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TommyK

Crank Case Ventilation

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TommyK

On my 5212.5's Briggs two opposed.

There is a hose that runs from the bottom of the filter house to one of the valve covers that doubles as a crank case vent valve, of sorts.

The latest replacement of leaking gaskets revealed that the fiber disk inside the breather that covers the hole has deteriorated. Chunks of fiber disk have chunked off making it impossible for this stiff disk to seal up the hole. While she runs fine, I suspect that it may not be good for the engine in the long run as all B/S engines have this feature in one way or another.

I suspect, given the difficulty I had getting just a crank seal for this vintage Briggs getting an exact replacement may be difficult. Especially since this valve cover triples as a deflector to keep the cooling air close to the engine as long as possible. My guess is this was purpose built for this specific vintage of engine.

I've opened it up, and the disk is captivated by a bracket that is spot welded in place, so it is not intended to be serviceable. However, given it's age, I need to replace this disk. I figure if I can drill out the spot weld, then pop rivet it back in place, I can service is unserviceable item. My only question is does anyone have a suggestion for replacement material for this fiber disk. Is it fiberglass? It has the look of Masonite, but you can see a fabric within.

I've pondered fabricating one out of plastic, like that of the straight side of an engine oil bottle, but I'm not sure it would withstand the heat.

Another idea is procuring a fiberglass repair kit, soaking the mating in resin, then when cured, trimming to fit.

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hurleyii

Well it can't be fiberglass as that's not really a breathable product.

My guess is it's purpose is to allow the engine to breathe and at the same time keep oil from rerunning out of it and into the vent tube going to the air cleaner.

My suggestion is if all B/S engines have it is to buy one for a new engine and do whatever is needed to make it fit. It's also very likely something simple as that the design has never been changed. It's also possible a new valve cover would be available do to that piece or whatever reason even if it's unlikely I'd check.

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TommyK

The fiber disk is not meant to permeable. The mode of operation is that suction from the air cleaner pulls this disk open, thus drawing some air from the crank case against a spring that is keeping it closed. Modern cars have a PCV(Positive Crankcase Ventilation) valve, I think this is similar. The spring (I forgot to mention the spring) is captive with the disk inside the breather/cover. Every B/S I've known has this feature. In some the breather/cover is plumbed to the carb, but they all have this disk, visible once the breather/cover is removed.

My first order of business is to see if this is a currently available item at a reasonable price or unobtanium. At which point, a field fix is in order. I'll keep you posted. In the interim, ideas for replacement disk material is appreciated.

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