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flywheel balance

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    Posted: Sep/24/2014 at 7:03am
I am going to swap out my auto for a manual transmission. The flexplate was balanced with the engine. Can you get the new flywheel to match the already balanced flexplate or is it even necessary? Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote uncljohn Quote  Post ReplyReply Direct Link To This Post Posted: Sep/24/2014 at 7:48am
AMC V8 engines were externally balanced from the factory requiring that the harmonic balancer and the Flex plate for automatic transmissions and the flywheel for standard transmissions be from an engine of the same displacement when replaced or as you are doing changing to a different transmission. 
The I-6 cars were internally balanced and the components used out side the engine are the same on pretty much all I-6 cars that were physically capable of being used used by directly bolting on to the engine. Thus making it a whole lot easier to do what you are trying to do. 
However if you are unable to located the correct flywheel from another engine for yours, a shop that does balancing is capable of rebalancing the wrong part for your engine so that it would indeed be acceptable. They just need to know the size of the engine you are going to bolt it on to and the year of it. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote cone Quote  Post ReplyReply Direct Link To This Post Posted: Sep/24/2014 at 8:48am
Thanks, it for a 360.I still  need to find a flywheel for it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Sep/24/2014 at 9:09am
You will need a flywheel for a 360. You will need to know if it's the pre-72 flat crankshaft, or the 72-up stepped crank. A good machine shop should be able to "match balance" the new flywheel to your old flexplate.

Bob
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ebojan Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 9:38am
Hey guys, 

I am in the process of rebuilding my amc 390. I have already spent the money on the rebuild kit, and am in the balancing process. The shop called me and said they can not get he fly wheel to mount on the crank without some movement....therefore they can not balance it. 

Is it because they don't have the exact bolts that were removed? 

Have you heard of this issue before? 

Any ideas, insight, suggestion would be greatly appreciated. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 9:53am
Ebojan,

I suppose it's possible if they are using the same size threaded bolt but with a different shank that there is some movement. SBC flywheel bolts are the same as AMC. Maybe a Ford or Chrysler bolt has a different shank diameter.

otherwise,

Read Tufcj's post, that is most likely your problem.

The bolt holes match up for the 71 and earlier flywheels with the 72 and later flywheels, but the aligning method is not just the bolts, the bolts orient the flywheel to locate it in the correct "clocking" position, but the back of the crank-flange determines the concentricity of the two. You need a flywheel for the year engine you have.

Armand

Edited by White70JavelinSST - Oct/28/2014 at 9:56am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 12:18pm
This make perfect sense...you have a 72 up flywheel that center on a step in the crank, trying to mate to a flat flange crank.  As others in this thread have said you need a flat flange flyweel, it will interface with the Outside Diameter of the crank flange and will not be "loose".  And as Armand has said above, the bolts orient the flywheel in the proper clocking to make sure weight is in right position.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ebojan Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 3:32pm
Ok so I will dig through the shelf and see if I can find the flywheel bolts I removed this past summer. Then I should be good. Thanks for the help guys! 


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Post Options Post Options   Thanks (1) Thanks(1)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 3:40pm
Ebojan

Many people (including me) and I believe the TSM doesn't recommend re-using flywheel bolts. It's OK to use the old bolts for engine balancing but it is strongly recommended to use new bolts when putting the flywheel back in service.

Are you sure you have the correct flywheel?

Armand
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ebojan Quote  Post ReplyReply Direct Link To This Post Posted: Oct/28/2014 at 3:55pm
Hmmm ok. Yeah it is the one I took off of it. Never had any issues prior. It used to run great. 
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