correct pcv for explorer 5.0 non efi

[Hinmaton]

Title says it- Can anyone point me towards the correct pcv for valve cover installation on a 95 Explorer 5.0 not running Ford EFI? I'm going to route a catch can from it to manifold vacuum.


Hinmaton

 

[duffymahoney]

Why not route the pcv to the air filter or intake? Positive venting is always better then a catch can. Are you running a carb?

 

[DirtDonk]

I think the catch-can is likely to be in the vacuum side to keep oil out of the intake in case the baffling is not up to snuff.

With a regular carb intake, you will have to put the valve in the valve cover as you were saying. If you have proper valve covers (hopefully with decent baffles) you want the valve in one cover (does not matter which side so go with whatever is most convenient or gives the cleanest tube routing). Choosing the correct valve may involve a little more discussion.
Your vacuum source must be a common one. Either into the intake manifold common plenum area, or to the base of the carburetor itself. Never into one single intake runner. That location is for power brakes and such, but never PCV.
Fittings are usually the larger 3/8" size.

What kind of air cleaner housing will you be using? You want clean air going back into the opposite valve cover, so this is as critical a decision as the valve side.
Most valve covers either come with, or have the option to buy a filtered breather to go into the hole. This is adequate, but often leads to an oily mess after awhile. But lots of them in use, so it's not the end of the world.
If you go with an elbow and hose to the air filter housing, it has to be on the inside (filtered side) of the housing so that only clean air enters the engine.

That's basically it. A PCV system is very simple on a carbureted engine. One side gets suckage from vacuum, the other side is sucking air in, so needs to be filtered. Done.

Paul

 

[Hinmaton]

Why not route the pcv to the air filter or intake? Positive venting is always better then a catch can. Are you running a carb?

Running TBI and that is how I had it running. All the oil pushes out of my cone air filter.


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[duffymahoney]

You could also drop to a catch can, then vent the catch can to the intake. Stock style air filter or?

 

[Teal68]

Not sure if this is proper or not, but I pulled the PVC from the EFI system and stuck it in the rocker cover. I have done 3 carb'd explorer engines to date this way with no issues.

 

[Hinmaton]

Not sure if this is proper or not, but I pulled the PVC from the EFI system and stuck it in the rocker cover. I have done 3 carb'd explorer engines to date this way with no issues.

Oh. Okay that could work.


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[Hinmaton]

Does anyone know if just any PCV will work? I recall reading that each engine was designed for different ventilation pressures or something, so you need the right one for your style of motor.
Any truth to that?


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[Broncobowsher]

There is some difference in PCV valves. I just pick one for a small block Ford and it works fine. If I were running a big block or a little 4-cylinder I would get one matched to that general engine.

 

[DirtDonk]

I look to how to plumb it the cleanest way as to whether I go with the stock Explorer valve (straight up tip) or one from another model (90° elbow) because I like to route hoses and custom bent tubing in different ways in different engine compartments.
Stick with at least a valve from a medium performance engine. The one I got that fit the physical bill but that was obviously wrong from the first start-up was one from a '74 Monarch/Grenada with 302. Ran super lean and did not like that valve.
At the time the solution for me was one from a '72 Corvette w/350. But plenty of Ford engines have the 90 degree fittings and would be just as appropriate.

If you're building a custom engine and don't mind spending $150 for the last PCV valve you'll ever need, there is a custom "tunable" PCV valve offered through the aftermarket that is extremely cool. A couple of members here are using them.
Pretty much overkill for most casual builders with mild engines, but if you experiment with different cams and inductions from mild to wild, it's clearly a winner.

Paul

 

[Hinmaton]

I look to how to plumb it the cleanest way as to whether I go with the stock Explorer valve (straight up tip) or one from another model (90° elbow) because I like to route hoses and custom bent tubing in different ways in different engine compartments.
Stick with at least a valve from a medium performance engine. The one I got that fit the physical bill but that was obviously wrong from the first start-up was one from a '74 Monarch/Grenada with 302. Ran super lean and did not like that valve.
At the time the solution for me was one from a '72 Corvette w/350. But plenty of Ford engines have the 90 degree fittings and would be just as appropriate.

If you're building a custom engine and don't mind spending $150 for the last PCV valve you'll ever need, there is a custom "tunable" PCV valve offered through the aftermarket that is extremely cool. A couple of members here are using them.
Pretty much overkill for most casual builders with mild engines, but if you experiment with different cams and inductions from mild to wild, it's clearly a winner.

Paul

Thanks Paul.
Good point on the straight vs 90. I guess for me it’ll be the difference between either running to the air cleaner or to the manifold. My understanding is it’s better to go below the butterflies. Is this true?

Hh


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[DirtDonk]

That’s not really a choice because what I think you’re describing are the two separate halves of the PCV system.
The clean air return always goes to the air filter so that clean air gets back into the engine. The valve itself always goes to full manifold vacuum under the butterflies in a common area.
Never from a single intake runner.

You can run a vacuum booster for your brakes or other accessories from a single intake runner, but a PCV system has to run to a common plenum area.

 

[Hinmaton]

That’s not really a choice because what I think you’re describing are the two separate halves of the PCV system.
The clean air return always goes to the air filter so that clean air gets back into the engine. The valve itself always goes to full manifold vacuum under the butterflies in a common area.
Never from a single intake runner.

You can run a vacuum booster for your brakes or other accessories from a single intake runner, but a PCV system has to run to a common plenum area.

What is this clean air return you speak of? Where does the clean air come from? What am I missing?

Hh


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[duffymahoney]

What is this clean air return you speak of? Where does the clean air come from? What am I missing?

Hh


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PCV sucks clean air in one side and dirty air into the intake. Picture of your setup?

 

[DirtDonk]

What duffy said. It’s a closed loop system for lack of a better term. They are not all truly closed, since some of them can simply use a filtered cap, but the idea is that vacuum from the intake sucks out the acidic gases and excess moisture from inside the engine.
But to do so you have to have air coming back in and it wouldn’t be very good to suck in dirty air so it has to be filtered.

If you were just sucking with vacuum you would be creating a vacuum inside the engine (which in itself is not a bad thing) but that’s not very efficient at pulling gases out because there’s no actual flow, or cycle. Not until you have a way for air to come back in do you get that “positive” flow.

If you look at any system the vacuum is a controlled vacuum leak essentially with the PCV valve controlling the timing and amount.
Usually somewhere on the other side of an engine is an opening with a tube going to the factory air filter housing.
Aftermarket valve covers off come with a filtered cap to pop over the open port.

 

[jamesroney]

That’s not really a choice because what I think you’re describing are the two separate halves of the PCV system.
The clean air return always goes to the air filter so that clean air gets back into the engine. The valve itself always goes to full manifold vacuum under the butterflies in a common area.
Never from a single intake runner.

You can run a vacuum booster for your brakes or other accessories from a single intake runner, but a PCV system has to run to a common plenum area.

I'm always amused by how many people get this wrong. Even Shelby got it wrong. The black and white picture below is from the 1967 magazine road test. The color pic shows better detail. You can see that the PCV valve is connected to the filtered side of the air cleaner. LH Breather is not ported to anything.

Totally wrong, and totally outside the design envelope. But sort of effective, and better than a road draft tube.

Don't do this!

 

[Hinmaton]

I'm always amused by how many people get this wrong. Even Shelby got it wrong. The black and white picture below is from the 1967 magazine road test. The color pic shows better detail. You can see that the PCV valve is connected to the filtered side of the air cleaner. LH Breather is not ported to anything.

Totally wrong, and totally outside the design envelope. But sort of effective, and better than a road draft tube.

Don't do this!

Yeah, this is essentially what I inherited on my engine, but without a pcv, just a draught tube plumbed to the air cleaner.


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[Hinmaton]

I can’t provide a photo as I really don’t have a system. That’s the problem.
The motor is a 95 or so Explorer motor that has been swapped to a 2 barrel carb. I put the throttle body efi on, but didn’t know what to do with the crankcase ventilation.
The valve covers had one baffled port attached to the oil fill, and nothing on the other side. I punched in a breather, but the crankcase just pushes oil out breather. So I vented it to the cleaner and it pushes oil out the filter.
I thought the pcv simply ran from the valve cover to the manifold. No?

But the Explorer ran from the valve cover nipple to the back of the manifold with the pcv in the manifold, right?

So is the second tube the “clean air”?

I thought crank case ventilation was the controlled release of pressure built up by small bits of blow by built up over time? Why would you need fresh air adding to that?

Hh


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[DirtDonk]

No. The two pictures show two different set ups. The one in the valve cover is common for the 351/5.8 size engines, while the one in the back of the intake manifold is common for the 302/5.0.

The second picture would have been correct for the explorer, but you are only seeing one half of the system.
You see the valve in the lower intake and both hoses are full vacuum from ports on the underside of the upper intake. The main (only?) reason for two of them is to give the oil vapors a chance to condense in different parts of the intake manifold so that no one section collects too much liquid oil.
The explorer lower already had one of the best baffle systems in the business, but that doesn’t mean you won’t still condense in the upper. So spreading it out was a good thing.

The little tube fitting in the oil fill neck of the passenger side valve cover gets a simple hose connected between it and the throttlebody when you are still using ford EFI.
Because you no longer have a Ford throttlebody you connect the hose from the valve cover to the filtered section of your existing air filter housing.

Two separate halves of one system. You have full vacuum connected to the PCV valve, and you have fresh filtered air connected to the valve cover.

 

[Hinmaton]

No. The two pictures show two different set ups. The one in the valve cover is common for the 351/5.8 size engines, while the one in the back of the intake manifold is common for the 302/5.0.

The second picture would have been correct for the explorer, but you are only seeing one half of the system.
You see the valve in the lower intake and both hoses are full vacuum from ports on the underside of the upper intake. The main (only?) reason for two of them is to give the oil vapors a chance to condense in different parts of the intake manifold so that no one section collects too much liquid oil.
The explorer lower already had one of the best baffle systems in the business, but that doesn’t mean you won’t still condense in the upper. So spreading it out was a good thing.

The little tube fitting in the oil fill neck of the passenger side valve cover gets a simple hose connected between it and the throttlebody when you are still using ford EFI.
Because you no longer have a throttlebody you connect the hose from the valve cover to the filtered section of your existing air filter housing.

Two separate halves of one system. You have full vacuum connected to the PCV valve, and you have fresh filtered air connected to the valve cover.

Okay- that’s what I was missing. Got it.

Hh


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