Hi folks! Have a '78 F-150 with a 400. Oil is getting sucked out through the PCV valve. Not too good. A friend of mine who owns a garage said he remembers the old Ford's having this problem and the valve covers were redesigned to prevent the motor oil from being sucked back out through the PCV valve. He can't, however, remember what years were affected and whether or not aftermarket valve covers correct the problem. Anybody ever hear of this? Will a set of aftermarket valve covers fix it? I've owned a bunch of these old Ford trucks and have never had this problem before. Thanks!

 

I believe they corrected the issue with a bafflle looking thing that goes under the PCV valve. To answer your question i would think aftermarket covers should correct the problem. I have a 78 with a 351M and have not experieced that but ive heard of it.

 

Replace the breather filter in the air cleaner.

 

Someone had suggested changing the breather filter, so I did, and it didn't help.

 

Check that the PCV valve is operational. Most times if it rattles, it is OK. Does your motor burn oil at all? Often PCV leakage issues are related to piston ring clearance. If you have the means to do so, it wouldn't hurt to do a wet and dry compression test.

 

PCV valve is operational. No, the motor doesn't burn any oil at all. The motor is a Jasper with only 6,500 miles on it, so I doubt it's the rings, but I'll do the compression test and see what I come up with.

 

I can only assume the valve covers are the same for the 1970 and up 351 Cleveland, 400, and 351M engines. I had a 1971 Cleveland, and had different 351M and 400 engines throughout the 70's vehicles. None of them exhibited oil being sucked through the PCV valve, so I doubt there were any changes made. That doesn't mean that your vehicle's valve cover hasn't been modified, or that the baffle hasn't sustained some kind of damage. Try another valve cover from the junkyard and see what happens, or remove the one you have and closely inspect the area underside of the pcv hole. With all the oil splashing around at higher rpms, a small crack in the baffle or a weld may allow oil to pass through into your air cleaner. This might look like a severe case of blow-by, which I hope a fresh rebuilt engine wouldn't have.

 

I think the first thing I would do is pull the valve cover and see if the baffle is in place. If it is I would then check the rocker arms and make sure somebody didn't leave the oil deflectors off. Man if they left the oil deflectors off of those rockers arms they will spray oil everywhere but where it is supposed to be

 

When I put the old school Mickey Thompson vc's on my 400 I had to make larger baffles to keep the oil from pushing past the breather on the driver's side. I'm sure that my pcv was also getting the over oiling treatment.