dewsky]

ALLRIGHT!!....I was wanting that info as well!!!

 

[Dartnut]

What year of a 340 are we talking about?
Some were internally balanced, and some were externally balanced.
Early ones were forged cranks and internally balanced and later ones ('mid '72 and all '73s) were externally balanced.
I would find out for sure about the one you have and go from there.
BTW, i have seen engines with the cranks swapped in an earlier or later casting date engine, so looking at the block casting date is not 100% accurate.
When you know for sure, give B&M a call and go with their recommendation.
JMHO.

 

[Bobzilla]

Previous suggestions are good but I would add that 360 LA balance is different than 5.9/360 Magnum balance. Just make sure you specify which one you are working with before choosing a flex plate, as they are not the same.

 

[3404spdfish]

What year of a 340 are we talking about?
Some were internally balanced, and some were externally balanced.
Early ones were forged cranks and internally balanced and later ones ('mid '72 and all '73s) were externally balanced.
I would find out for sure about the one you have and go from there.
BTW, i have seen engines with the cranks swapped in an earlier or later casting date engine, so looking at the block casting date is not 100% accurate.
When you know for sure, give B&M a call and go with their recommendation.
JMHO.

69 340 early date code

 

[3404spdfish]

the 360 block I am working with is a 74 pre magnum

 

[transman]

factory flex plates for MOPARS. Two sizes(depending on converter size, either 11" or 12"), two different crank mounting patterns. Used from 1962-up. On the 360, the converter had two weights each 1.62" x .75" x .380", for a total weight of 100 grams. On the 340, two small weights each .88" X .62" X .177". Hope this helps, along with the attached pdf. The 340 converter is not balanced for the 360, so either get as others have suggested, a B & M flex plate, or get a rebuilt 360 converter. The 340 converter stalls around 2400 rpm, and a 11" 360 converter typically will stall about 200-300 rpm less. Don't dump the 340 core, as they were and probably still are difficult to find. The converter shop I worked at all 340 converters were core in first, with NO exception.