Have a question. I got a '77 460 with one of those oil fill breather caps. The old one was saturated on the inside with oil so I replaced it. The bottom prongs on the aftermarket cap are not that sturdy and whenever I tried to connect the hose from the cap to the air filter assembly it made the cap pull up from the valve cover(the prongs bent). Well I went and bought a little filter to put over the elbow at the cap so I would not have to run it to the air filter assembly. Seems to work fine but heres my questions. First do I need to keep this as a breather cap or can I replace it with a regular cap. The reason I ask is that I have the typical cold engine good oil pressure as it gets warmer pressure drops. I noticed the other day that there was alot of white smoke coming from that little filter on the cap after the truck had been taken out for a short drive. Before I replace the cap the stock oil pressure gauge always read a little on the low side but I know this does not mean anything. After I replaced the cap the stock gauge read about half at start up and then slowly went down, again know that means nothing. Put an aftermarket gauge on reads around 50 at start up and have seen it get as low as around 5 after some driving. At the time I noticed the smoke from the cap filter, pressure was around 25. I guess I'm asking am I losing pressure through the cap and can I just put a regular oil cap on or will it cause problems or do I have to run the old cap back to the air filter assembly? Thanks for the help.

 

pressure loss when warm is normally bearing wear, are you still using pcv valve ? if so is it working ( rattles when you shake it) if all OK then you have ring blow-by, then it's time for a rebuild.

 

Yeah I figure I am gonna have to rebuild the engine in the near future but what I am actually wondering is if that breather cap is really necessary or can I just put a regular non-vented cap on or am I possibly getting a slight false pressure reading because the cap is no longer running into the air filter assembly. The amount of smoke coming out of that cap seems a bit excessive to me but then again I have never had a vehicle with an oil cap like this before.

 

if the pcv valve is working and no excessive blow-by you won't get much if any smoke, you can just get a regular vented breather to replace what you have - maybe another make or model in the boneyard will have what you need. Using a heavier oil will help prolong the engine life .