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) |
Mark Henry |
Oct 27 2017, 10:18 PM
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#42
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Stock FI engine I'd just put it back stock, head vents I block if I can, but I do whatever is easier.
Performance I've hooked them up with head vents and without and never noticed any difference. Most times I prefer no head/rocker vents. I've always vented to the carbs (or ITB) through the air cleaner with no ill effects. An added plus is no fine oil mist covering the whole engine. On the bugs and even my bug with the big T4 my breather is just a box, top hose goes to the carb air cleaner, bottom hose drains back in the case, vents are in the middle. Never seen a problem with draining back to sump or venting to the carbs. The /6 guys don't like to drain back to the sump, the only reason my /6 puke can has a drain valve to empty the can. |
98101 |
Dec 28 2017, 03:46 PM
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#43
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Michael in Seattle Group: Members Posts: 373 Joined: 7-October 17 From: Seattle, WA Member No.: 21,495 Region Association: Pacific Northwest |
I've always vented to the carbs (or ITB) through the air cleaner with no ill effects. An added plus is no fine oil mist covering the whole engine. On the bugs and even my bug with the big T4 my breather is just a box, top hose goes to the carb air cleaner, bottom hose drains back in the case, vents are in the middle. Never seen a problem with draining back to sump or venting to the carbs. I'm thinking about doing this with my carbed 2366. Any downsides to this approach? |
Mark Henry |
Dec 29 2017, 08:36 AM
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#44
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
I've always vented to the carbs (or ITB) through the air cleaner with no ill effects. An added plus is no fine oil mist covering the whole engine. On the bugs and even my bug with the big T4 my breather is just a box, top hose goes to the carb air cleaner, bottom hose drains back in the case, vents are in the middle. Never seen a problem with draining back to sump or venting to the carbs. I'm thinking about doing this with my carbed 2366. Any downsides to this approach? Mark...but aren't you sending that fine oil mist into the carbs? That can't be good? Mike Building engines since 1990, not once have I seen a downside. OEM systems have been doing the exact same thing for ages. Over the years I done many top end jobs on engines I've built, T1 & 4 performance engines I always dump the vent into cylinder #3, straight down into the throat. Not once have I seen any difference in the intakes or combustion chambers, no unusual coking, no excess oil, no wear difference...nada. It's a very fine, highly atomized mist and a small amout, it's not like you're burning the oil for fuel. If you do feel it's causing an problem it's much more likely to be another issue such as worn valve guides. |
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