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<blockquote data-quote="KBR" data-source="post: 16429853" data-attributes="member: 186018"><p>I found some alternator pulley math. </p><p> </p><p>Looks like with 4lb lower and 3.2 alternator pulley, we may be over spinning the alternator at redline. </p><p></p><p>3.5 may be better if running a 4lb ring...see below</p><p></p><p>RPM Calculator</p><p>An alternator needs 1800-2000 RPM at idle to make power and will make maximum output at 6000 rpm but will <strong><u>fail at 16,000 RPM</u></strong></p><p>@ 6500 rpm with 3.2 pulley = 17,468.75</p><p>@ 6500 rpm with 3.5 pulley = 15,971.42857142857</p><p></p><p>Measure Alternator pulley size (Metco recommended 3.2")</p><p>Measure Crankshaft Pulley Size (4lb ring 8.6")</p><p>The Ratio is 2:1 (8.6 divided by 3.2 = 2.6875)</p><p></p><p>To find MAX RPM: take your Max engine Speed (for example 6500 RPM) and multiply it by the calculated ratio (6500 x 2.6875) = 17,468.75 shaft RPM</p><p></p><p>To find IDLE RPM: Multiply Idle RPM x Ratio </p><p></p><p>PS my alternator is making noise but still charging. After researching J2Fab, Mechman, Nations...etc, I ordered one from Ken Miley jr.</p></blockquote><p></p>
[QUOTE="KBR, post: 16429853, member: 186018"] I found some alternator pulley math. Looks like with 4lb lower and 3.2 alternator pulley, we may be over spinning the alternator at redline. 3.5 may be better if running a 4lb ring...see below RPM Calculator An alternator needs 1800-2000 RPM at idle to make power and will make maximum output at 6000 rpm but will [b][U]fail at 16,000 RPM[/U][/b] @ 6500 rpm with 3.2 pulley = 17,468.75 @ 6500 rpm with 3.5 pulley = 15,971.42857142857 Measure Alternator pulley size (Metco recommended 3.2") Measure Crankshaft Pulley Size (4lb ring 8.6") The Ratio is 2:1 (8.6 divided by 3.2 = 2.6875) To find MAX RPM: take your Max engine Speed (for example 6500 RPM) and multiply it by the calculated ratio (6500 x 2.6875) = 17,468.75 shaft RPM To find IDLE RPM: Multiply Idle RPM x Ratio PS my alternator is making noise but still charging. After researching J2Fab, Mechman, Nations...etc, I ordered one from Ken Miley jr. [/QUOTE]
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