4 speed flywheel

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1973dusterkid

1973dusterkid

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Going to look at a 4 speed with a 340 flywheel can I get a 340 flywheel to fit or 360 of do I need a 360 flywheel.When I did the engine swap in my duster I bought the plate to run a 318 tq converter on the 360 with a 904 trans.
 
You will need a 360 flywheel the 360 is external balance, and the 340 is neutral balance, so the flywheels are different , I bought one from 440 source for $99 it has removable weights so it will work with both internal, and neutral balance.
 
jtkaaa07 said:
You will need a 360 flywheel the 360 is external balance, and the 340 is neutral balance, so the flywheels are different , I bought one from 440 source for $99 it has removable weights so it will work with both internal, and neutral balance.
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Not 100% correct, the apr.1, 1972 the 340 became external balance so there is a 340 external balance flywheel. Just putting that out there.
 
1970Duster said:
Not 100% correct, the apr.1, 1972 the 340 became external balance so there is a 340 external balance flywheel. Just putting that out there.
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And its a different external balance than a 360 too. Only works for the 340.
 
1970Duster said:
Not 100% correct, the apr.1, 1972 the 340 became external balance so there is a 340 external balance flywheel. Just putting that out there.
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:prayer:Correct, forgot to mention that, Just a general reference for a person not experienced in this. I would recommend anyone doing a conversion ask a lot of questions, this is not just a plug and play job, different driveshaft , and lot's of small pieces that are easy to miss. I have done a couple, and it's a learning experience to say the least!
 
73AbodEE said:
your drive shaft will work
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Count the splines on the output shaft, if its a 26 spline the 904 yoke will work, if it a 30 spline you need a 727 yoke, which changes the length of the drive shaft you need. Mine has a 30 spline 727 yoke, and is 52 inches center to center on the u joints.
 
hi, the 340 flywheel can be drilled to the 360 balance required for it, mopar has a blueprint of it in their race manuals. I have drilled a few of those and they work !!!!! just food for thought.
 
Balance is as follows for small blocks.
273-318 neutral
340 steel crank neutral
340 cast crank external, different than 360
360 LA external
318 Magnum neutral
360 Magnum external, different than LA 360

As far as drilling a flywheel, if you are as much as a 1/2 a degree off on you measurements when you take the weight out, you have just throwed the entire balance of the bottom end.

McLoed makes a nice SFI flywheel that you can change weights on for any engine.
 
easiest way to tell an externally balanced 360 flywheel from a 340 unit, look at the counter-bore holes in the back of the flywheel, 3 holes=360. 2 holes=340 (external) no holes= neutral. Ive been told that 340's are whats called a "detroit balance" meaning the entire rotating assembly is balanced as a unit. so some flywheels accordingly are balanced to a specific rotating assembly, and may not work well with other units. hopefully someone else can back that up.
 

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hi, thats why you have a machinist with a milling machine do it!!! as far as being off, ones I done were right on the money!!! just food for thought
 
you can also get a weight that bolts between the crank and flywheel for 30$...fits really nice in the crevase too.thats what were doing on our demon.
 
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