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Cobra Forums
2013-14 Shelby GT500
10% Lower + 2.5 Upper on a '13
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<blockquote data-quote="Jam421" data-source="post: 15601128" data-attributes="member: 110985"><p>My upper 2.4 pulley makes 2.5-2.7psi boost. Way up on redline it might hit 3. The 10% crank pulley advertises makes 3-4psi boost likely more consistent delivery . I'm not sure if guys actually get 4psi. Both make HP but the lower is supposed to bring Tq closer to the HP. My Tq with upper was about 30 less than HP.. The guy's car I mentioned above with the lower 10% had about a 35 spread between the two. SOoo...go figure ! </p><p>With the upper I had belt slip on the stab. Metco tensioner definitely helped as instead of just wrapping the top of the small pulley it held the belt under/around the side as well increasing surface contact dramatically. I also treat my SC belt occasionally with a belt spray. The lower pulley actually decreases belt slip simply because it's larger diameter.....way more belt to pulley contact. </p><p>If I could buy a new or undamaged condition stock 2.67 upper pulley for my Trinity I'd likely take the 2.4 upper off and have the crank installed. </p><p>I should put a WTB ad on the forums.<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" />->).</p></blockquote><p></p>
[QUOTE="Jam421, post: 15601128, member: 110985"] My upper 2.4 pulley makes 2.5-2.7psi boost. Way up on redline it might hit 3. The 10% crank pulley advertises makes 3-4psi boost likely more consistent delivery . I'm not sure if guys actually get 4psi. Both make HP but the lower is supposed to bring Tq closer to the HP. My Tq with upper was about 30 less than HP.. The guy's car I mentioned above with the lower 10% had about a 35 spread between the two. SOoo...go figure ! With the upper I had belt slip on the stab. Metco tensioner definitely helped as instead of just wrapping the top of the small pulley it held the belt under/around the side as well increasing surface contact dramatically. I also treat my SC belt occasionally with a belt spray. The lower pulley actually decreases belt slip simply because it's larger diameter.....way more belt to pulley contact. If I could buy a new or undamaged condition stock 2.67 upper pulley for my Trinity I'd likely take the 2.4 upper off and have the crank installed. I should put a WTB ad on the forums.(:->). [/QUOTE]
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2013-14 Shelby GT500
10% Lower + 2.5 Upper on a '13
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