PCV on a V6 ?

[5500 GMC]

Anyone know if there was a Crank ventilation set up on the stock 351?
attached picture shows what i have done to ventilate
i have round rubber grommet in valve cover and the breather cap fits tight but there is oil leaking out around the grommet because the hole is for a twist and lock type cap
if ventilation is not needed i can just put a filler cap in and no more oil leak

[bigblockv6]

It all depends on the year of the engine, what I see in the pic you posted is the setup that was used on all GMC V6 engines from 1968-74 and by the looks of the valve covers they are 1972 style. 1966 and earlier had the breather attached at the back of the engine block, in 68 that was capped off and the breather was moved to the valve cover. Leaking may me due to the valve cover was stamped out for a breather that fits on like the oil cap and has a gasket, you just need the right breather.

[bigblockv6]

Here are pics of the correct factory breather that was used from 68-72, 73-74 used basically the same breather but it was a push in type because the valve cover was stamped out for a grommet. It is important to keep a breather on your engine and not just cap it off,the system will get pressurized and will blow the main seal. There are PCV valves threaded to one of the intake ports in each cylinder head and to service those requires removing both valve covers.

[5500 GMC]

bus is a 1969 the engine was rebuilt before i got it, just assuming it was the original
the local parts store could not find one like that.
i guess its time to look elsewhere
PCV valves in the heads, interesting i will have to check them out
THANKS for the info

[bigblockv6]

If you can't find one I may have an extra that's chrome.

[Paul Bunch]

How often should the PCV filter be changed in a 64 305E engine and where can I find a new one?

[Nate]

In the GM engines that had the PCV on the outside of the engine we checked them at each oil change, this sounds a bit excessive being that the 305E has them under the rocker arm covers. I bought my PCV for my 305E at NAPA, if you need a part number let me know and I will look it up in my records

[bigblockv6]

There's two PCV valves threaded into each cylinder head, it sounds like Paul is looking for the crankcase breather filter that goes on the back of the engine.

[lizziemeister'sV6]

There is 1 PVC valve threaded into each head under the valve cover - not 2 in each head as posted in the proceeding post - in 1966 and earlier V6's - behind the left valve cover in the block itself is a filter can pressed into the block with a screwed on lid that houses a paper element. Both PVC valves and paper element can be purchased at reliable parts stores.

[Paul Bunch]

Thanks for the help with the pcv filter and I was refering to the one at the back of the engine on the drivers side that has a replaceable element. Now if I can find out what later model 5 or 6 speed transmission will work in it I will be happy.