Oil breather pipe; rocker cover to air filter

Groundes-Peace · Jan 2nd, 2018, 20:08

Please explain what is the benefit/purpose of this arrangement versus having a filtered cap on the rocker cover....?

Derek UK · Jan 2nd, 2018, 20:19

With the later routing of the ventilation hoses the pipe from the air filter feeds clean air into the engine. The cap doesn't do anything with this routing and is just an oil filler cap. i.e. the direction of the air is from the filter into the engine.

Ron Kwas · Jan 2nd, 2018, 20:27

GP;

It's a variation on PCV system. Both provide fresh filtered air for PCV system, but when sourced from Air Filter, even during high crankcase pressure situation (high RPM, high blow-by) when crankcase pressure exceeds the rate of extraction by flow-limited path to intake manifold, crankcase gases would not be allowed to escape to atmosphere (and allow oil droplets to make a mess of the Valve Cover), but would be routed into Air-Filter where they would be sucked into carb intake (and when excessive, foul the Air-Filter, choking off front carb air).

See also: http://www.sw-em.com/pcv_diagrams_and_notes.htm

Cheers

Groundes-Peace · Jan 3rd, 2018, 12:42

Ron,
Thanks for the attachment which I had not seen before.
In my case when I had my engine rebuilt, I just had the basic filtered cap on the valve cover. However when I used the car on fast runs there was quite a quantity of oil misting on the valve cover. I then went for the hose return route into the front air filter, which overcame the messy build up on the valve cover. I change my air filters annually.
Next time I replace the filters I will pull them both apart to see if there is a noticeable difference in dirt/oil build up inside each.

Jan 2nd, 2018, 20:08	#1
Groundes-Peace Master Member Last Online: Mar 14th, 2024 17:23 Join Date: Jun 2009 Location: Milton Keynes	Oil breather pipe; rocker cover to air filter Please explain what is the benefit/purpose of this arrangement versus having a filtered cap on the rocker cover....?

Jan 2nd, 2018, 20:27	#3
Ron Kwas Premier Member Last Online: Today 00:11 Join Date: Jul 2007 Location: Connecticut, USA	GP; It's a variation on PCV system. Both provide fresh filtered air for PCV system, but when sourced from Air Filter, even during high crankcase pressure situation (high RPM, high blow-by) when crankcase pressure exceeds the rate of extraction by flow-limited path to intake manifold, crankcase gases would not be allowed to escape to atmosphere (and allow oil droplets to make a mess of the Valve Cover), but would be routed into Air-Filter where they would be sucked into carb intake (and when excessive, foul the Air-Filter, choking off front carb air). See also: http://www.sw-em.com/pcv_diagrams_and_notes.htm Cheers Last edited by Ron Kwas; Jan 2nd, 2018 at 20:29. Reason: Added Link

Jan 2nd, 2018, 20:19	#2
Derek UK VOC Member Last Online: Apr 18th, 2024 17:06 Join Date: Jul 2006 Location: Chatham	With the later routing of the ventilation hoses the pipe from the air filter feeds clean air into the engine. The cap doesn't do anything with this routing and is just an oil filler cap. i.e. the direction of the air is from the filter into the engine.

Jan 3rd, 2018, 12:42	#4
Groundes-Peace Master Member Last Online: Mar 14th, 2024 17:23 Join Date: Jun 2009 Location: Milton Keynes	Ron, Thanks for the attachment which I had not seen before. In my case when I had my engine rebuilt, I just had the basic filtered cap on the valve cover. However when I used the car on fast runs there was quite a quantity of oil misting on the valve cover. I then went for the hose return route into the front air filter, which overcame the messy build up on the valve cover. I change my air filters annually. Next time I replace the filters I will pull them both apart to see if there is a noticeable difference in dirt/oil build up inside each.

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