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1970 390 flexplate |
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5121 |
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Posted: May/09/2012 at 8:46pm |
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Are they? The flexplate from my '70 Machine looks the same as the one from my '69 AMX.
-Steve-
Edited by Rebel Machine - May/09/2012 at 8:46pm |
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amx39068
Supporter of TheAMCForum Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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I had two 68/69 service replacement blocksm one NOS and one used, and both had the correct 68/69 deck height, were balanced correct for the 68/69 model year and had the correct pistons, rods and crankshaft for 68/69. The 70 service replacement block was a different block and used the taller block for all ther 70 390 and 401s but should have the correct internals for whatever years it replaced.
What may be your case however is that someone unknowingly used a later service replacement block that was not correct for your year at some time in the car's life and swapped the earlier balancer and flex plate without realizing they are different than the ones that go with the earlier engines. For all you know, you could have a 401 lurking under the hood and the only way to tell is to pull it out and drop the pan to see what crankshaft and rods are actually in the block. |
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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69amxr
AMC Apprentice Joined: Jun/23/2011 Location: MI Status: Offline Points: 119 |
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thanks for the confirmation. I am assuming they are balanced differently. My AMX has a 1970 service replacement engine and I am guessing they used the original 1969 flex plate as I have a noticable vibration at highway speeds. I have narrowed the source down to the trans or flex plate.
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amx39068
Supporter of TheAMCForum Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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they are different
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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69amxr
AMC Apprentice Joined: Jun/23/2011 Location: MI Status: Offline Points: 119 |
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One more question along this same line. Is the flex plate from a '69/390 the same as the flex plate for a '70 390? are they interchangeable?
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amx39068
Supporter of TheAMCForum Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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Upon rereading the OPs original posting, I stand corrected but I would imagine getting the stud holes properly lined up so the converter is positioned perfectly from center will be a real PITA plus you would wan to drill the new stud holes equidistant from the old ones in either direction so as to not cause any extra stress points that might crack if the new holes are too close to the old holes. |
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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RedX
AMC Fan Joined: Jan/31/2011 Location: Alliance NE Status: Offline Points: 8 |
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Thanks everyone. I thought drilling was possible. Didn't think about welding. Could use a copper or brass 3/8" rod to protect the "good part" of the hole during the welding process. I installed the new nuts with the blue loctite. Will try that first before pulling tranny. Wish me luck.
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390spirit
AMC Addicted Joined: Jun/28/2008 Location: U.S.A. Status: Offline Points: 1849 |
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i took a F/P that was intended to be used with a 727 and drilled holes to make a TH400 converter fit it and mounted it to my 70 390 and it has worked great for 2 years now.
Yes it can be done! |
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bbgjc
AMC Addicted Joined: Nov/24/2009 Location: No.VA Status: Offline Points: 1665 |
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You could also weld the elongated part closed. A little welding wire, a little grinding and you're done. Probably quicker than drilling new holes, which would have to be correctly/exactly spaced or the flex plate will be out of true and will cause all kinds of issues.
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whizkidder
Supporter of TheAMCForum Joined: Mar/03/2008 Location: North Georgia Status: Offline Points: 2972 |
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I don't think he's changing the orientation of the plate to the crank -- he's changing the orientation of the converter to the plate. If the converter is neutral balanced it shouldn't matter.
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Ron Frost
marne1ancient @ gmail.com 910 nine two two 0563 "There is no limit to what a man can do, so long as he does not care a straw who gets credit for it. Charles Montague |
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