Cam Cover breather

[seniorchristo]

Me again. My cam cover has a breather hose which runs to the Weber carb airbox. It recently started spewing oil which is accumulating inside the box. Is this a common modification? My thought is to put a baffle inside the cam cover to keep oil which is thrown from the chain, out of the breather hose. Is running the hose to a catch can a better idea? Help appreciated.
Thanks,
Chris

[elancoupe]

The breather is a common mod on uprated engines, I have mine routed to a catch bottle.

[seniorchristo]

Elancoupe
Do you get a noticeable accumulation of oil in the can? Do you have a picture of your arrangement?
Thanks
Chris

[gjz30075]

"recently started.." would have me believe it was fine before. Maybe you have some broken rings which
will increase crankcase pressure to allow this to happen. Run a leakdown test to determine what's what here.

[elancoupe]

Elancoupe
Do you get a noticeable accumulation of oil in the can? Do you have a picture of your arrangement?
Thanks
Chris

I do see a little in the bottom of the tank, not enough to worry about.

I run a simple, generic breather tank with 2 inlets, one for the cam cover breather and one for the breather at the back of the head. I never liked the factory ideas of venting it into the airbox, or down on the chassis via the road tube.

Greg has a point, if something has recently changed, it may be worth investigating.

[rgh0]

In my Elan I run a front crank case breather as shown in the pictures to a TTR lightweight fibreglass catch tank that fits in the triangular body section in front of the passenger foot well. I don't have the rear head breather as I use the McCoy Stromberg conversion heads where this facility is removed with the machining to fit the Weber manifold.

In normal road style driving no significant oil accumulates in the catch tank just a little blow-by gas condensate which is mainly water. When racing and using continually 8000 rpm + revs I will get a couple of teaspoons of oil/ condensate mix in the catch tank after a race weekend.

If you are experiencing excessive oil in the air box in normal driving you potentially have excessive blow-by gas flow carrying excessive oil into the air box. This is typically due to worn or broken rings or worn bore and pistons


cheers
Rohan

[seniorchristo]

Thanks all for the advice. I'll look into the blow by issue.
Chris

[seniorchristo]

I have finally gotten around to resolving this issue. I installed an oil catch can (see pictures). Blow by from the crankcase goes to a baffled catch can where the oil is accumulated. The remaining vapor then continues to the original airbox port. The accumulated oil is an oil/ condensate mix.

Leakdown results: cylinder supply pressure cylinder pressure
#1 100 psi 93 psi
#2 100 psi 97 psi
#3 100 psi 94 psi
#4 100 psi 95 psi

From my understanding these leakdown results are within acceptable limits. Comments appreciated.
Thanks, Chris

[alan.barker]

if you pressure test cylinders dry and then wet what pressures do you get.
For me you only need to test to see if rings are o.k. Not a leakdown test which also checks valves
Alan