cutlassdriver61

I have a 72 cutlass. I've had it for about 2 years now and when I bought it, there were silver "oldsmobile" valve covers on it. In the trunk, I have the original valve covers. There has been a pretty bad oil leak for a while now and it looks like oil is coming out of the filling tube. I think it may have something to do with the valve covers on the motor now. The original valve covers both have air holes for PCV hoses to aid in breathing.

My question is... Does anyone know exactly why the oil may come out of the filler tube?? Is it because the "custom" valve covers on it doesnt allow the proper air circulation? And would the solution be to put the old valve covers back on?

z11375ss

I might even run the motor without the valve covers on to see what it does. You definitely have a pressure problem in the crankcase. The new valve covers not having breathers or breather on one side may be the problem. How hard is it to change them. Not much. I say give it a try, it can't hurt. Other than that I cant think of why there would be positive crankcase pressure enough to blow oil out of the filler tube of all places. It also may look to you that this is the source of the leak. Clean the motor and watch where the leak is coming from. It may be it is the intake and just looks like the filler tube. Good luck in the sub zero weather.

W403

Although there could be many reasons for this, here are a few things to check. Considering the engine is in decent working order and knowing early olds blocks are pretty tough, try these recommendations. Ensure that the PCV valve has the correct vacuum rating for your application. If any components have been changed;camshaft, headers etc, you may need to experiment with different PCV valves by they're vacuum rating. PCV valve in one valve cover hooked to the correct vacuum source and a vent hose from the other valve cover to the air filter lid. With the PCV valve hooked up to the carb vacuum source check the PCV valve opening vacuum with a gauge and the engine running. I understand this does not compensate for engine load but will help dial you in on what vacuum it's opening at. Also the valve guides could be worn as well and causing blow by. As well, you may only need to either reinstall the correct valve covers in case the chrome units do not have an appropriate baffle for the PCV if yours are leaking at the valve cover connections. The latter being the simplest, and the one I have corrected on many cars some of which I had to use double gaskets for rocker clearance ( they were rubbing on after market units and no replacements available at time) sealing them overnight with aviation cement ( don't laugh, it worked..heh) and longer valve cover bolts. I also used an aluminum can to make a baffle so oil wouldn't get sucked up into the PCV and making it smoke which was the case for repair) Don't forget to use an inch # torque wrench if all possible and torque from center out per spec slowly, I've never had a comeback using this method and prefer it done right the first time. Good luck.

88 coupe

Do it, then let us know what happened.

Norm

W30post

Is the oil coming up from the base of the fill tube or the top. There is a baffle in the oil fill tube that may have been left out during a timing chain change or a rebuild. You can check this by running a very long bar down into the fill tube. You should get stopped just below the water pump/ fill tube deck height by this oil shield.

Just something else to look for.