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| Crankcase ventilation setup | Rate Topic |
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| Posted: 12-09-2023 01:35 am |
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1st Post |
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JH12947 Member
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Hi all - I'm looking for some information/confirmation of the crankcase ventilation and oil capture setup that would have been on the car from stock. My car is a 1973, vin 12947 with engine 3077. I gather that all cars have a port in the crankcase, some cars also had a drain tube that drained oil from a separator back into the sump, and later cars also had a tube running from the rocker cover to the airbox. My car only has the crankcase outlet - nothing else remained on the car when I got it. Picture attached is the crankcase port into which I have put a breather while I get it running. I am planning on running a tube from the crankcase to an oil catch can and either venting it or running a tune to an airbox when I eventually get one. Any thoughts on what is best here - should I install a rocker cover line as well? And also, I'm curious as to the reason there is a spring shown in the system diagram where the tube enters the crankcase. Cheers, Corey Attachment: IMG_1994.jpg (Downloaded 68 times)
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| Posted: 12-09-2023 10:30 pm |
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2nd Post |
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JH12947 Member
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After a bit more research it appears that I may have a bit of a hodgepodge of components and perhaps a non-original engine. The car does have a bracket on the firewall for the oil separator (though I don't have it), but the engine does not have a sump with the provision for the oil to drain back in. The valve cover has a oil fill cap, but no vent tube. Another post states that the oil separator was only installed up to engine #2759, so 3077 may not require it. There is also a post that says that MkII engines had a built-in oil separator - not sure where that would be. Leaves me with a hole in the top of the crankcase from which I can collect oil but no way to return it to the sump. It may be best just to collect it in a catch can and keep an eye on the oil level but I'm open to input on it. EDIT - Just checked the Marten Robey site and it looks like the oil return was just and extra fitting on the sump drain plug. I may look to replicate this and add a drain unless I can confirm that the whole thing is unnecessary on this engine. Last edited on 12-09-2023 10:36 pm by JH12947 |
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| Posted: 12-11-2023 01:22 am |
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3rd Post |
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Art DeKneef Member
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On my 74 MK 2 engines that breather is a hose that goes from that hole to the back of the air box. Any excess by-product would go into the airbox and get sucked into the carb and get burned up. Art
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| Posted: 12-11-2023 02:55 am |
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4th Post |
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JH12947 Member
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Thanks Art - I think that is what I will eventually end up doing. I had another look at my oilpan and the drainplug is on the left side directly under the exhaust so running a drain tube will not work. I have dellortos without an air box so will either have to do that after I get a box, or just collect the oil in a can and drain as needed.
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| Posted: 12-11-2023 10:11 pm |
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5th Post |
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Jh092 Member
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I have dellortos and ended up adding a small catch tank next to windshield washer reservoir. Don Attachment: Compress_20231211_164746_6222.jpeg (Downloaded 46 times)
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| Posted: 12-11-2023 10:21 pm |
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6th Post |
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JH12947 Member
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Thanks - Is the breather below your rear dellorto coming directly from the crankcase vent hole?
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| Posted: 12-11-2023 10:39 pm |
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7th Post |
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Jh092 Member
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Yes it is. Plan for over the winter is to feed it into the catch tank.
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| Posted: 12-13-2023 05:17 pm |
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8th Post |
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redracer Member
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Corey: As Art stated, the later engines had the breather tube go from the rear crankcase breather(like yours) to the airbox. The earlier '73 engines had a catch-can separator mounted to the firewall with the breather hose going down to a "Y" pipe where the oil was drained. When I autocrossed one of my cars, I was allowed to have a catch can, so I built(welded) a rectangular box with an internal angled metal plate and mounted it behind the engine dampener(near the brake booster). What would happen if your oil was at the full level, on a hard left turn oil would get dumped into the airbox and look like you had "blown" your engine as the smoke billowed out the exhaust pipe, but in reality, your were fine. Before adding the catch can, we would keep the oil level about 1/2 quart below the fill line to avoid this embarrassment! On the race cars, the ideal place for the breather is the square section on the auxiliary oil pump housing as it is high up and free from oil sloshing into it. Call/SKYPE/email me if you want more info, bruce/RedRacer
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