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Crank case breather


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Recently added a oil separation tank to the rocker box cover breather on my GT6 Mk3, Ive noticed that with the engine running the oil filler cap on the rocker box is difficult to remove due a vacuum which is coming from the tapping on the inlet manifold that's used in the oil separation pipe circuit. If the pipe from the inlet manifold is clamped closed then the vacuum stops and engine rpm drops on tick over which to me indicates that there is something wrong in the way ive piped the system to the engine. The engine has been stripped and overhauled so all the original pipe's were removed and dumped so i had no reference installation to use which i why i think i may of got the pipes fitted incorrectly.

My question is hs anybody fitted an after market oil catch tank in the rocker cover breather and if so whats the correct way to pipe it in.

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sounds like you have connected it to the high vacuum port on the manifold which is too high and will actually increase oil consumption by sucking vapour through the tank.
I have two large bore breather hoses,one from the rocker cover and one from where the original fuel pump was,both to the separator tank and then a hose from the tank to the atmospheric side of the intake between the air filter and inlet manifold.
there should be a take off on each carb for the breather hoses which will be at a much lower vacuum than connecting it to the one I think you have.

but as iain said a pic may help.

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Quoted from esxefi

Quoted from Alfie
What is the high vacuum outlet used for?

normally used for a brake servo but if you don't have one fitted just fit a blanking plug.

On earlier engines (mk1) the manifold tapping was used for crank breather but with a regulating valve in between.

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