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techtalk:ref:engmech05 [2019/08/22 13:08]
hippysmack [Pics of Aftermarket Breather Valves]
techtalk:ref:engmech05 [2019/10/12 03:56] (current)
hippysmack
Line 112: Line 112:
 To stop a leak, you may be tempted to tighten the bolts even more. \\ To stop a leak, you may be tempted to tighten the bolts even more. \\
 This could result in breaking the bolt. \\ This could result in breaking the bolt. \\
 +
 +On 04-up heads, changing to aftermarket breather bolts means using bolts with the bigger I.D. (91-03) style bolts. \\
 +The results of using the bigger holed bolt would be a slower rate of outflow and less positive crankcase pressure on a stock motor. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2073932&​page=4)) \\
 +But the timing of the upstroke is the same which then pulls a vacuum. \\
 +The umbrella valve will close down only when inside air pressure is lower than outside air pressure. \\
 +If the inside pressure can't get out fast enough before piston upstroke happens the umbrella may '​float'​ or not close all the way. \\
 +If the umbrella floats, X amount of extra air is pulled in until it does close. \\
 +(on top of what didn't get completely out on the last downstroke = more air in the engine on the next downstoke = oil puking out the breather). \\
 +How much slower the bigger bolt hole yields will vary with different engines. \\
 +
 +However, the smaller holed bolts were designed to OEM specs internally. \\
 +If you've upgraded to bigger pistons, there will be more positive pressure displaced out the breathers on downstroke. \\
 +This may negate the need for higher pressure generated by the smaller holed bolts. \\
 +This may be something you'd want to watch since there isn't sufficient data to prove one way or the other. \\
  
 {{:​techtalk:​ref:​engmech:​breather_mod_2_by_hagen.jpg?​direct&​300|}} ((photo by Hagen of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=146084&​page=11)) {{:​techtalk:​ref:​engmech:​ds_breather_bolt_by_hagen.png?​direct&​300|}} ((photo by Hagen of theXLFORIM http://​xlforum.net/​forums/​showthread.php?​t=692845)) {{:​techtalk:​ref:​engmech:​broken_banjo_bolt_by_scout99.jpg?​direct&​200|}} ((photo by Scout99 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=28299)) {{:​techtalk:​ref:​engmech:​breather_mod_2_by_hagen.jpg?​direct&​300|}} ((photo by Hagen of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=146084&​page=11)) {{:​techtalk:​ref:​engmech:​ds_breather_bolt_by_hagen.png?​direct&​300|}} ((photo by Hagen of theXLFORIM http://​xlforum.net/​forums/​showthread.php?​t=692845)) {{:​techtalk:​ref:​engmech:​broken_banjo_bolt_by_scout99.jpg?​direct&​200|}} ((photo by Scout99 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=28299))