Pcv valve troubles

[Mbosse]

So I have a 383 I’m about to put in my 98. I bought it with valve covers that have two breathers on one side and nothing on the other. I plan on adding a hole for my Pcv on the drivers side where nothing is at and probably a catch can before the intake. What I’m curious about is if I should leave the two breathers on the one side or if I should go back to stock with the breather for the crankcase coming from the air intake. I’m completely lost in forums trying to figure out which is better. It would be a lot easier to just use the breathers on the engine right now but if it’s better for the air to come from the intake I’ll do it.

 

[GoToGuy]

The crankcase ventilation, intake vacuum pulls excess or fumes from engine internal through PCV, ( positive crankcase ventilation) . Not from , routed to intake manifold . Vacuum at intake manifold. Changes in vacuum pressure regulates how the PVC valve functions to reuse case blowby.
Use one valve cover port for pvc valve to intake as designed. Use the other as oil fill or seal it. Just don't vent to atmosphere. All the crankcase vapor, blowby is meant to be returned to combustion cycle.

 

[454cid]

Assuming fuel injection, I'd want to pull filtered air after the MAF, so your not adding extra air that the efi doesn't know about.

 

[GoToGuy]

What filtered air? It's PCV . Look at the hose routing.

 

[Pinger]

Assuming fuel injection, I'd want to pull filtered air after the MAF, so your not adding extra air that the efi doesn't know about.

The above. Filtered and metered.

 

[Mbosse]

Assuming fuel injection, I'd want to pull filtered air after the MAF, so your not adding extra air that the efi doesn't know about.

Yeah but wouldn’t it actually be better since the engine wouldn’t be pulling air from the metered air through to the other side. Dosent it work like a circle coming in one side and venting to the other side making a circle.

 

[Schurkey]

I bought it with valve covers that have two breathers on one side and nothing on the other. I plan on adding a hole for my Pcv on the drivers side where nothing is at and probably a catch can before the intake. What I’m curious about is if I should leave the two breathers on the one side or if I should go back to stock with the breather for the crankcase coming from the air intake.

The OEM PCV system has been "closed" for decades. The first half-dozen years of PCV systems were "open". The difference is that the open systems used a breather that vented to atmosphere, the closed systems vent into the clean side of the air filter, or had a separate air filter in the air cleaner housing.

Point is, air gets filtered before it enters the crankcase, picks up fumes and moisture, and is then evacuated into the fuel/air stream in the intake manifold.

Under normal circumstances, that's the flow path--clean air from the air cleaner area, into the crankcase, into the intake manifold via the PCV valve.

But what if there's too much blowby for the PCV system to evacuate? In that case, the open system vents those fumes to atmosphere, which is EEEEEEeeeeevil. The closed system vents those fumes into the air cleaner--which is then drawn into the throttle body and then into the intake manifold bypassing the PCV valve. Either way...the fumes are drawn into the intake manifold and re-burned.

Therefore, you need a PCV valve and plumbing into the intake manifold, arranged so that the fumes are likely to be distributed evenly among all the cylinders. On the other valve cover, you need plumbing allowing fresh, filtered air INTO the crankcase. (And allowing excess crankcase fumes into the intake tract under heavy throttle or when the engine is worn-out.)

What filtered air? It's PCV . Look at the hose routing.

The fresh air that enters the crankcase has to be filtered. As said--sometimes by the regular air filter, sometimes by a smaller PCV filter located inside the air cleaner.

Look in the service manual to see where the fresh air is sourced--after the MAF seems very likely. And that will also show you where the PCV plumbing is connected at the manifold, so it's distributed evenly.

 

[tpass]

remember the old "draft tubes" of the 50's and 60's..... crankcases would vent thru a tube to the bottom of the car, directly on the roadway. And why it used to be REALLY dodgy driving during the first rain after a dry spell. all the roads had oil stains down the middle of the lanes.

 

[GoToGuy]

The 409 I got out of wrecking Yard for my 55 GMC had this nice black tube , like an extra exhaust pipe. LOL.

 

[Schurkey]

remember the old "draft tubes" of the 50's and 60's..... crankcases would vent thru a tube to the bottom of the car, directly on the roadway. And why it used to be REALLY dodgy driving during the first rain after a dry spell. all the roads had oil stains down the middle of the lanes.

The 409 I got out of wrecking Yard for my 55 GMC had this nice black tube , like an extra exhaust pipe. LOL.

That oil stain "slime" is visible in several sections of this video. Where the road is clean...the pavement is new. And there's a lot of new and new-ish pavement in the video. Check out the highway at 2:31.

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