Breathers and PCV

Here's a photo of the stock vs. Billet Specialties PCV and the proposed Holley carb connection:

There are a number of ways to connect the PCV to the engine but the simplest way is to drill & tap the intake manifold plenum in a convenient place for a pipe thread, and use the proper sized hose barb to match the PCV spigot you have. Or, make up a Tee fitting and connect the PCV to the existing 1/2" vacuum hose to the power brakes with a short connector. This is how our engine has been rigged for decades.

The stock Cleveland valve cover caps fit those valve covers just fine. The caps use a PCV valve on one cap and a vent line to the air cleaner on the other cap. Like always all the details are here just a click away http://www.panteraplace.com/page226.htm

Mike

Dennis,

Whether or not the Billet Specialties PCV or any PCV valve will operate in your motor depends upon how much intake manifold vacuum you have at idle. You need enough vacuum to "suck" the valve closed. It easy enough to test, just start the motor, let it idle, pull the PCV valve out of the valve cover, turn it over and observe the valve plug. It should be closed tightly so that it can't suck air into the motor at idle

A good FYI, the Boss 302 PCV valve operates at a lower vacuum setting than the 351C PCV valve, it makes a good PCV to use in a performance motor.

The power brake booster can be connected to any connection on the intake manifold, it won't impact anything. The PCV needs to be connected to a fitting that will distribute the air drawn through the PCV system evenly as possible to every cylinder. The big fitting on the carburetor base is designed for that purpose.

Your motor looks really nice! Good job. Is that a Holley HP carb? What cam did you use? Did the engine builder dyno the motor? Do you have a peak BHP @ RPM reading?

-G

George,
Thanks for the advice on how to test the PCV. Since I really like the look of the billet breathers, I will do the test before I consider plan B.

Yes, the carb is a 750 4150 HP. You will note that I followed your advice on using CHI heads as well as the Scott Cook dual plane intake. CHI leveled the carb pad for me (well almost, they were able to get it to within 2 degrees from level). I'm still hoping to fit everything under the stock engine cover. I realize that CHI heads are now yesterday's news, but I feel that they are a great choice. The engine builder was really impressed with the CHI heads, but he was probably most impressed with how good the dual plane intake worked.

The egine was bored .020" over with an internally balanced 3.750" stroker, which equals 380 c.i. As you recommended, an ATI Super Damper was used. They used a Windsor timing gear to make the spacer for the crankshaft. We used a Comp Cam with solid roller lifters and roller rockers. The lift is .659 intake and .666 exhaust. Duration at .050 is 242 intake and 248 exhaust.

As for the dyno, I was able to witness pull #3. Running 93 octane, 10% ethanol pump gas with timing set a 30 degrees, the peak HP was 522 at 6600 rpms. It ran right up to 7000 rpms and wanted to keep on going. It was still making 519 HP at 7100 rpms, but also was making over 500 HP at 5700 rpms. Torque was pretty flat and peaked at 467 at 5500 rpms, but was making 450 at 3700 rpms. This was with no mufflers connected, but the headers used were smaller diameter than what I will be using. I will be using GTS headers and mufflers, so I realize I will sacrifice some of that horsepower to get the look and sound that I like.
Dennis

quote:

Originally posted by Cowboy from Hell:
Dennis,

Whether or not the Billet Specialties PCV or any PCV valve will operate in your motor depends upon how much intake manifold vacuum you have at idle. You need enough vacuum to "suck" the valve closed. It easy enough to test, just start the motor, let it idle, pull the PCV valve out of the valve cover, turn it over and observe the valve plug. It should be closed tightly so that it can't suck air into the motor at idle

-G

George,

I’ve reread this section a number of times but I still might be misunderstanding what you are describing.

Here is how I have it set up on my Pantera. At idle and deceleration, e.g. high vacuum, the valve is open with some regulated flow. Meaning if you look at the end of the valve you will see an opening and air can flow through it. When the engine is off the valve will be closed and during a back fire. So at a normal idle, the valve will be open and a regulated air flow is present. The air flow and regulation of the valve orifice changes depending on vacuum or air flow available.

In my case, filtered air from inside the air cleaner is flowing through the hose to the back right valve cover cap, through the cap, through the engine and up into the left valve cover, through the open PCV valve, into the intake manifold and into the combustion of the engine. Here is a link that has some helpful diagrams http://www.aa1car.com/library/pcv.htm

It is possible that you are describing the same thing and I’m just misreading it.

Mike

At idle, when the manifold is under high vacuum, the plug should be "sucked" inward into the body of the PCV valve. Like picture 1B.

The fuel air ratio curve of a motor is fish hook shaped, it is rich at idle, lean in the middle, and rich again at wide open throttle. The engine must be a little richer at idle in order to idle properly and not stall. If you let too much air into the engine at idle it will lean the mixture out, cause the motor to idle rough, possible stumble, and possibly stall. So although the plug is sucked deeply into the body of the PCV valve, the PCV valve is designed internally to either shut off air flow altogether, or to regulate it down to a small trickle.

The internal design of PCV valves vary, they sometimes have a mating face on the end of the plug you can't see, and the body of the PCV valve sometimes has a seat for that mating face to seal against. Observe the pic above.

(1) Is designed so it never completely shuts off (no internal seat, no mating face on the plug)
(2) Is designed to shut off but it allows a small regulated flow via a drilled orifice in the plug
(3 & 4) Are designed to shut off completely

I just read the emissions section of the '73 Ford Engine Manual and it says the PCV system is designed to operate full time when the motor is running. So you got me Mike, I'm "kinda" wrong. But the concept still holds true, if the PCV valve allows too much air flow at idle, the motor will idle rougher than it should. In that case the Boss 302 PCV valve is a known remedy.

Blow-by is at a minimum at idle, so shutting the PCV valve off entirely at idle is not a bad thing, unless you're a manufacturer trying to meet federal emissions regualtions.

Where the PCV system doesn't work properly is at wide open throttle. In that situation blow-by is at its maximum, yet intake manifold vacuum is so low that the PCV valve is almost in the engine-off position, it is not drawing much, if any, vapors from the crank case. The blow-by ends up blowing out the breathers. This is why race cars must use something other than a PCV valve to draw vapors from the motor (exhaust aspirators or vacuum pumps).

-G

Thanks for the explanation George. I know you “know your stuff” so knew it had to be the way it was written and not what you thought.

It is interesting how messed up Panteras can get from decades of shade tree mechanics wrenching on them so it is important that we know how to put systems back to the correct working order. This forum is a great resource for making that happen.

In the case of my car, when I bought It the PCV system had been disabled by installing a non-vented cap on the intake side of the system. Luckily the engine was not very old and it didn’t have time to be damaged by excess condensation, etc. Some of the stuff I’ve seen on Panteras in the last twelve years of being in the community sometimes amazes me.

What is odd, that in most cases doing it right would have been easer or just slightly more effort. Knowledge gap I guess!!

Mike

Its also entirely possible to install PCVs upside down in the grommet without a leak. I've seen this from experienced engine guys who get in a hurry. In that position you'll get smoke from the exhaust in left hand turns and reversed function from the PCV.