Hey all,

So, I have a stock intake manifold that I have been playing with for some time now. I have pulled the fittings for the BOV line and the FPR line out of the manifold mecause I do not use them. I drilled and plugged them with 1/8"npt block off fittings, as well as modifying the brake booster line. Now, I pulled the fitting for the PCV system as well. It's the 90* fitting that is at the end of the manifold, opposite of the throttle body, just above the 4th intake runner. I originally was going to put a 3/8"npt barb fitting to try and give it more clearance for the fuel rail and FPR (Perrin), but I am thinking of having it welded shut now.

So, I am assuming that the fitting that goes into the valve train cover, just behind and to the right of the oil cap has a check valve in it, to keep from boosting into the valve train cover. Is that small fitting (Comming out of the back of the valve train cover) really a check valve? And, if I have the port on the manifold welded shut, can I remove the fitting from the back of the valve train cover, and just put a breather filter onto it?

If I do have the port on the manifold welded shut, and remove the check valve, it would seem as though the port on the front drivers side that leads to the intake would draw air across the valve train cover, as the intake is always under vacuum. So, for simplicity sake, does this sound like something I can do that I will not run into problems later with? I am not doing this to try and gain power, I am just trying to eliminate useless crap while I have the spare manifold off the car.

Thanks for any help..

 

Sheesh, maye I should have asked if I can vent my BOV to Atmosphere, I would have surely got an answer then....


Morning Bump..

 

Bump..

 

Bump for the morning Monday workers who are already bored...

 

Bump for ya. Monday morning, working, and bored to tears

 

You will be fine. As long as you route the hoses coming off of the valve cover to an oil breather tank you will be good to go. There will be a small amount of metered air lost, but it shouldn't be enough to cause any problems. Hope this helps.

 

There is a check valve there, it's the PCV valve. Just like you thought, it allows the manifold to pull crankcase gasses out to be burned for emissions purposes as well as closed loop fuel control.

If you don't run a catch can, I wouldn't use a breather filter on it. Thread in a barbed fitting and run a hose from it, so you don't end up with oil residue all over the place. With the DSM valve covers the brake boost fitting would thread in, or a 1/8th BSP to hose barb (3/8th is typical) rom mcmaster. The right thing to do is run catch can to catch the oil, rather than just dump it on the street though.

 

Actually, yeah that help a lot. I think as long as I weld the port completely shut, I should be alright.

The only thing, after thinking of it on a really boring day at work, is the air that s being drawn across the valve train cover, with the nipple being post MAF, I would be introducing unmetered air into the system. I wonder if it would draw enough to really screw things up? Maybe in the breather filter I can put some sort of reducer pill, kind of like what is in the turbo lines to minimize the air draw, but yet keep enough comming in that it will prevent oil and crap from comming out of the filter...

Hmmm....

 

If you restrict that port, you'll also be restricting air that vents out under boost. That's bad. Most poeple add a second port to allow even more air to vent.

Venting the valve cover will certainly throw off your fuel trims, but it can be tuned out, if you have something to tune with. I remember it changing trims by as much as 6-10% at idle.

 

That's not what I mean. I probably didn't explain it like I was thinking.

I meant since the front side of the cover is pulling out of the valve cover and into the air intake, if the PCV wasn't hooked up, it was be sucking in air at that other port by the oil cap. If I was to put a breather on it, it would be constantly drawing in air because the intake side would always be under vacuum, thus drawing the air into the "opened" PCV fitting. If I was to put a breather filter onto the PCV fitting, instead of having it be a 3/8 open hole (The outlet size of the breather filter), I could put in a 3/8" dia. brass piece with say a 1/8" drilled hole in it, so that it created "more suction" due to the smaller size of the hole, to try and keep oil from blowing back out of the breather...

The more I am thinking about it, the more I am tempted to just leave well enough alone, and tap that hole for the 3/8" NPT to 3/8" hose barb I already bought for it.

Does anyone know what size the PCV thread is in the back of the valve train cover?

 

When you weld your hole shut on your intake, all the vaccum is gone. Even under idle your PCV valve is sucking its blowing out. Your crankcase should never have vaccum on it unless your running a vaccum pump. Weld your holes shut on your intake and plumb your breather lines to a catch can and you will be fine. You don't need a PCV valve when your not feeding it back to the intake.

 

Just make a new one out of 4130...chromoly, you know!?!?

 

May be a market in those.

 

Awesome dude, like, OMG, I never thought of that, like wow...


My god.....

 

You've managed to thoroughly confuse me now. There is no appreciable vacuum in the intake pipe. The only vacuum worth mentioning is from the intake manifold via the PCV valve. Once that is disconnected, there will be positive pressure in the crankcase pretty much 100% of the time. If I'm understanding you at all, you're talking about leaving the vent to the intake pipe hooked up and venting the PCV port, which would indeed be a bit unconventional. People usually do it the other way around, which porks trims since you still have a solid vacuum applied to the crankcase via the PCV valve and an open system with the intake port vented.

What poeple with high HP setups tend to do is to vent both the PCV and the Intake ports to atmosphere. Plug the hole in the intake pipe and in the intake manifold, and drive it on.

If none of this applies to your qestion still, you're on your own.