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Original Message
What I'd do
By Ross - 08/23/2001 7:15:13 AM; IP 12.75.103.101
First as said by Mel, watch the front for a wobble (bent crank snout, bad balancer ring, etc.)

Without hearing it I assume its hitting on all 8, but make sure you dont have one dead cylinder, a skip would be a good shake

After that I would pull the inspection cover and turn the motor over by hand and look to see if there is a weight on the flexplate. Maybe there is and there shouldnt be with a 390

After that, assuming no luck, I'd pull the pan and look at crank numbers. 1U, 1UB, or the unlikely 1UA would tell you that you have an externally balanced crank and you need a weighted flexplate

Finally, if it was a 390 crank with a 390 flywheel, and it wasnt skipping. I'd pull the motor down and see whats bent or mismatched. Good luck
This thread, so far...
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Collapse <a href=../ForumFE/reply.aspx?ID=7759&Reply=7759><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor7759" onclick="return false;">'66 390 Internal Vibration</a>&nbsp;-- <font color=#0000ff>Paladin, <i>08/22/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=7759', contentMargin: 60, icon: $('anchor7759') }); </script>  '66 390 Internal Vibration -- Paladin, 08/22/2001
Collapse <a href=../ForumFE/reply.aspx?ID=7761&Reply=7759><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor7761" onclick="return false;">The wrong damper won't make it shake.</a>&nbsp;-- <font color=#0000ff>Dave Shoe, <i>08/22/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=7761', contentMargin: 60, icon: $('anchor7761') }); </script>  The wrong damper won't make it shake. -- Dave Shoe, 08/22/2001
 RE: Dampner may not be the problem -- Mel Clark, 08/22/2001
 RE: '66 390 Internal Vibration -- BOB HOPKINS, 08/22/2001
Collapse <a href=../ForumFE/reply.aspx?ID=7777&Reply=7759><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor7777" onclick="return false;">RE: '66 390 Internal Vibration</a>&nbsp;-- <font color=#0000ff>Ray, <i>08/22/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=7777', contentMargin: 60, icon: $('anchor7777') }); </script>  RE: '66 390 Internal Vibration -- Ray, 08/22/2001
Collapse <a href=../ForumFE/reply.aspx?ID=7781&Reply=7759><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor7781" onclick="return false;">RE: '66 390 Internal Vibration</a>&nbsp;-- <font color=#0000ff>Mel Clark, <i>08/22/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=7781', contentMargin: 60, icon: $('anchor7781') }); </script>  RE: '66 390 Internal Vibration -- Mel Clark, 08/22/2001
 Not exactly. -- Dave Shoe, 08/23/2001
Collapse <a href=../ForumFE/reply.aspx?ID=7792&Reply=7759><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor7792" onclick="return false;">Internally balanced 428</a>&nbsp;-- <font color=#0000ff>Ross, <i>08/23/2001</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=7792', contentMargin: 60, icon: $('anchor7792') }); </script>  Internally balanced 428 -- Ross, 08/23/2001
 RE: Internally balanced 428 Revisited -- Mel Clark, 08/24/2001
What I'd do -- Ross, 08/23/2001
 First Thing I'd Check -- Skip C., 08/23/2001
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