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techtalk:ref:engmech04k [2020/10/06 15:29] hippysmack [Breather Valves (1957-Up)] |
techtalk:ref:engmech04k [2020/10/09 13:54] hippysmack [Breather Valves (1957-Up)] |
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| **The 1972-1976** breather valve opens 20°-25° (ATDC) and closes 85°-90° (ABDC), less duration than the 57-71 breather. \\ | **The 1972-1976** breather valve opens 20°-25° (ATDC) and closes 85°-90° (ABDC), less duration than the 57-71 breather. \\ | ||
| + | |Left is the unmodified 1/4 speed R \\ valve. Right is the 1000 stock.|R model is the left one.| | ||
| + | |{{:techtalk:ih:engmech:cc_flow_4_by_dr_dick.jpg?direct&200|}}|{{:techtalk:ih:engmech:cc_flow_5_by_dr_dick.jpg?direct&300|}}| | ||
| **1977-78 models only**: ((Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=518948&highlight=cam+chest+breather)) \\ | **1977-78 models only**: ((Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=518948&highlight=cam+chest+breather)) \\ | ||
| The timed breather on the oil pump drive was dropped. \\ | The timed breather on the oil pump drive was dropped. \\ | ||
| - | Without the breather gear that means you less control of the oil / air density in the crankcase. \\ | + | Without the breather gear that means you have less control of the oil / air density in the crankcase. \\ |
| An external non-return valve was plumbed into the breather vent tube sticking down from the timing cover at the generator drive. \\ | An external non-return valve was plumbed into the breather vent tube sticking down from the timing cover at the generator drive. \\ | ||
| This allows air out, but not in. It is sometimes referred to as the foo-foo valve. \\ | This allows air out, but not in. It is sometimes referred to as the foo-foo valve. \\ | ||
| Line 126: | Line 128: | ||
| - | 57-76 engines breath and scavenge oil from the same oil galley in the rear of the sump. \\ | ||
| - | <blockquote>The shallow sump, timed breather system, comes from the aviation world of old. ((mrmom9r of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=4)) \\ | ||
| - | Piston driven aircraft had to be able to evacuate the oil from the crankcase regardless of engine altitude and that system does that. \\ | ||
| - | At the time Harley adapted that system they were copying the highest engine technology of the day. \\ | ||
| - | They just took too long to abandon it as technology advanced. \\ | ||
| - | Documents from HD Racing from the period show no HP gain between the 2 ironhead systems when the breather is properly timed ( which didn't happen a lot). \\ | ||
| - | </blockquote> | ||
| - | The rotary breather valve is integrated with the oil pump. The gear on top of the valve also operates the oil pump. \\ | ||
| - | The breather valve connects the flywheel area to the gearcase. \\ | ||
| - | |||
| - | The rotary breather valve functions to relieve pressure in the crankcase caused by the downstroke of the pistons and it controls the flow of oil in the lubrication system. \\ | ||
| - | It is timed to engine rotation and opens on the downstroke of the pistons. ((1960 HD FSM pg 3a-15)) \\ | ||
| - | This allows crankcase exhaust air pressure to expel the scavenge oil from the crankcase breather oil trap into the gearcase. \\ | ||
| - | The breather valve then closes on piston upstroke, creating vacuum in the crankcase. \\ | ||
| - | Crankcase exhaust air from the gearcase is sent out the breather tube. \\ | ||
| - | Any oil still in suspension with the air on the way to the breather tube is separated by an oil slinger on the generator drive gear. \\ | ||
| - | |||
| - | |Left is the unmodified 1/4 speed R \\ valve. Right is the 1000 stock.|R model is the left one.| | ||
| - | |{{:techtalk:ih:engmech:cc_flow_4_by_dr_dick.jpg?direct&200|}}|{{:techtalk:ih:engmech:cc_flow_5_by_dr_dick.jpg?direct&300|}}| | ||
