1969 305E crankcase ventilation and PCV valve.

[1969_CM2590D]

I was looking around to get ready to adjust the valve lash and check the PCV valves. I did some searches on those things and a couple of questions came up.

The truck is a 3/4 ton, non-California. It's free of emission controls other than the PCV's in the head, and the breather cap in the valve cover. So, I think this is the last of the line before Thermacs and air pumps on all pickups.

First one is, I see a lot of references to a draft tube or a breather/filter on the rear of the older engines. Nothing is on the back of mine, but there is a breather that is on the rear of the passenger's valve cover, plumbed into the air cleaner. Same function, I assume? The ventilation schematic just calls out the PCV's and the breather, showing the airflow.

Second, on the searches I found two numbers for PCV's. Other than having a threaded end, they look quite different, but are they? These look like they have a provision for a hose or something opposite the threads, while mine looks like a piece of pipe threaded at the bottom with a 9/16" hex head at the top to extract it. The PCV itself seems fine, rattles freely, spring has tension, and seals when you blow air through it- So do I really need to change them? The GMC manual says do it every 12,000 mi. regardless.

Picture below.

Thanks

[bigblockv6]

Dennis, the pcv in the pic is the standard type OEM from GMC, back in the day you could buy these from the dealer as well the other type which was the AC -CV623C, which was still available through the late 90's maybe even early 2000's. NAPA has two types that fit the V6 application, part no 2-9254 and the other if I can remember is 92508, I'll check to verify if that's correct or not. As far as the breather, in 1968 it was relocated to the back of the passenger side valve cover and the old location was capped off with an expansion plug.

[bigblockv6]

Dennis, ok the correct part number for the other NAPA pcv valve is 9258.

[1969_CM2590D]

Thanks! Yes, I saw those earlier. Is there any difference in them other than the finish and $2.70?

[bigblockv6]

They differ in the way they look but serve the same application but so did the GM versions, so it all works.

[1969_CM2590D]

Good! I like it when it's OK to be cheap.