PCV setup

[jray]

Was reading on an earlier post about pcv setups. My 302 has a pcv valve on the rear of the passenger valve cover routed to the air breather. There is a vent (I actually thought it was another pcv) on the oil filler cap on the driver's side valve cover that is routed to a port on the bottom rear of the carb. Is this the way it should be, the earlier post on oil pressure sort of made it sound like mine was backwards, or does it really matter?

 

[rjlougee]

Sounds backwards to me. The fresh air should go to an elbow or vent in one valve cover, so fresh/clean air gets pulled into the engine there. On the other valve cover you should have the PCV, which should run up to the spacer under the carb.
Joe

 

[jray]

I won't be at home to investigate until tomorrow. I guess I should pull them off to see which one is the pcv and which one is the elbow (hopefully not another pcv). I don't guess it matters which way it is set up, just so long as one is fresh air in and the other is out to the carb?

 

[thegreatjustino]

PVC valve should be in the front hole on the driver side valve cover and hooked to the base of the carb.

 

[jray]

Hey, that's what I think I've got, thanks!

 

[barronj]

If only one of my valve covers has a port/nipple (and this is where I'm running my pcv to the carb), should i drill the other & run a line to vent the crankcase to the air cleaner?

 

[DirtDonk]

What kind of valve covers do you have? EFI style? Aftermarket that are supposed to be modified by the end-user? If so, that would explain why one does not have any hole.
Assuming you're running a carb, then yes, one cover would have the actual pcv valve plumbed to the carb/vacuum and the other would have either a nipple with a hose running to the air-filter housing, or a stand-alone filter element.
Either way, you're just trying to get clean air into the engine. The stand-alone filter element is convenient, but can end up being messy as vapor buildup turns to drool all over your valve cover.

And it doesn't matter which side the valve is or which side the filtered air goe in. Whatever is most convenient for plumbing purposes.

If you're runnin an EFI setup, the valve fits into the back of the intake manifold and the filtered air goes in one valve cover.

Paul

 

[DirtDonk]

I guess I should pull them off to see which one is the pcv and which one is the elbow (hopefully not another pcv). I don't guess it matters which way it is set up, just so long as one is fresh air in and the other is out to the carb?

Yep. Exactly right.
It's pretty easy to tell the difference just by looking. The "elbows" are usually at roughly a 45° angle and fit tightly into the rubber grommet right into the valve cover.
The PCV valve is a separate piece that (usually) can be popped right out of it's grommet in the filler cap. Most valves have either a straight hose fitting, or a full 90° nipple. Stock, at least for the earlier years, was straight.
I say "usually" because someone here just recently was having a heck of a time pulling his out of the grommet.

Paul

 

[barronj]

What kind of valve covers do you have? EFI style? Aftermarket that are supposed to be modified by the end-user? If so, that would explain why one does not have any hole.
Assuming you're running a carb, then yes, one cover would have the actual pcv valve plumbed to the carb/vacuum and the other would have either a nipple with a hose running to the air-filter housing, or a stand-alone filter element.
Either way, you're just trying to get clean air into the engine. The stand-alone filter element is convenient, but can end up being messy as vapor buildup turns to drool all over your valve cover.

And it doesn't matter which side the valve is or which side the filtered air goe in. Whatever is most convenient for plumbing purposes.

If you're runnin an EFI setup, the valve fits into the back of the intake manifold and the filtered air goes in one valve cover.

Paul

Thanks! Yes, I'm running the valve covers off a mustang for now.

 

[chuck]

The PCV valve must go to the vac. source and the vent must go to the clean side of the air cleaner. The PCV valve can be in the back of the back of the engine or in either valve cover and the fresh air/vent side can be in either valve cover. The idea is to suck the crankcase gases or combustion blowby out of the crankcase and into the combustion chamber then out the exhaust. If the crankcase has negitive pressure the clean, fresh air is drawn in.

 

[thunderbolt]

If you're not too worried about a factory look or emissions, I would just omit the pcv all together. It just feeds an oil mist into your intake manifold and intake ports whenever crankcase pressure goes positive at all. Not a huge deal, just makes a mess inside and oil doesn't make great power when mixed with your air and fuel. Otherwise, the above statements are correct.

 

[chuck]

I used to think the same but the PCV system Petty much eliminates sludge. Before the PCV system sludge was the main reason for engine failure.

 

[Viperwolf1]

It just feeds an oil mist into your intake manifold and intake ports whenever crankcase pressure goes positive at all.

Not true. The intake vac on the PCV valve creates ventilation of the crankcase gases whenever the vac is high. These gases include water vapor and gasoline fumes. When vac is low (full throttle) the ventilation is cutoff.

Your operational description is more like the old road draft tube ventilation that existed prior to PCV valves, except without the gases going into the intake.

 

[thunderbolt]

I'm sorry, for what it's worth, I got a little bit ahead of myself. My intention was to say if there was ever any kind of high crankcase pressure from excessive blow by at WOT, keeping the pressure much higher than manifold pressure. Hopefully it's mostly unspent combustion gases passing back into the manifold. But I don't want to jack this gentlemans thread, so I'll be quiet. Continue on, please...