304 ventilation

[shum8]

Ok - I have searched here and the web a good bit today..... and have found several "correct" crankcase ventilation methods. Bad news none are exactly like mine before I tore it apart. Now that the chassis is done, I'm into making the smaller final connections - vacuum lines, coolant hoses, etc. here's my dilemma:

The intake I have is an Edelbrock Performer, non-EGR version, and when I got it, the PCV valve port (at least what I believe it to be) was blocked with a freeze plug, the vented oil filler cap was connected to a vacuum port at the base of the carb with a PCV valve in line, and no valve cover venting.

Based on my snooping around, popular belief is that the oil filler vent should allow air into the engine, the PCV allows internal engine pressure relief dumping into the air cleaner, and valve cover vents allow piston ring blow by to be vented without blowing valve cover gaskets. Am I close so far? Now that the engine is all nice and clean and back in the Jeep, do I hook it up as it was, hook it up as I understand it to be, or hook it up correctly? LOL. Allow me to muddy the waters a bit by adding the fact that the engine was incredibly clean inside when I opened it up. No sludge ANYWHERE. No sign of it at all, even in the bottom of the oil pan. Correct or not, the routing was working.

During the intake cleaning, I removed the freeze plug from the PCV port and added a grommet with the intent of putting the PCV valve in its correct place, but now I'm questioning the smarts in that. Here is the motor just before I pulled it -

Here is the PCV routing as I got it:

Here come the questions:

1. Even though the engine was sludge free, the PCV routing as I got is was incorrect, yes? PCV valve should be vertical...

2. Am I correct I'm believing the oil fill cap vent lets air into the engine, and the PCV valve should live at the rear of the intake (marked B) as shown in the following pic?

Pretty sure A is the water temp sensor location.....

3. C should be the vacuum port to which the brake booster and PCV should be connected? I did find some disagreement over whether the brake should be on it's own dedicated port or share a port with the PCV.

4. Now for the big one - I have factory valve covers, and neither they nor the nasty chromes one on the engine when I got it are/were ported for vents. Knowing my engine has some miles on it, and assuming I will have some blow by, wouldn't venting the valve covers be a wise idea? Wouldn't that help keep the valve cover gaskets from leaking? I wouldn't think it possible the PCV valve would allow pressure in the heads to vent.

My gut says to add valve cover venting, run the brake booster vacuum and PCV to the intake vacuum port just behind the carb, and filter the oil cap opening.

How close is that???? Lemme know where my logic is flawed, and don't hold back - can't hurt my feelings...... been married 29 years - don't have feelings anymore LMAO.

 

[Belizean]

LOL. No feelings. Sounds like a few psychic battles there . Surviving is half the battle. Sorry I won't be any help here

 

[shum8]

I’m kidding - that was always a favorite dating of an old friend..... I honor him by throwing it around. Those that know me know I’m kidding.........


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[PistolDave]

I may not be understanding exactly what you have going here. My 401 with Edelbrock intake had the PCV port in the rear of the intake manifold, and the valve covers were both sealed. I used a vented cap on the oil filler tube as you described. I ran a hose from the port on the filler cap to one of those old ford PCV breather filters that mounts just inside the air cleaner. That way the air that flows into the oil filler tube is passing thru the filter first. There was also a stamped metal splash shield that mounted to the underside of the intake where the PCV hole was, i'm assuming this was to keep oil from sloshing up onto the PCV.

Dave

 

[shum8]

The pics I posted were as it was when I pulled the engine. The oil cap vent ran to intake vacuum with a PCV valve inline. While that’s not the way it’s supposed to run, it must have worked. I plan on filtering the air going into the oil filler cap, and running the PCV valve in its correct spot. Guess I was mainly wanting to know if I needed to vent the valve covers or not.


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[mdeluca]

I enjoyed looking at your photos...

 

[Bjasper]

Not sure on this one you said you put a grommet in a vacuum port on the intake . I would put the pcv valve in that grommet .Then cut a hole in one of the valve covers to put another grommet in with a tube fitting choose a spot to clear the rocker arms Then connect a hose between the too .So the pcv will pull fumes from the crank case and the oil filler cap will let air in . They usually have filering media in them for that purpose if not buy a filtered breather cap

 

[shum8]

Not sure on this one you said you put a grommet in a vacuum port on the intake . I would put the pcv valve in that grommet .Then cut a hole in one of the valve covers to put another grommet in with a tube fitting choose a spot to clear the rocker arms Then connect a hose between the too .So the pcv will pull fumes from the crank case and the oil filler cap will let air in.

I have the PCV valve in the grommets hole in the rear of the intake and it runs to the vacuum port at the base of the carb. The oil filler cap will be filtered for air intake. You’re saying to vent one of the valve covers..... why not both? Seems to me they should either both be vented or neither......


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[Bjasper]

First off is the hole in the intake in a vacuum port or does in inter in to crank case ? Any way the goal is to evacuate blowby fumes and not build up pressure in the crank case as long as the pcv can pull fumes even from one valve cover the hole case relieved .It wouldn't hurt anything to do both valve covers .You do want make sure that the air drawn in is filtered

 

[Bjasper]

Sorry I get it now your pcv is in the intake exposed to case fumes and a hose to vacuum port .You should be fine the filler cap let's filtered air in to replace what the pcv draws out . My bad I need read closer for running my mouth

 

[shum8]

Here’s the port to which I added the grommet and PCV valve:

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[Bjasper]

I went out in my shop I have 1977 f250 with a 400 and performer intake.Sure enough I put my pcv in the same hole in the back of the intake that you are using .The only difference is my oil filler cap is in my valve cover and it filters the air going into block .If you think about it piston blow by ends up down around the crank and migrates up through liftter valley and that's open to the heads via push rods and oil drain back .Someone else mentioned running a hose from filler cap to inside air breather that's the very best arangment for clean incoming air

 

[shum8]

For some reason, all this time I’ve been thinking piston ring blow by heading for the valve cover - but that’s just dumb. If it’s going anywhere it’s down into the block - as soon as I read your post I thought “I’m an idiot”..... LOL As long as the block pressure is vented, shouldn’t be any in the heads......


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[Bjasper]

I remember when you would see a rubber hose that ran down the block from the intake no pcv back then after the motor heated up you would be smokey vopor streaming out of the hose .I miss the good old days when the emission system was one rubber hose LOL

 

[mtnwhlr]

Yea it was a hose that came out the bottom and would have smoke coming out of it. Ahh the good old days.