318 to 340

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7

73 gld dstr

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Hey guys
I am building a 340 to put in my car that has a 318 in it. The 318 is a 73 model and the 340 is a 72 model. Are these balanced different (internally or externally)? If they are do I need a new torque converter?
Thanks
 
Hold up there! Prior to April 1 72 the 340 was internally balanced after that day they were externally balanced. That said, while you are building the 340 you can make the later ones internally balanced.
 
1970Duster said:
Hold up there! Prior to April 1 72 the 340 was internally balanced after that day they were externally balanced. That said, while you are building the 340 you can make the later ones internally balanced.
Click to expand...

AH HA! i thought all 72 340s are internally balanced....not trying to steer anyone wrong.
 
Unless you have first hand knowledge and history of the 72 340...I would physically check to make sure it is a forged steel crank...
 
Take a look at your harmonic balancer on the 318-if the one on the 340 is wider it is externally balanced.Check on the price to get it internally balanced-if it is a externally balanced engine-in some places it is better and not much more to go with another crank,especially if you have to turn the old one.Make sure of what you have before you put out the money.
 
d5667 said:
Take a look at your harmonic balancer on the 318-if the one on the 340 is wider it is externally balanced.Check on the price to get it internally balanced-if it is a externally balanced engine-in some places it is better and not much more to go with another crank,especially if you have to turn the old one.Make sure of what you have before you put out the money.
Click to expand...

340 cast crank balancer will have "For 340 Cast Crank Only" stamped on it....
 
Do you already have all the parts to build it. If not, maybe buy a forged crank for it.

If you already have a cast crank and it's externally balanced, buy a flexplate for that engine, easy fix.
 
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