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techtalk:ref:svcproc26 [2020/03/04 05:59]
– [Thunderstorm Heads] hippysmack |
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techtalk:ref:svcproc26 [2024/01/22 21:42] (current)
– hippysmack |
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| The squish (AKA "quench") band refers to the area or areas, \\ where the piston comes very close to the cylinder head while passing through top dead center (TDC). ((http://www.hammerperf.com/ttcheckingsquish.shtml)) \\ |
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{{:techtalk:ref:svcproc:squish_band_3_by_aswracing.jpg?direct&400|}} ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) {{:techtalk:ref:svcproc:squish_band_by_aswracing.gif?direct&250|}} ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/89229-conversion-using-used-parts-where-to-go-from-here?t=715370)) \\ |
| Even though the fire has already been lit, these areas still contain unburned air/fuel mix as the piston arrives. \\ |
| The piston sandwiches the air/fuel up next to the head, causing it to "squish", and shoot out toward the flame front. \\ |
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| ====== Measuring the Squish Band ====== |
| ===== Indirect Method ===== |
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| You can use a piston height gauge to measure how far above or below the cylinder deck the piston is sitting at TDC. \\ |
| Then add that measurement to the gasket thickness. \\ |
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| {{:techtalk:ref:svcproc:1200-1250_squish_band_measurement_by_hippysmack.jpg?direct&400|}} ((drawing by Hippysmack)) |
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| ===== Direct Method ===== |
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| You'll be placing some soft material, such as .065" solder, onto the squish band area of the piston. \\ |
| (clay has been used for this also but it's not as accurate as using solder which won't change thickness) \\ |
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| * Write the measurements down to conclude and average the squish band dimension. |
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| Solder held with grease. ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) | Remove the heads to reveal how far the solder was compressed. ((photos by JohnK of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.php?p=3944070sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/132786-fixing-a-leaky-top-end-with-pics/page6#post2887799)) || |
| |{{:techtalk:ref:svcproc:squish_band_1_by_aswracing.jpg?direct&300|}}|{{:techtalk:ref:svcproc:checking_squish_1_by_johnk.jpg?direct&300|}}|{{:techtalk:ref:svcproc:checking_squish_2_by_johnk.jpg?direct&300|}}| |
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| Measure the compressed side of the solder pieces. ((photo by JohnK of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.php?p=3944070sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/132786-fixing-a-leaky-top-end-with-pics/page6#post2887799)) | Write the measurements down to conclude and average squish band dim. ((photos by JohnK of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.php?p=3944070sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/132786-fixing-a-leaky-top-end-with-pics/page6#post2887799)) || |
| |{{:techtalk:ref:svcproc:checking_squish_3_by_johnk.jpg?direct&300|}}|{{:techtalk:ref:svcproc:checking_squish_5_by_johnk.jpg?direct&300|}}|{{:techtalk:ref:svcproc:checking_squish_4_by_johnk.jpg?direct&300|}}| |
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| ====== Gaining a Squish Band Due to a Conversion ====== |
| **Converting an 883**: \\ |
An 883 head has a hemi chamber with no squish band but it's chamber is only 3" in diameter to match the 3" bore size of the 883. ((aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) \\ |
| What's fundamentally wrong with the hemi design is that it gives very poor chamber turbulence. \\ |
| Poor chamber turbulence means poor air/fuel mixing, resulting in pockets of fuel. \\ |
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| This is because you're now putting a 3-1/2" (1200) or 3-9/16" (1250) diameter piston under that hemi chamber. \\ |
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| 883 head on 883 cylinder (no squish). ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) | 883 head on 1200 or higher cylinder (squish gained) \\ Also 1200 head on 1250 or higher cylinder w flat top pistons ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) | |
| |{{:techtalk:ref:svcproc:squish_band_5_by_aswracing.jpg?direct&300|}}| {{:techtalk:ref:svcproc:squish_band_3_by_aswracing.jpg?direct&300|}}| |
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| **Converting a 1200**: \\ |
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| ====== Machined Squish Band ====== |
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| Check with your engine builder / supplier for further assistance if you're looking for a complete performance package. \\ |
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| Piston and head with matched squish band. ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) | |
| |{{:techtalk:ref:svcproc:squish_band_9_by_aswracing.jpg?direct&300|}}| |
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| ====== Reverse Dome ====== |
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| A piston with a reverse dome has a dish in the middle of it. \\ |
| That dish is needed because when doing a conversion, you've got a chamber that's sized for an 883 and a piston that's sized for a 1200 or 1250. \\ |
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| By dishing the middle of the piston deeply as shown below, the CR can be used on street bikes. \\ |
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| Reverse dome piston. ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) | 30° Reverse dome piston. ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) | Heads machined to match the pistons. ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/167919-883-to-1200-1250-conversion/page3?t=1802811&page=3)) | |
| |{{:techtalk:ref:svcproc:squish_band_6_by_aswracing.jpg?direct&300|}}| {{:techtalk:ref:svcproc:squish_band_7_by_aswracing.jpg?direct&300|}}|{{:techtalk:ref:svcproc:squish_band_8_by_aswracing.jpg?direct&300|}}| |
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| ====== Lightning Heads ====== |
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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 httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/89229-conversion-using-used-parts-where-to-go-from-here?t=715370)) \\ |
| These are what we call "Lightning" heads. \\ |
| 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. \\ |
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| ====== Thunderstorm Heads ====== |
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| 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. \\ |
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| 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. \\ |
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The angled squish bands direct the fuel being squeezed out of the squish bands more directly at the flame front. ((aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?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. \\ |
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| Anything higher than that and the dome goes past the squish band. \\ |
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| Stock Thunderstorm Heads ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?t=2206)) | Thunderstorms as Machined ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?t=2206)) | |
| |{{:techtalk:ref:svcproc:thunderstom_chamber_by_aswracing.jpg?direct&300|}}|{{:techtalk:ref:svcproc:thunderstorm_as_machined_by_aswracing.jpg?direct&300|}}| |
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| ====== Buell XB/04XL Heads ====== |
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As delivered, they have flat squish bands with a 62cc chamber. ((aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?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. \\ |
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| The Thunderstorms were a major step forward from the Lightning/Screaming Eagle heads, but the XB/04 XL1200 heads are even better. \\ |
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| Stock Buell XB Heads ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?t=2206)) | Machined XB Heads ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/1572-questions-about-buell-upgrade?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|}}| |
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| ====== Compression Ratio ====== |
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| Since the beginning of the Sportster line, Harley Davidson has changed head gaskets as way of changing or adjusting compression ratio. \\ |
| Some were lowered for gas mileage / EPA or raised for performance. \\ |
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| Then you can fine tune with gasket thickness. \\ |
| However; \\ |
<blockquote>Three tenths of a point in compression isn't really worth your time to tear it down. What's more, just the tolerance is greater than that. ((aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/123881-bumping-stock-compression-to-10-0-1?t=1230012)) \\ |
| In other words it's entirely possible your motor is already 10:1 or higher and likewise it's possible it's already 9.4:1 or lower. \\ |
| There's variation in every one of the dimensions and volumes that determines compression ratio. \\ |
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| ====== Effects of Deck Height ====== |
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| In general, deck height has nothing to do with the squish band. \\ |
| In the example below with a 3-9/16" bore and the chamber is about 3" in diameter. \\ |
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| (or use a thinner base gasket which accomplishes the same thing) \\ |
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{{:techtalk:ref:svcproc:stock_883_chamber_by_aswracing.jpg?direct&300|}} ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) {{:techtalk:ref:svcproc:bathtub_squish_by_aswracing.jpg?direct&400|}} ((drawing by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) \\ |
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| So there are situations where decking does change the squish clearance and situations where it doesn't. \\ |
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{{:techtalk:ref:svcproc:stock_thunderstorm_chamber_by_aswracing.jpg?direct&300|}} ((photo by aswracing of the XLFORUM httphttps://www.xlforum.net/forumsforum/showthread.phpsportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/160330-squish-band-clearance?t=1720575)) \\ |
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