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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]
hippysmack
@@ Line 112: / Line 112: @@
 To stop a leak, you may be tempted to tighten the bolts even more. \\
 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))

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