Differences

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--- techtalk:ref:svcproc26 [2020/03/04 04:58]
hippysmack [Lightning Heads]
+++ techtalk:ref:svcproc26 [2020/03/04 05:59]
hippysmack [Thunderstorm Heads]
@@ Line 121: / Line 121: @@
 S heads and the older (pre-rubber mount) SE heads, 96-98 Buell S1 heads, 97 Buell S3 heads, 97-98 Buell M2 heads and Buell Blast heads are the same. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=715370)) \\
 These are what we call "Lightning" heads. \\
-cc chamber with a 10° squish shelf, 1.715/1.480 valve sizes, the old low floor, squared off bowl ports like all the hemi heads etc. \\
+cc chamber with a 10° cast in squish shelf, 1.715/1.480 valve sizes, the old low floor, squared off bowl ports like all the hemi heads etc. \\
 All 1200S motors came with flat tops just like every other Evolution Sportster. \\
@@ Line 132: / Line 132: @@
 The problem with those heads was the way in which they added the material. When you just add material to a chamber like that, you shroud the valves. \\ Looking at the chambers, you see a whole lot of material around the valves. That obstructs low lift flow. \\
+====== Thunderstorm Heads ======
+Two years after the Lightning head, HD came out with the Thunderstorm head. \\
+In the Thunderstorm, they went back to 67cc , allowing them to unshroud the valves and a 15° cast in squish shelf. \\
+They paired it with a domed piston to get the compression up to 10:1. \\
+They also improved the ports and went to larger valve sizes (1.810" / 1.575"). This setup is head and shoulders better than the Lightning setup. \\
+The angled squish bands direct the fuel being squeezed out of the squish bands more directly at the flame front. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206)) \\
+But the way it's done in the Thunderstorm, it's really rough. Since it's cast in, it's uneven. \\
+Typically from the factory the clearance is .050" or more, and that makes the squish band largely ineffective anyway. \\
+Thunderstorm heads are obsolete now. \\
+They could be machined nice and even, but there's a huge overhang around the perimeter. \\
+So to machine it, typically .035"-.045" had to be taken off the deck, sometimes more. \\
+Below is an example of before and after machining. This is much better with a nice even and consistent squish clearance. \\
+But cutting the deck this much has some side effects, like less valve to piston clearance. \\
+As well as potentially forcing the customer into short or adjustable pushrods. \\
+It also typically makes the chamber too small, forcing us to open it up in other areas. \\
+Also notice how there's not a whole lot of surface area. This squish band is effective up to about a .125" tall dome. \\
+Anything higher than that and the dome goes past the squish band. \\
+|  Stock Thunderstorm Heads ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206))  |  Thunderstorms as Machined ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206))  |
+|{{:techtalk:ref:svcproc:thunderstom_chamber_by_aswracing.jpg?direct&300|}}|{{:techtalk:ref:svcproc:thunderstorm_as_machined_by_aswracing.jpg?direct&300|}}|
+====== Buell XB/04XL Heads ======
+As delivered, they have flat squish bands with a 62cc chamber. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206)) \\
+This lets you toss them on over flat tops and have a squish band with lots of area and 10:1 compression. Not a bad way to do it. \\
+If you want to angle it, it's not a problem, you've got lots of material to work with. \\
+You can make the squish band as big or small as you want. \\
+You can make it match the piston you're using exactly, do relief cuts with the rest of the material to help overlap flow if you want. \\
+You can do all this without excessive deck milling and all the problems that come with it. \\
+The stock valves are the same sizes as the Thunderstorms, 1.810" intake and 1.575" exhaust. \\
+The springs and guides can support up to .550" lift safely, though, versus .500" for the Thunderstorms. \\
+The ports are actually a little better than the Thunderstorms. \\
+The Thunderstorms were a major step forward from the Lightning/Screaming Eagle heads, but the XB/04 XL1200 heads are even better. \\
+|  Stock Buell XB Heads  ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206))  |  Machined XB Heads ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206))  |
+|{{:techtalk:ref:svcproc:buell_xb_heads_by_aswracing.jpg?direct&300|}}|{{:techtalk:ref:svcproc:buell_xb_heads_as_machined_by_aswracing.jpg?direct&300|}}|
 ====== Compression Ratio ======

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