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Post by paddymk2 on Jul 16, 2017 4:29:02 GMT
Hi there, Looking at other posts and pics of car engine bays I noticed the arrangement for engine ventilation appears quite different. Most cars look something like this: ith the PCV just in front of the carburetor. Looking at the components diagrams it appears that the blowby gases are drawn out via the oil separator through the PCV and into the inlet manifold. The arrangement on my car is as below. The port on the inlet manifold is plugged off. While the output from the oil separator is connected to via a hose to a copper tube dangling down to the underside of the car. I can see that when the car is driving fast there might be some draw through that hose - but not like the airflow at the manifold. Question:should the PCV also be connected to the valve cover? Or is there another ventilation to the valve cover? Regards Paddy
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Post by dave1800 on Jul 16, 2017 9:40:06 GMT
Oh dear! That's how the crankcase was vented before PCVs, straight into the atmosphere. The fumes were sucked out at speed by the venturi effect. This was quoted as being one of the major contributors to pollution. The UK crabs Mk1 /Mk11 used the PCV. There were two different tappet covers and separators. Mk111 cars did away with the PCV and vented into a constant depression inlet in the (later design)carbs - the same system used by MGBs from around 1970 when they dropped the PCV.
There should NOT be a vent to the rocker box, the whole idea is to create negative pressure in the crankcase and this aids the proper lubrication. This relies on using the correct oil filler cap with the right size vent hole and filter. You will also find it difficult to adjust the carb without the closed system as it affects the mixture especially at idle.
Hope this helps
David
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Post by paddymk2 on Jul 17, 2017 14:11:40 GMT
Thanks Dave, I also came across this at the Bluestreaksix site: www.bluestreaksix.com/austin1800/Page11.htmlENGINE VENTILATION
The correct operation of the ventilation assembly near the carburettor on manifold is essential to prevent crankcase pressure build up and oil leaks.
Clean thoroughly and fit a new diaphragm (as used in the four-cylinder Landrover).
If you use a sealed cap or seal the old vent hole under side filler cap with a self-tapping screw, the engine will have a slight internal vacuum. The engine ventilates all right and there is absolutely no oil leaks.
This method has been tested on at least ten cars over a period of five years.
Does that approach make sense to you and is the normal plastic filler cap adequate? And is there a good source of components you could recommend? Regards Paddy
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Post by dave1800 on Jul 18, 2017 0:51:06 GMT
I would suggest using only the correct vented cap; the vent hole size determines the appropriate vacuum and airflow.
regards
David
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