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techtalk:ref:engmech01m [2018/10/29 17:29]
hippysmack [For Cutting the Cover] 		techtalk:ref:engmech01m [2024/01/14 18:21] (current)
hippysmack
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 ====== REF: Engine Mechanicals - Sub-01M ====== ====== REF: Engine Mechanicals - Sub-01M ======
-====== ​Chopping the Cam / Gearcase Cover ====== +====== ​Notes on Sifton Cams by Tom Sifton ​======
-See also: \\+
  
-  * [[techtalk:​ref:​engmech01n#​pics_of_cam_gearcase_cover_mods|Pics of Cam / Gearcase Cover Mods]] +Instructions for Installing Special XL Cams {{:techtalk:​ref:​engmech:​siftoncams-tomsifton-inst-1.jpg?​200|}}{{:techtalk:​ref:​engmech:​siftoncams-tomsifton-inst-2.jpg?​200|}} 
-  * [[techtalk:​ref:​engmech01o#​pics_of_sprocket_cover_mods|Pics of Sprocket Cover Mods]] +(Posted by Staffords on the [[https://​www.xlforum.net/​forum/​sportster-motorcycle-forum/​sportster-motorcycle-era-specific-and-model-specific/​ironhead-sportster-motorcycle-talk-1957-1985/​205448-tom-sifton-special-xl-cam-instructions?​t=2082886|XLForum]])
-  ​* ​[[techtalk:ref:​engmech01l#​ignition_cover_mods_and_aftermarket_covers|Ignition Cover Mods and Aftermarket Covers]]+
  
-====== Some Suggestions and Tools ====== +1. Check cam length clearance for end play in cam case, allowing at least .005.
-**Benefits of chopping the cover**: \\ +
-There no benefits whatsoever of chopping the cover other than to change the cosmetic appearance of it. ((Moved On http://​xlforum.net/​forums/​showthread.php?​t=22500V)) \\ +
-All you're doing by chopping / machining it is changing the look. \\+
  
-**Design**: \\ +2. Check each cam shaft end in the bearing that it fits to be sure it is free.
-You can sketch out a design and lay it up on the bike as it would be installed. \\ +
-That way, you get to see it before cutting it which may cut down on costs of another one after the fact.  +
-|{{:​techtalk:​ref:​engmech:​sprocket_cover_sketch_by_blacktooth_grin.jpg?​direct&​400|}} ((Sprocket cover sketch by Blacktooth Grin of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=6))|+
  
 +3. On 1957 and 1958 motors, grind upper end of tappetts at 45 degree angle 1/16" and also grind lower edge of the lower pushrod gasket hole at 45 degrees, in order to provide clearance when the tappett is at the top of the cam. If this is not done, it will cause the tappett to contact the gasket and will act as a pump, forcing oil to leak around the gasket. The lightweight KR tappetts that you should use are slightly longer than the XL tappett, and the tappett also lifts higher due to the cam action, thus causing this condition. THIS IS NOT NECESSARY ON 1959 AND LATER MOTORS.
  
-**Oil Passages**: \\ +4. (updated) For XL STROKER INTAKE AND EXHAUST CAMS - Both inlet and exhaust cam lobes move the valve .436. See that there is 1/2" clearance between the uppoer end of the valve guide and the underside of the valve spring collar when the valve is on the seat. Check this with both valve springs and with the collar and keepers assembled. If there is less than 1/2", then grind off the upper end of the valve guide. Then assemble with inner spring only in place, shim or grind so that spring will become boilbound (fully compressed) at .450 to .455 of the valve travel. Then remove inner spring and install outer spring. Shim or grind so that spring is coilbound at .465 to .470 of valve travel.
-Check the oil passages around ​the bushings before you start cutting ​on the cover. \\ +
-Some have a factory drilled oil passage (1/8") through ​the cover going to the pinion bushing area. The hole on the lower edge of the cam cover was then welded to seal this hole. ((ericfreeman http://​xlforum.net/​forums/​showthread.php?​t=467551&​page=2)) \\ +
  
-After cutting thru this hole, it can be plugged again by running ​a 1/​4"​x20 tap in and threading ​a screw into it with JB weld / epoxy applied. ((Johnny Wolf of the XLFORUM http://​xlforum.net/forums/​showthread.php?​t=525868)) +From the above, you can see tha in the event of over revving that we want the valve float to be checked ​by the inner valve spring which would be a sfter action than if the valve collar were to strike the end of the valve guide. We want the outer spring to have a little more clearance because, as you know, these springs do not become coilbound all the way around; they strike first on the one side where the end coils are ground off flat. This off side pressure would cause undue bending strain on the valve stem if it (the outer spring) was the point of contact that stops the valve travel in event of float due to over revving. After the valve travel has been checked, we want at least another 1/16" of clearance between the underside of the collar and the upper end of the guide.
-|{{:​techtalk:​ref:​engmech:​cam_cover_mod_9_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_10_by_johnny_wolf.jpg?​direct&​300|}}|+
  
-**Dowel Pins**: \\ +5. Adjust ​the tappett clearance to from just free to .002. This adjustment IS TO BE MADE WITH THE PISTON ON TOP DEAD CENTER OF THE POWER STROKE in order to be sure that you are not adjusting when the tappett is on the cam ramp.
-It's also important to keep the dowel pin holes intact. With dowels front and rear, \\ +
-It ensures ​the accurate alignment of the bearings / bushings in use. ((Folkie of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=20)) \\  +
-It also ensures correct alignment of the cam cover if or when you have to line ream replacement cam bushings. ((steelworker of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=19))+
  
-**Cutting the cover while installed**:​ \\ +6. You may have to enlarge ​the gas line fittings and replace ​the tank gas petcock in order to supply sufficient gasoline for high speed operation. If this is not done, you will surely ​be troubled with gas starvation at high speed.
-While it is possible ​to cut the cover down while it is installed on the engine, it's safer to remove it. \\ +
-When removed, the cutting can be done more easily and the finish more smoothly. \\+
  
-When installed, the issue is more avoiding the oil lines and oil pump,  \\  +7. Standard spark lead is O.K., and you may gain some by advancing ​to 48 degrees.
-Especially the return line that already gets worn thin by rubbing the back side of the cover. \\  +
-It would also be very difficult ​to see what you are doing there on the top back side (near the pulley). ((JackalAR of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=21))+
  
-Get everything out of the way. \\ +Best performance should ​be at 6300 to 6400 RPM.
-Tape off the area to be cut. \\ +
-Use a muffler cutter air tool (or other) ​to remove most of the material. \\ +
-Then work it with a file to the desired shape. +
-Always take off less than more. You can keep cutting, but if you go to far you can't put it back. \\ +
-It's time consuming and harder to do than having the cover off. ((in the wind of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=22)) \\+
  
 +Motor should not be revved over 7000 RPM at any time.
  
-**To remove ​the cam cover**: \\ +For all out best results, you should use straight pipes measuring 37" from the edge of the cylinder ​to the long end of the beveled cut. The new XLCH exhaust pipes are satisfactory. 40" ​will accelerate better, but 37 to 38 is best at top RPM.
-The lower rocker box has to come off the head (properly) enough ​to relieve tension on the pushrods / valves / lifters / cams. ((JackalAR ​of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=21)) \\ +
-Without the spring tension, the cams will want to follow the cover, so keep on eye on them and go slowly. \\  +
-You might have to stick something between the case and cover, and push them back in as the cover comes off ((Joe Dirt of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=4)) (like a screwdriver or putty knife).+
  
-Guys do it either way (cover on / cover off), so it's whatever you decide to do ((Joe Dirt http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=6)) (with an educated decision). ​ \\ +TOM SIFTON
-But, with the cam only being supported by the bushing on the one end and the valve spring pressure pushing down, \\ +
-There is chance of damage to any cam bushing (cover or case) while removing or installing the cover. \\+
  
-With valve spring tension on the cam lobes, once the cover is removed, the tension pushes down (vertically) on the cams. \\ +\\ 
-With a very tight cam to bushing tolerance, there is little room for vertical movement. ​\\ +\\
-The tension can shove the end of the steel camshaft into the soft bushing bore and damage it. \\  +
-(as tension pushes one end down, the other end moves up and can gouge the bushing)+
  
 +The following text was scribbled over (after Item# 7):
  
-Just be careful sliding the cover off. Make sure you come straight out slowly, and look inside ​the case with a flashlight. \\ +I suggest that you use the XLCH high compression piston rather than shorten the cylinders to obtain high compression, because ​you will have some trouble clearing ​the valve, especially ​if you use, and you should use, the large XLCH inlet valves. If you do shorten ​the cylinders, then you should check the valve head clearance ​by placing molding wax on the valve heads, then assembling ​the engine and adjusting ​the pushrod clearance ​and turn the engine ​over slowy by hand (cams, of course, being in time) to obtain impressions that you can measure to see that you have sufficient clearance. The XLCH piston ​will clear and will be more efficient because ​the valve clearance is obtained by lowering ​the piston rings which allows slabbing off the piston which does away with the airflow interference that is present ​with cupped out pockets in the piston heads.
-When you get it cracked open, make sure you're not pulling ​the cams out. ((64physhy of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=9)) +
- +
- +
-===== For Cutting the Cover ===== +
- +
-    * Saws-all. +
-    * Angle grinder with a metal cutting blade. +
-    * Hacksaw. +
-    * Jigsaw. +
-    * A Dremil rotary tool can be used but the metal cutting blade is too small to cut at 90° angles. \\ The O.D. of the body is wider than the cutting bit. \\ (You'​ll end up making angled cuts instead of straight ones (good if that is intended). \\  +
-    * A mechanical or CNC mill is very helpful for precise ​and non-jagged cuts. +
- +
-  * **Caution**:​ Be in control of any power cutting tools at all times. Kick-back can do serious bodily harm. \\ If the cover jumps out the clamped area, let it fall. Make sure the cutting blade has stopped and the tool properly secured before worrying about the cover. +
- +
-|Cutting area marked out with tape. \\ Cuts made with an angle grinder with the metal cut-off blade. ((photos by Johnny Wolf of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=467551))|| +
-|{{:​techtalk:​ref:​engmech:​cam_cover_mod_1_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_2_by_johnny_wolf.jpg?​direct&​300|}}| +
- +
-|Cover mounted to 2x4 table end with large "​C"​ clamps and cut with a saws-all. ((photos by EvIL sTevE of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1395634&​page=2))||| +
-|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_1_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_2_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_2.1_by_evil_steve.jpg?​direct&​300|}}| +
- +
-|Cover bolted to a sheet of steel as a jig to hold the cover in a vise for machining the excess off with a milling machine ((photos ​by hoosier xlc of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1104997))||| +
-|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_mill_1_by_hoosier_xlc.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_mill_2_by_hoosier_xlc.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_mill_3_by_hoosier_xlc.jpg?​direct&​300|}}| +
- +
-===== To Protect ​the Aluminum from Scratches While Cutting ===== +
- +
-    * Painters tape. +
-    * Soft jaws in a bench vise. +
-    * A towel to wrap the cover in before chucking into a bench vise. +
-    * Plywood between ​the cover and the vise or clamp jaws. +
- +
-|Place the tape over all areas where the cutting tool might \\ butt into the cover. The towel protects the cover from \\ being gouged ​by the vise jaws. ((photo by Johnny Wolf of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=467551))| +
-|{{:​techtalk:​ref:​engmech:​cam_cover_mod_1_by_johnny_wolf.jpg?​direct&​300|}}| +
- +
-===== For Holding the Cover While Cutting ===== +
- +
-  * The bench vice above will work well for cutting the cover with a handsaw. +
-  * The wooden table below while clamping the cover to it with large "​C"​ clamps ​will hold the cover tighter in place. +
-  * However when using an angle grinder or most power saws, if the blade catches ​the wrong way while cutting, it will jerk the piece out of the work station. +
- +
- +
-|Cover mounted to 2x4 table end with large "​C"​ clamps and cut with a saws-all. ((photos by EvIL sTevE of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1395634&​page=2))||| +
-|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_1_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_2_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_2.1_by_evil_steve.jpg?​direct&​300|}}| +
-===== For Shaping and Smoothing ===== +
- +
-    * Angle grinder. +
-    * Bench grinder. +
-    * Belt sander. +
-    * Palm sander +
-    * Hand files. +
- +
-Try a belt sander first and then finish with a palm sander. ((1200C of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=22500&​page=7)) \\ +
-You can use a heavy sander up to '​almost'​ the line to stop. Then light finish to the line. \\ +
-This is where a large part of the project is spent. \\ +
- +
-|Basic shaping done with the sander and files. (this can take several hours) ((photos by Johnny Wolf of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=467551))||| +
-|{{:​techtalk:​ref:​engmech:​cam_cover_mod_3_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_4_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_5_by_johnny_wolf.jpg?​direct&​300|}}| +
- +
-|This cover was shaped with a combination of grinding stones, flapper wheels, an angle grinder with a sandpaper disc and palm sanders. ​ ((photos by EvIL sTevE of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1395634&​page=2))||| +
-|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_3_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_4_by_evil_steve.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​chopping_cam_cover_with_a_saws-all_5_by_evil_steve.jpg?​direct&​300|}}| +
- +
-===== For Finishing ===== +
- +
-    * Wet dry 220/400. +
-    * Steel wool. +
-    * WD-40. +
-    * Aluminum polish. +
- +
- +
- +
- +
-|The mounting holes were notched near the cut areas to make them all symmetric. \\ The surface was finished with steel wool/WD-40 and aluminum polish ((photos by Johnny Wolf of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=467551))||| +
-|{{:​techtalk:​ref:​engmech:​cam_cover_mod_6_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_7_by_johnny_wolf.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​cam_cover_mod_8_by_johnny_wolf.jpg?​direct&​300|}}|+
  
 +Obtaining the desirable compression ratio with the XLCH piston also saves you a lot of trouble in fitting the inlet manifold that is necessary when you shorten the cylinders, bringing the inlet ports closer together.
  
 +If you assemble as I have suggested, a stripped down Sportster with a 150 lb. rider that can get down out of the wind, with magneto ignition and generator removed, should pull 3.70 gear, and should run better than 130 MPH, and should do better than 105 MPH in the 1/4 mile with 4.70 to 4.80 gear.
  
 +The following was the original text of Item #4: (scribbled over)
  
 +The cam causes the valve to travel .375 plus .017 ramp total lift at valve .392; therefore, the inner valve spring should become coilbound at .407 with the outer spring becoming coilbound slightly later (about .422). There must be at least 15/32" clearance between the underside of the valve spring collar and the upper end of the valve guide.
  
  

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