I just repalced the my valvecovers with cast aluminum covers from Eddie Marine. No breather vents. Oops. I'm not really much of a mechanic, and I would have hoped the mechanic at the marina that did the work would have noticed and said something. He didn't. I ran it good and hard today. Oil pressure was OK when at thottle but at idle the pressure was almost zero. I shut them down and checked the oil. The was a loud sucking sound through the dip stick, (I had created a vacuum in the crankcase) and very little oil.

Where did the oil go? Did I ruin anything? What do I need to do about ventelation?

I put oil in, and they were running fine back in the slip with the oil filler caps out.

Thanks

only two places it can go, in engine compartment or in engine cylinders. I would bet it cam around the rings and was burned in chamber, check for fouled plugs, sounds like there is oil getting around rings... and a lot of it...

dean is right, with out breathers the cylinder blowby have to pressurize the crank case and will usually blow out seals and will be sucked into the cylinder during the intake stroke, very suprised that who ever put them on looked the other way when installing ( couldnt miss it, two hoses coming from flame arestor,"where do these go??? well I'll just remove them no one will notice.... )

I just cant understand selling valve covers without breather holes...What are you supposed to do for crankcase ventilation ?

You can always buy the aluminum add on vents that you have to drill a hole in the valve cover and bolt these on. Some valve covers come that way for custom set ups. Via exhaust clearance problems, shift brackets, superchargers, etc. Its not that big of a deal as long as you do put vents in.

like these...

I hate to take a brand new set of powdercoated Valve covers & start drilling holes in them ! Knowing how my luck is..

I need to order a couple sets...I'll call Fred & see if he can get me fixed up

I purchased the same valve covers several years ago, and yes you have to drill holes in them to accomadate your particulair setup. I brought hoses up to the flame arrestor, but I had to purchase the Moroso rubber inserts for the holes to protect against excessive oil splash sinch the Valve covers do not have a baffle in them. Needless to say, crankcase ventilation is very important no matter how you accomplish it.

We recommend venting both covers on marine applications. You can drill a hole and use a baffeled grommet or you can have the aluminum baffled tubes welded on and use 3.5" breathers.

I have the same valve covers on my boat. And I used the tall breathers on both sides. Works fine.

In a 540 would one single vent as shown in the photo be enough? Opinions Please.