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World's Fastest Street HD
Name: Josh
Back to basics....L vs. HD Pulley Combo's...Explained in Chart/Graph Form
Been a lot of discussion lately with pulley sizes and some people are still a bit confused on how the pulley ratios work.
HD's come stock with a 3.25" upper and L's come stock with a 2.93" upper. Both trucks come with the same size lower.
HD's stock are 6 lbs of boost and L's stock are 8 lbs of boost.
Aftermarket pullies are named for the boost increase they add on a Lightning, NOT a harley truck. A 6 lb'er adds 6 lbs to a Lightning, it does NOT add 6 lbs to a harley truck. The rough general rule of thumb has been 2 lbs less for a HD, but since its a ratio, this isn't fully accurate. From a generalized standpoint, boost is a linear function of blower RPM. More RPM = more boost. While up high this is not true because hot air is less dense therefore less boost, and low RPM its a bit different as well, the generalized ideal boost level vs RPM for the middle of the "s-curve" of boost vs RPM can be linearized.
http://www.nhtoc.com/vbforum/newthre...newthread&f=18
That thread was our sticky for a while, but with everything in text form for some its a bit harder to interpret. I took Ryan's approach and threw it into a chart and a table that should clear it up for everyone.
The first table is the calculations for pulley combos & net boost for L's vs. HD trucks
The second table is the pulley combos for least to most boost on any truck depending on the combo of uppers & lower's. So a 4 lower & L upper makes more boost than a HD upper and 6 lower, etc.
The chart is blower RPM vs net boost for the known L pulley combo's, and where the HD pulley combos fall into place at.
This chart and tables are up for discussion as I may have overlooked something, but PLEASE READ THE ENTIRE LIST OF ASSUMPTIONS & EXAMPLE ON THE RIGHT OF THE CHART BEFORE BRINGING UP DISCUSSION POINTS!!!
This will soon become a new sticky
M.HYDE: 2000 HD F-150 #0356 of 8197, Built 05/18/00, Bought 07/03/00, 700/784, 09.89@138.78
*Worlds Fastest Street HD: '08/'09/'10/'11/'12/'13****Worlds Fastest Eaton Powered HD: 12.19@112.48 11/17/07*
D.JEKL: 2000 HD F-150 #1552 of 8197, Built 06/20/00, Bought 06/25/09, 372/450, 13.75@099.46 (*SOLD* 10/15/11)
REPTAR: 2012 SVTF-150 #2893 of ????, Built 01/19/12, Bought 08/26/11, ???/???, 14.93@091.30
HASTIE: 2011 GT Mustang 5.0 6-Speed, Built 10/29/10, Bought 11/11/10, 392/352, 12.00@117.79 (*SOLD* 05/14/13)
BADGER: 2013 Explorer Sport 3.5L TT, Built ??/??/??, Bought 05/14/13, ???/???, 14.53@096.25
GEN.0L: 1985 XL F-150 w/'94 Lightning Donor Engine Swap, Holley Projection EFI, 03 HD Paint
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