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) |
Beebo Kanelle |
Sep 12 2017, 05:55 PM
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#42
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Member Group: Members Posts: 248 Joined: 22-November 12 From: Houston, Texas Member No.: 15,177 Region Association: Southwest Region |
I always want the crankcase ventilation to be just that. Venting the crankcase. I'm afraid that the venting of the heads inhibits oil drainage back into the crankcase and may, in fact, exacerbate oil loss.
Just my 2 cents... |
McMark |
Sep 12 2017, 07:05 PM
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#43
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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 always want the crankcase ventilation to be just that. Venting the crankcase. I'm afraid that the venting of the heads inhibits oil drainage back into the crankcase and may, in fact, exacerbate oil loss. Just my 2 cents... It could inhibit drainage if there is no vacuum source on the breather, since that configuration would make all ports into exit ports. But on a plenum based engine with the case ported to manifold vacuum, are would almost always be sucked in the heads and flow down the pushrods tubes to the case, which would aid drainage. To really compare anecdotes we need some pertinent info: 1. Heads ported? Where to? 2. Case ported to vacuum? (Air filters are not vacuum, ever) 3. Functional PCV valve? 4. Stock-ish or Wild engine? |
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