Differences

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--- techtalk:evo:engmech03m [2021/08/10 00:53]
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hippysmack [Pics and Information on Evo Sportster Heads]
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 ====== Pics and Information on Evo Sportster Heads ======
+Article originally written by aswracing of the XLFORUM with further commentary by NRHS Sales of the XLFORUM and extended with further pics and information. ((http://xlforum.net/forums/showthread.php?p=4722973&highlight=883r+heads#post4722973)) \\
+Some of this information is now outdated as some of these heads have been obsoleted. \\
+However, the information itself is very informative regarding the changes and specs on the different stock heads. \\
+====== Evo Sportster Heads ======
+===== General Information =====
+There are 4 generations of Evo Sportster heads:
+  * 1986-1990 (4 speeds)
+  * 1991-2003 (5 speeds)
+  * 2004-present (rubber mounts)
+  * 2007-up (fuel injected)
+===== Casting Numbers =====
+|  1998 XL1200S Head Castings on Top ((photos by Hippysmack))  ||
+|{{:techtalk:evo:engmech:heads_-_1998_1200s_pic4_by_hippysmack.jpg?direct&300|}}|{{:techtalk:evo:engmech:heads_-_1998_1200s_pic3_by_hippysmack.jpg?direct&300|}}|
+===== Interchangeability =====
+Within a given generation, the heads are mechanically interchangeable between the different models, i.e. all bolt holes line up and no needed features are missing. \\
+Valve geometry is the same: 27° intake & 31° exhaust for a 58° included angle and the location of the valve tips is the same. \\
+The rocker box bolt pattern has not changed across any of these generations. A 1986 lower rocker box will bolt right up to a 2006 head and vice-versa. \\
+**Crankcase Breathing**: \\
+The only thing you need to be aware of is that the crankcase breathing arrangement has changed at each of the generations below. \\
+  * 4-speed models provided no facility in the head for a crankcase breather (the blind hole in each head is used to mount the carb).
+  * 5-speed models incorporated crankcase breathers into the carb mount bolts in the heads (open hole through head). \\ They also use a different middle rocker box that has a check valve incorporated (aka "umbrella" valve).
+  * Rubber mount models use an air/oil separator & check valve unit bolted into the lower rocker box. \\ (and do away with the middle rocker box, using a different top cover)
+**1991-2003 heads have been successfully fitted to 1986-1990 models**. \\
+The major difference you need to be aware of is that the spacing between the pushrod holes is different between a 4 speed and a 5 speed models. \\
+This is because the cam box geometry is different and the pushrods are at a different angle. \\
+So pay attention to the potential for pushrod rub where they pass through the heads into the rocker box. \\
+**2004-2006 heads have been successfully fitted to 1991-2003 models**. \\
+The new heads have the right front bolt hole relocated inboard 1/4", and also use 7/16" fasteners as opposed to the 3/8 fasteners used on the 1991-2003 models. \\
+You can either modify your existing front mount, or more recently a new mount has become available that solves this issue. \\
+Also, be aware that the 2004-2006 heads have larger fins and will overhang 1991-2003 cylinders somewhat, most noticeable on the left side. \\
+You can use your stock 1991-2003 rocker boxes or use the 04-up rocker boxes, either will work fine. \\
+**The 2007 and up fuel injected heads will technically fit older models but they are 1/8 wider in the intake manifold area**. \\
+So some folks report sealing issues when using on older bikes. \\
+They also have a different intake bolt pattern so you must use 2007 and up manifold flanges when using these heads. \\
+Anytime you're putting a different set of heads on your bike, you need to be aware of the chamber size & shape. \\
+And also how it relates to the piston you're using (to make sure they're mechanically compatible and will give the desired compression ratio). \\
+====== 883 XL Specific Information ======
+heads (ALL GENERATIONS) have a small, 49cc chamber that's approximately 3" in diameter to match the 3" bore of the 883. \\
+The chamber is also more shallow than the chamber in any other Sportster head. \\
+Valvetrain geometry is the same as the other heads except that small 1.580" intake & 1.350" exhaust valves are used. \\
+And the valves are longer to work with the more shallow and smaller diameter chamber. \\
+In stock configuration, these are the worst ports of any XL head, primarily due to the way the bowl area squeezes down to the small diameter valve. \\
+This arrangement causes a lot of turbulence. \\
+The heads respond well to a good porting and seat blending job, particularly when used with a larger valve that better matches the bowl size. \\
+The seats can accomodate the standard XLH1200 valve sizes (1.715 intake/1.480 exhaust) and special longer "conversion valves" are available to do this upgrade. \\
+You can have larger 1.760" Intake and 1.530" exhaust valves with stage 2 headwork (with the right machine shop and parts kit).
+When used in an 883 to 1200 conversion, reverse dome (dish) conversion pistons are available to give a workable compression ratio. \\
+Alternatively, the chamber can be relieved and the heads used with flat top pistons. \\
+These heads have an advantage over the XLH1200 hemi chamber head. \\
+The 3" diameter chamber provides a "squish band" around it's perimeter when placed over the larger 1200 bore. \\
+The squish band results in more turbulence and a more efficient chamber. \\
+However, the longer valves in these heads are also a disadvantage in that piston to valve contact issues are much more likely. \\
+Be concerned about this if the cams you're using have a high TDC lift figure on one or both valves. \\
+Most sets of 883 heads you come across will be silver in color. 883R and Iron models have black 883 heads. \\
+All are easily identified by the "883" script cast into them adjacent to the chamber. \\
+====== 1100 and 1200 XL Specific Information ======
+**1986-1987 XLH1100 HEADS**: \\
+These heads are very rare and very desirable. \\
+They came stock with large 1.840" Intake and 1.610" exhaust valves and a 62cc chamber which gave increased compression.
+**1988-2003 XLH1200 HEADS**: \\
+These heads have a 67cc hemispherical chamber, i.e. it's a round bowl with no squish band. \\
+Hemi chambers provide maximum valve unshrouding but also tend to have poorer chamber turbulence. \\
+The 67cc volume gives about 9:1 compression with flat tops at 1200cc. Domed pistons are readily available to raise this number up to 10:1 or higher. \\
+The pistons designed for this chamber have a radiused edge on the domes to fit well inside the hemi chamber shape. \\
+But the irregularity of the chamber (which is just a casting) makes it impossible to achieve a good squish band. \\
+Valve sizes are 1.715" intake and 1.480" exhaust. The stock seats can support only slightly larger sizes. \\
+(we fit them with 1.760" intakes and 1.530" exhausts when doing a Stage 2 job. For Stage 3 we change the seats) \\
+The ports on these heads are not particularly good, they have something of a squared off bowl and a low floor. \\
+In other words, these are areas where they need more material. These heads are all black with polished fins. \\
+**2004-up XL1200 Heads (all models)**: \\
+These are the best heads the factory has ever put on a Sportster. \\
+They are virtually identical to the Buell XB heads with 1.810" Intake and 1.575" exhaust valves with 7mm stems. \\
+They have 62cc bathtub shaped combustion chambers. They are either all black or black with highlighted fins. \\
+|  1998 XL1200S Heads  ((photo by Hippysmack))  |||
+|{{:techtalk:evo:engmech:heads_-_1998_1200s_pic1_by_hippysmack.jpg?direct&300|}}|{{:techtalk:evo:engmech:heads_-_1998_1200s_pic2_by_hippysmack.jpg?direct&300|}}|{{:techtalk:evo:engmech:heads_-_1998_1200s_pic5_by_hippysmack.jpg?direct&300|}}|
+====== Buell Heads ======
+===== General Information =====
+There are 2 generations of Buell heads:
+  * 1995-2002 (tube frame models, aka "tubers")
+  * 2003-present (XB models) (last edited in 2014)
+**1995-2002 Buell heads can be considered the same generation as 1991-2003 Sportster heads**. \\
+The rocker box and head breather arrangements are identical, as are the fin sizes. \\
+The front mount holes have the same spacing as the 1991-2003 Sportster heads but use 7/16" NC fasteners. \\
+(exception: 1995-1996 S2 models use a 3/8" fastener on one side and a 7/16" fastener on the other). \\
+**2003-present Buell heads can be considered the same generation as 2004-present Sportster heads**. \\
+(in that they use large fins and 7/16" front mount fasteners with the right front mount hole moved inboard 1/4"). \\
+The main difference is that the XB head does not provide head breather/carb mount bolt holes. \\
+The bosses are cast in, however, and the holes can be drilled and tapped. \\
+Buell XB models don't need these bolt holes due to the downdraft fuel injection system they come with. \\
+Crankcase breathing is provided on stock XB models through the tops of the rocker box covers. \\
+====== Buell Specific Information ======
+**1995-1996 BUELL S2 HEADS**: \\
+These heads are identical to the 1988-2003 XLH1200 heads in all respects except that one of the front mount bolt holes is 7/16" NC instead of 3/8" NC. \\
+So don't be fooled; not all "Buell Heads" are higher performance than Sportster heads. \\
+**
+-2003 LIGHTNING HEADS**: \\
+This is a head that came out in 1996 on the Buell S1 Lightning model, as well as the 1200S Sportster Sport model. \\
+The 1200S version is black with polished fins and has dual plugs, the second plug being accessible through the hole in the top of the rocker box. \\
+The Buell S1 version is silver and has a single spark plug. Versions of this head were also sold in the Screaming Eagle catalog. \\
+Early versions were silver and carried the "Lightning" script above the pushrod area. A version was sold in black polished with no script. \\
+And finally, a black polished version was sold with the "Screamin Eagle" script and dual plugs. Also, the Buell Blast comes with a version of this head. \\
+The valve sizes are 1.715" intake and 1.480" exhaust (identical to the 1988-2003 XLH1200 head. \\
+The same seats are used so Stage 2 Lightning heads get 1.760" intakes and 1.530" exhausts. \\
+The ports are also identical to the 1988-2003 XLH1200 head. \\
+Later SE versions were advertised as having 8% higher flow than stock XLH1200 heads. \\
+But as someone who's flow tested lots of them, I just haven't seen it. The range of numbers I get has been the same. \\
+The only place this head is different from the 1988-2003 XL head is in the chamber. \\
+Extra material was added, as well as a 10° squish shelf, bringing the volume down to about 62cc. \\
+This gives around 10:1 when paired with flat top pistons. The squish band though does nothing with a flat top. \\
+So the performance increase from this head comes entirely from an extra point in compression ratio. \\
+This extra material in the chamber somewhat shrouds the valves, however, hurting low lift flow. \\
+It gets especially bad when oversize valves are fitted. \\
+When putting larger valves into Lightning heads, we always unshroud the chamber around the valve heavily to improve flow. \\
+This of course raises the chamber volume and requires us to deck the head significantly to get the volume back to 62cc. \\
+Often we'll end up re-cutting the squish band to 15° and just size the chamber out to 67cc instead, and then put the customer into a Thunderstorm type domed piston. \\
+We did, however, offer a 10° piston designed for the stock Lightning head that offers 10.5:1 compression at 62cc. \\
+**1998-2002 BUELL THUNDERSTORM HEADS**: \\
+This was the second generation high performance head to come out on Buells. \\
+It was introduced in 1998 on the S1W and S3/S3T (the S1 and the M2 retained the Lightning heads in 1998). \\
+In 1999, all models came with Thunderstorms and it remained that way through the 2002 model year. \\
+This head went back to the 67cc volume and instead used a domed piston to raise the compression ratio. The advantage to this is that it heavily unshrouded the valves. \\
+A 15° squish shelf was incorporated into the chamber and matched to a 15° dome angle on the piston. \\
+Also, valve sizes were increased to 1.810" intake and 1.575" exhaust. Ports were improved as well, particularly in the bowl. \\
+The squish shelf on a Thunderstorm head is still a casting, however, and as such it's not very accurate. \\
+There's a good sized overhang between the deck and the perimeter of the squish shelf, and core shift often makes the squish shelf uneven from side to side. \\
+So while it's nice to have a squish shelf and the turbulence it generates, it's effectiveness is limited unless you re-machine it. \\
+(which generally requires .030"-.040" to be removed from the deck) \\
+Still, this head performs substantially better than the Lightning or XLH1200 head. \\
+All Thunderstorm heads are black powder coated, without highlighted fins. \\
+**2003-up BUELL XB heads**: \\
+These heads are virtually identical to the 2004-up XL1200 heads but they do not have provisions for breathers as noted above. \\
+You can drill and tap for breathers though if needed. They come in either silver or all black color depending on model and year. \\

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