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techtalk:ref:svcproc26 [2020/03/04 04:55] hippysmack [Machined Squish Band] |
techtalk:ref:svcproc26 [2020/03/04 05:47] hippysmack |
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| ====== Lightning Heads ====== | ====== Lightning Heads ====== | ||
| - | 1200S 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. \\ | + | 1200S 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. \\ | These are what we call "Lightning" heads. \\ | ||
| - | 62cc 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. \\ | + | 62cc 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. \\ | All 1200S motors came with flat tops just like every other Evolution Sportster. \\ | ||
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| 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. \\ | 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. \\ | ||
| + | |||
| + | {{:techtalk:ref:svcproc:thunderstom_chamber_by_aswracing.jpg?direct&300|}} ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206)) \\ | ||
| + | |||
| + | 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 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. \\ | ||
| + | |||
| + | {{:techtalk:ref:svcproc:thunderstorm_as_machined_by_aswracing.jpg?direct&300|}} ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=2206)) \\ | ||
| + | |||
| + | ====== Buell XB/04XL Heads ====== | ||
| + | |||
| ====== Compression Ratio ====== | ====== Compression Ratio ====== | ||
