Pintel valve and positive crankcase ventilation.

[Keith Clements]

PJGD ( philip) kindly provided this patent application buried in a long topic, so I thought I would repost as many people ask about how it works.

download/file.php?id=26612&mode=view

This shows how progressive Jowett and Gerald were in using new technology 10 years before other British manufacturers.

viewtopic.php?p=42613#p42613

[Tonyb57]

Interesting topic, my engine in still on a trolley, never been fitted since the 70s, the valve in question on my 48 has a pipe that goes round and under the oil filter to the right hand pushrod chest cover, the felt breathers are intact and free

[David Morris]

Hi Tony,

Yep, that's the famous pintle valve. The links before give you some good information, although some of the illustrations may not reflect your valve. The valve can be removed from the engine quite easily, as it unscrews from the oil filler tube. Once in your hand, it doesn't look as if it can be dismantled, but it can. If you hold the large hex nut at the end of the valve that goes to the copper pipe in a vice, the other end, also hex, can be unscrewed, but it will be tight! It probably hasn't been undone in 70 years! Inside, you will find the pintle held inside the valve and a coil spring. Where the valve seats onto the body there should be good clean surfaces. If they are pitted, these need polishing to give a good seating.

There used to be lots of discussion over this valve. People were chopping parts of the spring off, or inserting washers to increase the spring tension. You may find yours has been 'broggled' in the past, with parts added or missing. The valve was quoted as the root cause of lots of engine faults. Personally, I think this was incorrect and people grasping at straws in desperation! If the valve seats are polished and the valve reassembled as per the factory, I believe it works correctly, without any, so called, modifications. Although you may need to compare the spring length, with a spare one, to make sure you have the right length and that the spring hasn't been 'chopped' in the past? By the way, the valve is a commercial part, made by AC and fitted by Jowett's. It is not unique to Jowett's. JCS might have new ones?

All the best,

David

[Keith Clements]

To avoid confusion, the aim is to make the pressure in the crankcase slightly LOWER than atmospheric to give POSITIVE ventilation rather than on other cars that vent the POSITIVE pressure created in the crankcase due to piston ring blow by into the atmosphere through some form of catchtank to catch any oil mist. If the valve does not close or there is excessive blow by you will get blue smoke out of the exhaust. If the valve does not open then there will be oil coming out of every oriface and the mechanical petrol pump may fail. The pump is operated by a push rod from the distributor drive but relies on a spring to return the diaphragm after the push, so positive pressure in the crankcase might stop this return. The latter may also happen if the valve does not close at the correct slight depression and so the petrol pump diaphragm is unable to create a suction as the diaphragm is sucked back even though pushed in.

[Nick Webster]

As David points out, it is a commercial part made by AC. Funnily enough one of the few other places I have seen one fitted was on a Vauxhall.... but then Gerald Palmer once worked for them too!

Nick

[Keith Clements]

Tony, The usual route for the pipe is through the gap between the distributor and oil filter rather than the other side of the distributor. It is a bit tight through there but looks neater.