Oil breather & Valley Gasket Advice

[chris1972]

I cleaned out my oil breather as there was a slight weep of oil appearing behind the dizzy from the valley gasket. After removing the hose from the top of the breather, I can clearly hear the air travelling through the plenum down the hose, but I'm not feeling any vacuum/ suck when I place my hand over the end of the hose. Does this mean my valley gasket is cream-crackered or is this normal?

[chris1972]

Bump...

[phazed]

There should be vacuum from the plenum tee piece, more at idle then at speed.

This is to suck out the fumes from the engine and cycle them into the combustion chambers to burn them off.

Make sure all pipes are clear, flame trap and mushroom are clean and clear.

Spends your man for full breather system operation and benefits.

[chris1972]

phazed said:

There should be vacuum from the plenum tee piece, more at idle then at speed.

This is to suck out the fumes from the engine and cycle them into the combustion chambers to burn them off.

Make sure all pipes are clear, flame trap and mushroom are clean and clear.

Spends your man for full breather system operation and benefits.

Thanks Peter

What is the mushroom? The pipe looks a little dirty inside, but doesn't seem blocked. If I replace the valley gasket, do I need to remove the rocker covers or is it only the plenum and plenum base?

[SILICONEKID350HP]

phazed said:

There should be vacuum from the plenum tee piece, more at idle then at speed.

This is to suck out the fumes from the engine and cycle them into the combustion chambers to burn them off.

Make sure all pipes are clear, flame trap and mushroom are clean and clear.

Spends your man for full breather system operation and benefits.

Peter do you have ay pictures of your instalation ? cheers .

[phazed]

Don't think I've time to fit the "Spend" version before Saturday but when I do I'll post it up.

[cureton]

Question related to this topic: What size/diameter should the breather hole in the "mushroom" be like? Looking at my car, it seems a bit clogged. Just poke a needle in or take a decent drill...?

[phazed]

Mine hasn't a mushroom.

If in doubt, renew it, they're cheap.

[chris1972]

phazed said:

Mine hasn't a mushroom.

If in doubt, renew it, they're cheap.

is the mushroom the small filter on the opposite rocker cover to the breather?

[phazed]

Yes

[spend]

I think that mushroom causes too many problems TBH. I am convinced the good ones have some kind of valve ~ I have a couple that are good and you can definitely only suck through them - blowing just fills your cheeks. Whether they are an early part & later ones just have a straight through hole I have no idea.

Th easiest solution is to follow Peters implementation (which is forced on him because he has later 4.6 rocker covers) that mirrors the Rover development of taking the input breathing from close to the air filter - ie take a small bore pipe from the rocker cover and tee it into the large induction pipe as close to the air filter as possible. You can then have a larger bore pipe stub into the rocker box & pretty much maintenance free peace of mind.

I can only think that breathing from lower pressure at the air filter rather than atmosphere must help with the associated problems long duration cams cause with the PCV (as designed by Rover for their std cars).

[chris1972]

Thanks (both Peter and Spend). Peter do you have a pic of your mod?