Crankcase Breathers |
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Crankcase Breathers |
McMark |
Sep 12 2017, 04:58 PM
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#41
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
I was looking at the factory manuals and talking with someone about crankcase breathers. We were talking about breather setups for carbs specifically. And I realized as I was looking at the breather diagram that it appears that the breather ports on the heads were included to supply extra air to flow through the engine case. And then I read this little snipped in the manuals which seems to support my thought:
QUOTE Crankcase ventilation has been considerably improved in the engine by ducting fresh air from the air filter. This modification reduces crankcase condensation and icing at low outside temperatures. So following that logic... If the crankcase breather (at the oil filler neck) isn't connected to a vacuum source, then the ports at the heads should/could be plugged instead of connected to a breather box. Thoughts? Contradictions? Agreement? I realize people have been connecting breathers all sorts of different ways and most work just fine. I'm more interested in the theory aspect, and refining an 'ideal' installation since we already know many ways to 'make it work'. Attached image(s) |
McMark |
Oct 27 2017, 12:13 PM
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#42
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Just found this in the 1975 Emissions book that came in the glovebox with the operation manual. Oddly it shows the filler neck vent connecting to the air cleaner, and the head vents connecting to what appears to be the plenum, which is completely backwards to how we know the system is hooked up. But it does show that the air flow is intended to flow into the heads and out of the filler neck.
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worn |
Oct 27 2017, 01:33 PM
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#43
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can't remember Group: Members Posts: 3,164 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
Just found this in the 1975 Emissions book that came in the glovebox with the operation manual. Oddly it shows the filler neck vent connecting to the air cleaner, and the head vents connecting to what appears to be the plenum, which is completely backwards to how we know the system is hooked up. But it does show that the air flow is intended to flow into the heads and out of the filler neck. I like how they show air going two opposite directions in the same line. Might it be that they expect the air to oscillate and eventually particulate matter would be sucked into the intake? I also am wondering about the term flash arrestor used for the T that connects the two rubber lines from the heads. Is that so a backfire cannot ignite the case vapors? |
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