Oil droplets through vented oil cap

[DJ0416]

Hello,
  I have a 67 De Ville Convertible with a open positive crankcase ventilation system.  I notice oil coming
through the vents of my oil cap and collecting on top of the motor.  I replaced the PCV valve thinking that
may solve the problem but it hasn't.  I notice it when I'm travelling around 55MPH. Looking for any advice
on potential solutions.  I'm assuming I have a blow by issue but it's only a guess.  The motor is a 429Ci.

Thanks
Don

[bill06447]

It's usually because of excessive blow-by overwhelming the PCV system or some fault elsewhere resulting in reduced vacuum at cruising speed, either vacuum leak or timing issue. The intakes on those are notorious for cracking at the runner/head flange, this would cause a vacuum leak as well. I'd hook up a vacuum gage with an extended hose and take it for a drive

Bill

[TJ Hopland]

Have you changed brands or weights or additives in your oil recently?    I have noticed that different oils, even additives can cause a change in that build up.   Early in the zinc panic days I was using I think an Oriley parts brand magic zinc stuff that seemed to cause that in all 3 engines I put it in.   Quit using it and it went away.  One engine did it when I was using a diesel oil.   I am now using a different brand diesel oil in it now and its fine.   Oddly the problem oil was a big name premium brand what I have been using for several years now is a store brand.   You would think the store brand would have more fillers and crap in it than the big brand.