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Original Message
Not exactly.
By Dave Shoe - 08/23/2001 12:56:54 AM; IP 216.243.158.229
The 410, 428plain, all 428PIs thru 1970, and 428CJ thru mid November 1968 were all externally balanced at the flywheel only. These all had identical piston and rod weights, so they all got the same crankshaft and offset-balanced flywheel. The front half of these engines were internally balanced, so the damper was neutrally balanced.

In mid-November, the SCJ and CJ broke away from the crowd and got unique balances for several differing reasons. Invariably, the CJ is externally balanced only in the rear half of the engine (and kept the same flywheel balance as the 410/428), and the SCJ is externally balanced at both the rear and the front of the engine (and got a different flywheel balance than any other 410/428).

Note that the 428SCJ is what retired the 1969-427 production engine in November of 1968. With LeMans rods and looser-fitting cast aluminum pistons which were reinforced at the pin boss, this engine could hold together at higher revs than other 428s. Because of the heavier rods and pistons, the SCJ got a custom balanced flywheel, a counterbalanced crankshaft spacer to balance the front half of the engine, a high-RPM neutrally balanced vibration damper, and a custom-balanced crankshaft (marked 1UA).

The 428CJ then inherited the SCJ's stronger piston (however, with a snugger fit in the cylinder bore than the SCJ) as soon as it became available in mid-Nov 1968. This was a natural move because, unlike the 428PI, the CJ had the same dish volume as the SCJ. This heavier piston required the use of a custom balanced crankshaft, so in November of 1968 there were suddenly three crankshafts for the 428 which differed in balance only, the 1U (428PI), the 1UA (428SCJ) and the 1UB (the 428CJ).

After dyno-testing the SCJ in November, Ford apparently decided they could reinforce the new SCJ piston even more, so after updating the tooling, they came up with an even stronger version of the pin boss in late December. This revised SCJ piston weighed 20 grams more than the original SCJ piston, effectively obsoleting the two new 428 crank balances of November. Two newer 428 crank balances were created in late December of 1968 to balance the SCJ and CJ engines with the heavier version of the SCJ piston.

Shoe.
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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