PCV... to be or not to be

[Kit Sullivan]

A couple of points I'd like to make:

While PCV valves can last a long time if kept clean, they most certainly CAN wear out. The spring prrssure is prescribed to specific engines to alliw a specificamount of vacuum through the system: too much flow and you actually suck oil out of the engine...too little flow and and you don't ventilate the crankcase selk enough. While a worn-out valve technically can cause an oil consumption issue, it almost never happens that way. Usually they get gummed up and dirty, restricting flow and leading to a sludgy motor.

Most of our applications are available from any parts store.

Oily, foamy residue around a breather is typically a sign of worn valve guides.

If you are fanatical ( like me!) Install a water-trap on your PCV vacuum line and you will trap most of the worst oily, moisture-loaded goop in the cup before it has a chance to get back into your intake system. Just dump it out and clean evdry so often.

I installed one on my 2012 F150 when it was brand new and it catches a pretty good amount of crap and moisture. I run synthetic oil, change every 4-5000 miles. Oil is like new all the time.

My stock 429 was treated much the same for many years: nothing but synthetic oil from the first oil change ( in July of '74) and changed every 3-5000 miles.

At 325,000 miles the engine ran as good ( maybe better?) than new. No ticking, smoking, or any issues. It looked new inside when we took it apart.

 

[droptop73]

Hey guys, I'm not trying to be argumentative here. I did not just do the dual valves without thinking it through. I completely understand the theory of the PCV to VENTILATE the crankcase. When you have an open vent on one side and a port connected to manifold vacuum on the other end there is no vacuum created, only flow. Vacuum requires a restriction which there is not much of one on the original system with a 1/2" hose on the inlet and a 5/16" tube in the carb/manifold end. Proper crankcase pressure (negative) is critical for oil control. If you look at modern cars, even going back into the late 70s there is a sealed cap on one cover and a PCV on the other. Most high end race engines today actually have external vacuum pumps to create negative crankcase pressure. This technique reduces windage in the crankcase along with reducing internal pressure (wind resistance) against the piston's movement, believe it or don't, its worth measurable horsepower.

So... that's the theory behind what I'm trying. So far, afrer a few thousand miles, there is MUCH less oil mess on the valve covers and no appreciable oil consumption. BTW, I'm very open to discussion on this experiment. I just wanted to explain how I got to this point. There's not much I do by accident.

 

[MechEng]

I have to agree with droptop73 on his theory. My 2012 mustang had both valve covers vented to negative pressure through the intake and it was designed for that.

Also the race car that I worked on had both valve covers sealed and a vent on the front of the timing cover that pulled negative vacuum with a small pump.

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[Jeff73Mach1]

Vacuum pumps pull all the time and generally in direct proportion to engine speed.

Manifold vacuum pulls in relation to load and rpm (or rpm and throttle position if you prefer)

I would be fearful of using a 2 PCV valve set up as our engines have no vent sources except the front and rear main seals, the dipstick seal

and the cylinders ring seal. I believe a different ring design and a series of check valves are designed into some of the systems you are using as an example.

You may be correct in your theory, but the way it is generally done is safe-your way is under testing-

But that is just my take on things.

 

[droptop73]

True, however, even small engines use a reed valve to create crankcase vacuum. Like I said it's an experiment, although unscientific.

Do I need a disclaimer? LOL

 

[Jeff73Mach1]

OK - so which PCV should be used? The Fram FV111 (I believe) is no longer offered through my local parts stores (even though they spec'd that unit). Not to mention, the Fram unit doesn't have the 'elbow' on top... it comes out straight up.

I have an Edelbrock breather on the driver side, and a Mr. Gasket breather with a hose outlet - is there an 'inline' PCV that could be used (cut the hose and place inline)? I'd love to keep the Mr. Gasket cap on there and still have proper PCV control.

Oldsmobile used an inline PCV valve

Look inside the PVC if you can, you'll see a number which correlates to the opening vacuum level. If you can match that number to a stock application's number you should be able to use it.

 

[TommyK]

Some interesting PCV valves and tech info here:

http://mewagner.com/?page_id=444

 

[Jeff73Mach1]

130 bucks for a PCV valve? Wow.

 

[Mesozoic]

Late model 302s, aka 5.0 HO EFI engines have a good PCV setup. I've seen very few of the late model 302s leak oil and their valvecover gaskets are pretty awesome too (they all use a steel frame with integral rubber gasket).

All use a sealed driver side valvecover (no breather at all). The PCV is installed in the back of the intake manifold within a recess opening up to the lifter valley, connecting to the intake manifold tract for suction. The passenger side valvecover has the oil fill cap with a nipple that is then connected to the throttle body/air intake some place after the MAF sensor so the computer knows how much additional air was used by the PCV system.

It's a good setup and one that I try to mimic on all of my engine builds. On my 351W I had to use both valvecovers, one plumbed to the fresh air inlet after the MAF and the other connected to the PCV (since the intake has no provision for the PCV). The 400M (Cleveland, basically) is similar. One valvecover with PCV going to the intake manifold for suction and the other valvecover has a tube connected to the fresh air inlet. No leaks!

 

[Jeff73Mach1]

I'm experimenting with the following setup Breather cap has been fitted with a pressure relief valve that opens under less than 3 pounds air pressure

Other valve cover has the PCV valve in a tall baffled cap and runs to my carb's 3/8th vacuum barb.

I drove over a hundred miles with this set up this weekend while breaking in my rings and making some minor adjustments. It worked beautifully. I fitted another cap up to hook to my vacuum gauge and it showed no signs of crankcase pressurization at idle or on no load revving of the engine.

 

[Mesozoic]

I'm experimenting with the following setup Breather cap has been fitted with a pressure relief valve that opens under less than 3 pounds air pressure

Other valve cover has the PCV valve in a tall baffled cap and runs to my carb's 3/8th vacuum barb.

I drove over a hundred miles with this set up this weekend while breaking in my rings and making some minor adjustments. It worked beautifully. I fitted another cap up to hook to my vacuum gauge and it showed no signs of crankcase pressurization at idle or on no load revving of the engine.

That sounds fine, just make sure that the breather with the pressure relief valve is inflowing fresh air. You'll sometimes see the fresh air inlet plumbed directly into the air cleaner on carb'd setups, often a small port on the throttle body or air intake elbow before the throttle body on EFI setups.

 

[mustang7173]

All,

Has anyone purchased this PVC?

http://mewagner.com/?p=444

 

[boilermaster]

All,

Has anyone purchased this PVC?

http://mewagner.com/?p=444

Mustang7173,

I have purchased and tuned this pcv for my 408 stroker.

Here are my thoughts:

if you have a stock engine run a stock pcv.

Never run un baffled rocker covers.

always use a pcv return hose.

We will often spend ungodly amounts of hard earned money on our engines 

why compromise on something so important ?

boilermaster

 

[mustang7173]

All,

Has anyone purchased this PVC?

http://mewagner.com/?p=444

Mustang7173,

I have purchased and tuned this pcv for my 408 stroker.

Here are my thoughts:

if you have a stock engine run a stock pcv.

Never run un baffled rocker covers.

always use a pcv return hose.

We will often spend ungodly amounts of hard earned money on our engines 

why compromise on something so important ?

boilermaster

Hello boilermaster ,

My 1994 302 roller is not stock. It has a nice Howard cam. I believe it may be just above the 303 cam. Not sure of the specs. due to engine builder threw out paper work. My FiTech EFI 400 has this up and down idle issue. I was working with adding trans. fluid and bumped my stock PVC valve. I re-orientated and pushed it down and notice that up and down idle stopped. Like, whoa, is this a possible problem? When I moved it again, it started back.

Here is the current PVC I have.



I do not want to go back to this type. I believe the M/E Wagner may solve my problem.

 

[boilermaster]

mustang7173,

Very satisfied with my MEwagner pcv valve, I did have to re tune it from my 351 to 408 swap.

The 351'' pulled 17.5'' at hot idle and the 408'' will ONLY pull 17''

the 408 will idle @ 800 rpms.

Boilermaster

 

[mustang7173]

mustang7173,

Very satisfied with my MEwagner pcv valve, I did have to re tune it from my 351 to 408 swap.

The 351'' pulled 17.5'' at hot idle and the 408'' will ONLY pull 17''

the 408 will idle @ 800 rpms.

Boilermaster

Boilermaster,

Got one on order. I will respond with end results. Thanks for your help!

 

[tony-muscle]

mustang7173,

Very satisfied with my MEwagner pcv valve, I did have to re tune it from my 351 to 408 swap.

The 351'' pulled 17.5'' at hot idle and the 408'' will ONLY pull 17''

the 408 will idle @ 800 rpms.

Boilermaster

Are you saying that the valve has to be retuned? How do you tune the valve? As you know i am stroking mine to 408. I have not purchased the PCV valve yet but this thread just reminded me.
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[boilermaster]

mustang7173,

Very satisfied with my MEwagner pcv valve, I did have to re tune it from my 351 to 408 swap.

The 351'' pulled 17.5'' at hot idle and the 408'' will ONLY pull 17''

the 408 will idle @ 800 rpms.

Boilermaster

Are you saying that the valve has to be retuned? How do you tune the valve? As you know i am stroking mine to 408. I have not purchased the PCV valve yet but this thread just reminded me.

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Tony muscle, the instructions are listed under technical on the site that mustang7173 posted.

I had originally installed the valve on my 351 c then put it on my 408 c stroker.

One suggestion:

set carb idle mixture to the best of your ability (warm) then adjust your new mewagner valve per instructions:

then go back and do carb idle mixture again, you MAY gain some vacuum.

Then go back and look at the instructions again, did you increase the vacuum enough to get to the next higher calibration ?

What we are actually doing here is picking the correct orifice size per cubic inch displacement and

vacuum readings.

Boilermaster

My 408C-4V is coming back from the shop soon. I will be receiving all the pieces and assembling it all.

The rotating assembly and internals are coming from TMeyer, which is work in progress as we speak. More information on these to come.

I am not completely decided on some of the peripherals so this thread is to seek opinions.

Edit:

As an idea, the goal of the build is to be a ~475-500 HP engine with factory 4V valves. It will be topped off with a BlueThunder manifold and the FiTech EFI. I am using Hooker Comp headers. All these were in my 351C. The valve train would be hydraulic roller with the camshaft to be decided.

 

[EdM]

I have one on my mild Cleveland build and really like it. The motor idled better and minor oil around the valve cover grommets went away. I am doing a 427 Windsor swap very soon (motor is built) and will use it again, tuned as necessary.