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304 vs 360 Crankshaft

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waggygreen View Drop Down
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    Posted: Aug/04/2021 at 11:32am
Can anyone confirm what I have been told is that the AMC 305 and the amc 360 crankshaft are interchangeable.


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mstrcrftr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mstrcrftr Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 11:39am
yes they are.  just make sure that you use one that fits your flywheel-flexplate. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 12:19pm
AMC 304 and 360 crankshafts

are identical crankshafts year by year.

70 and 71 have a different flange than the 72 and later crankshafts.
70 Javelin SST, second owner, purchased 1972
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Post Options Post Options   Thanks (0) Thanks(0)   Quote waggygreen Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 12:47pm
Would they need any balancing difference then each other or is everything the same plug and play

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SC397 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 1:07pm
Originally posted by waggygreen waggygreen wrote:

Would they need any balancing difference then each other or is everything the same plug and play

Yes they would need balancing. They are not balanced the same.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote waggygreen Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 1:17pm
Thank you for all the help.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 5:08pm
Originally posted by SC397 SC397 wrote:

Originally posted by waggygreen waggygreen wrote:

Would they need any balancing difference then each other or is everything the same plug and play

Yes they would need balancing. They are not balanced the same.

When you say that, I presume you just mean that you need to use the 360 harmonic balancer and flex plate, as far as I was aware, the crank itself is the same. 
I've finally given up drinking for good...........now I only drink for evil.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 5:22pm
Originally posted by westernred westernred wrote:

When you say that, I presume you just mean that you need to use the 360 harmonic balancer and flex plate, as far as I was aware, the crank itself is the same. 


Because the 360 pistons are bigger and weigh more, the 360 crank counterweights probably have less material drilled out so they are slightly heavier.   It's always best to have the entire rotating assembly balanced when mixing/matching parts.

Bob
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Edited by tufcj - Aug/04/2021 at 5:25pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 6:53pm
Just for reference I have 304 and 360 stock piston/pins/707 rods. The 304's are 1425g and the 360's are 1556g total.
A 707 rod - 686g and pin - 169g are the same for both.
I left out the decimal places as these are averages. pistons and rods can vary up to 4g each. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/04/2021 at 8:15pm
Originally posted by WesternRed WesternRed wrote:

Originally posted by SC397 SC397 wrote:

Originally posted by waggygreen waggygreen wrote:

Would they need any balancing difference then each other or is everything the same plug and play

Yes they would need balancing. They are not balanced the same.

When you say that, I presume you just mean that you need to use the 360 harmonic balancer and flex plate, as far as I was aware, the crank itself is the same. 

The crank itself is the same but remember, each rotating assembly was balanced individually regardless of cubic in size. 
No two are the same.
So regardless of the pistons and rods involved each engine needs to be rebalanced. Some Machinist leave the crank alone and balance the rest of the parts to match. Some do a combination of balancing the crank and rotating components to match.
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