340 sb 1972 - external balance

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360duster

360duster

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Hi Guys,

yesterday i visited my brother who´s working on his 69 dart, Engine is out at the moment. The car came originally with a 273, now has got a 340 from 1972 with a cast crankshaft, external balanced (weighted balancer in front). The Trans and converter is still the one used with the 273 - is this balanced correct? Do the external balanced cast crank 340´s use a weighted flexplate / converter? There was no vibration or sth., just want to be sure.

regards

Michael
 
yup must have a blanced converter either weights on the converter or find a weighted flex plate,,,,
 
just incase you dont know,,,the current 5.9 360 magnum motors also require a weighted converter or flex plate,,,these are not the same balance as what that 340 needs,,

the old LA 360 also uses a weighted converter or flex plate,,but i do not know if the 1972/1973 cast crank externally balanced 340 motor uses the same converter,,,i would hope it would be that easy,,but knowing ma mopar it might not be,,,i would think that a converter shop would have a chart for this information
 
each externally balanced engine takes it own balancer and flexplates...
 
i saw that B&M sells a flexplate especially for the cast crank 340´s, so i know the balancing is different from the magnums and 360´s.

We´ll see what´s done to the engine, seems that somebody put new pistons in it, maybe they did a rebalance too - i have to check.

greets Michael
 
I feel your pain on this, I'm a long time 340 guy, and purchased a prepped 360 block ready for a stroker kit and I couldn't come to terms with putting all the externally balanced flywheels, dampner, etc. on. I used the 4.060 j.E pistons and put them in a 20 over 340 block and bought a 3.51. stroke steel crank from ma-mopar. I just protest the externally balanced shxx. I have seen too many people have the same problems you have, buy not knowing this and create a wicked vibration and wipe out there bearings.
Glad you knew enough to ask questions and figure it out, and are taking care of it.
 
If you are looking for a flexplate, let me know which one you need. I have a stack of different external balance FP's.
 
360duster said:
i saw that B&M sells a flexplate especially for the cast crank 340´s, so i know the balancing is different from the magnums and 360´s.

We´ll see what´s done to the engine, seems that somebody put new pistons in it, maybe they did a rebalance too - i have to check.

greets Michael
Click to expand...

to reblance that 340 to an internally balanced motor,,you could switch to a steel crank,,or a 318 crank,,or a 273 crank,, or the cast crank could be balanced internally,,,
 
highwaystar said:
I feel your pain on this, I'm a long time 340 guy, and purchased a prepped 360 block ready for a stroker kit and I couldn't come to terms with putting all the externally balanced flywheels, dampner, etc. on. I used the 4.060 j.E pistons and put them in a 20 over 340 block and bought a 3.51. stroke steel crank from ma-mopar. I just protest the externally balanced shxx. I have seen too many people have the same problems you have, buy not knowing this and create a wicked vibration and wipe out there bearings.
Glad you knew enough to ask questions and figure it out, and are taking care of it.
Click to expand...


You wouldn't have needed to use external balance flywheel etc on a 360 stroker, stroker cranks are internal balance arent they?
 
not everytime, you can get what you want or prefer. Personally i prefer the internal balance, so no worries about different weighted flexplates, converters, dampers etc. Just use neutral balanced stuff.

Thanks guys for all the information, i will tell my brother to check twice before doing some racing this season.....

regards Michael
 
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