Importance of pcv/breathers

Mitty

Regular user
Hi, just a little story really. When I changed my rocker covers, I removed the blank and installed a breather on the left cover, and swapped the pcv valve on the right cover for a fancy looking one. Hadn’t really driven the car since, and with the weather like it’s been have put a few miles on the 74. All this was based on online opinion that a breather, not a blank should be fitted.
On initial start up Saturday morning, it was massively over fueling, I put this down to being sat for a while, and it cleared after warming up. But, the idle wasn’t right, but drove ok.
Sunday morning, same thing, so I figured something was up. After a bit of research, I found conflicting opinions on breathers and blanks. I pulled the pcv valve off, tested it, and it was open all the time. So i refitted the old pcv and blank, and hey presto, cars running perfect again.
For aesthetics I’ve blanked the breather I bought, and put a new pcv in the other fancy case.

Moral of the story, just because you can, doesn’t mean you should!

Tim.

675499-BD-9475-458-D-A4-B0-19915-CA2853-F.jpg
 
Last edited:

kentvette

CCCUK Member
That's a fab looking and, envy inducing engine bay!:sick:

And a very relevant warning re the PCV (Positive Crankcase Ventilation) valve.(y) Many years ago I was collecting service parts from our friend and Corvette mechanic guru in California. He had prepared the list of "wanted" items before we drove to the (huge!) AC Delco parts warhouse. Among them was a PCV valve. I made the mistake of questioning the need - after a brief lecture I realised just how important a functioning valve is and, that not all valves are the same. The up-shot was that I bought a couple, so as to follow his advice and change it after a few years or so.

I know of a few cars who's owners complain of high oil usage, almost certainly the result of a non functioning, or not existent PCV valve or system.:rolleyes:
 

curious bystander

CCCUK Member
I had a top overhaul done on my engine by a well know Corvette mechanic. For some reason he decided to neaten everything up on the rubber pipe front and installed a PCV on BOTH sides of the engine.
Well it looked neat but without the passenger side having an open breather the engine struggled to tick over.
I never found out why a Corvette specialist made such a basic error:unsure:
 

CaptainK

CCCUK Member
I too had PCV issues. Previous owner had put "shiny" big capped PCV valves in it. Looked nice, but the bugger used a lot of oil and kept blowing the driver's side one off when out driving. So I got some new "original style" ones and not had any problems since.
 

Roppa440

Well-known user
I've always preferred to put the PCV valve on the left side and breather (air intake) on the right because Chrysler swapped to that way around on most of their V8s in the late 60s/early 70s when they found emissions were slightly better that way. Which suggests to me they were burning less oil. On big block mopars when people have made the mistake of not using breathers or a PCV system the tin valley tray cover under the intake manifold inflates up with the crankcase pressure!
 

kentvette

CCCUK Member
I don't know if all year small blocks (68 - 82 that is) are teh same, but the PCV valve is on the left bank valve cover on '78s, 79s etc...
 
Top