Guidance on Volvo B20B Engine Ventilation System and Manifold Restrictors

Phil142S

HI Guys,

I am looking for some detailed guidance regarding the crankcase ventilation system on a Volvo B20B engine. Specifically, I would appreciate clarification on the correct ventilation cycle and how the various hoses and fittings are intended to route.

I am also trying to understand the purpose and placement of the manifold restrictors—where each restrictor should be located, which pipes they belong to, and the components or ports they should connect to.

Any diagrams, descriptions, or practical advice on how these connections are designed to function would be extremely helpful.

Thanks

Major Ledfoot

What year is your B20B? And, what carbs are on it?
SU HS6
or
SU HIF6
or
175 CD 2SE Strombergs?

That will dictate the plumbing arrangements.

Phil142S

Hi,

1972 142s - twin 175Cd's

Major Ledfoot

Okay, here's a diagram of the hoses from the Green Book.

Image description

940Person

Major Ledfoot

My b20 with twin stromburgs is setup this way. Note the tube from the oil full cap to intake manifold has a very small hole at the manifold. If you go without a restriction here the engine will suck up and burn lots of oil.

jamesinc

I'm glad I'm reading this now, I have @paul0075's B20B on the stand while I sort out the vacuum ports and I did not know it wanted a restricted port!

I looked up the parts manual and it is Volvo part # 460082

Phil142S

Hi,

Thanks for the diagram and replies.

Currently my motor has been set up with the PCV breather hose connected to the large opening connection of the manifold.

The oil cap is connected to the carby and the brake booster hose Connected to the restricted connected to the manifold.

I don't thinks this combination is helping my motor.