The Stovebolt Site Forums The Shop Area Engine Shop Proper PCV source needed

Hi,
I am going ahead with an aftermarket PCV installation. I plan to remove the oil breather at the bottom of the engine and replace it with a frost plug. The frost plug needs a hole in it to accept a 1/8" male npt fitting. I have seen 1/8" on PCVs in bubble packs, but I don't know which direction the PCV flows. I know it should flow to the intake manifold and "stop" the flow back into the engine. I also don't know what orifice size the PCV should have to allow the proper amount of flow. I think I'll just put a "T" at the intake manifold port so I can still have the wipers and the PCV. Thanks - Scott

Scdascda
you might look at some newer sixs to get a better idea how to set youres up

I did PCV's on my 2 261 engines just recently. Used a PCV valve from a 75 250 6. Drilled a 3/4 inch hole in the valve cover,used a typical GM grommmet for the valve. I also welded in a sheet metal baffle under the PCV hole and stuffed it with copper steel wool like stuff to strain out the oil from getting sucked in.The one on the modified 261 blew oil out the breather over 4000 rpm, so I cut and welded up the stock draft tube, fitted a K&N as you see in the first photo.Uses a non vented cap on the oil fill, problem solved.The last photo is the reasonably stock 261, no problem with this , never revs that high. The PCV addition slightly leaned out the carb mixture slightly at normal speeds, ie,high vacuum when the valve is sucking.Not a problem on my trucks with Holleys may or may not be a driveability problem on another engine.
Side breather
PCV valve
More stock setup

Looks good Tony!

Splash, I designed the system on the 37 after the photos you posted of the PCV on early GMC engines.
On the PCV valves, the one on my 51 truck now uses a valve from a 2.8 Chevy V-6, the 250 valve created too much suction in my opinion on that engine which has 20 inches of vacuum at idle, the 37 engine has 17 inches with it's hotter cam.Purolater PCV valves are marked by flow with a letter on the valve,other brands seem to use one size valve for many applications.
The valve needs to create a negative crankcase pressure at idle, but not too much, it's a trial and error situation, playing with a handfull of two dollar PCV valves.While my 4.3 powered S10 was idling, I placed my hand over the ventilation air intake on the valve cover, then pulled my hand away and listened to the "sound" of suction. I then duplicated the "sound" on the two Stovebolts.Crude home brewed engineering that works well in my opinion.

Dang Tony ~ you need to borrow my truck if it'll cme back looking that clean ! .

I like the bent up pipe , looks very nice & stock

The old AC Delco training taught us to lay a bit of shiny paper (magazine page) over the open oil filler , engine at idle - it should suck smartly in place but blow off when you rev the engine ~ also crude engineering but GM approved ! .

It has been a while since I have done his stuff, what is he advantage of a PCV valve?

I understand the recycle of the gasses into the intake manifold for combustion makes the engine run better. It also smells nicer when your vehicle is running. And, if you configure it right, you won't get that dripping on the floor from your breather tube. (I plan to eliminate the breater tube in this PCV installation process) - Scott