Question: Oil Filler Neck ventilation tube

Im not sure, but Ive got a similar setup, so ill give you a bump.

That hose is bi-directional --- when the intake is under vacuum (idle, deceleration, cruise speeds) it tries to pull a vacuum on the crankcase through the pcv valve. To prevent a vacuum from being pulled on the crankcase, a source of metered make up air (air that's passed through the maf) must be provided. That's what the hose between the throttle body and the valve cover oil filler neck nipple is for - it allows metered air to flow FROM the throttle body INTO the crankcase. Conversely, when vacuum is NOT present in the intake (wide open throttle), the hose helps to vent crankcase pressure in the event the pcv hose isn't able to provide sufficient ventilation capacity. In this situation, air flows FROM the crankcase (via valve cover) INTO the throttle body.

The potential risks of not having it hooked up are three fold. 1) It allows unmetered air to enter the engine under vacuum conditions - this presents drivability problems for some cars. 2) At wide open throttle, there may not be enough capacity to vent the crankcase sufficiently which can allow crankcase pressure to build -- results can include popping the pcv valve out, popping the dipstick out, blowing excess oil into the intake, oil leaks out the valve cover gaskets and/or front/rear main seals. 3) It can allow a vacuum to be pulled on the crankcase which can also damage gaskets and seals -- people on a long cruises often complain of high pitched 'whistling' when they stop the car -- the sound of air squeezing past front/rear main seals trying to get INTO the crankcase.

Bronco_Guy said:

Hi,

First post here, but long time viewer. Last winter, I swapped my stock top end for the stuff in my sig. The information I collected off of this forum was invaluable, I couldn't have pulled this project off by myself without the knowledge of the posters here. Thank you.

At any rate, I really didn't pay much attention to the consequences of not attaching the hose running from the oil filler neck back to what I seem to remember was the throttle body or egr spacer. Since the new setup didn't seem to have a provision for that hose, I simply capped the nipple on the filler neck off and went on, still using my stock valve covers.

Do you guys think this is a bad, bad idea? If so, what would you suggest be done to address this?

Thanks, again!

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Listen to Micheal Yount, he knows what he's talking about. If you don't have a provision for the tube on the oil filler run a cap like this.

http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=482

Good luck.
Tim

....or you can drill a hole in the valve cover, and in the tubing/piping just upstream of the throttle body - go to your local hardware store and buy a couple of 5/16" or 3/8" barbed brass fittings that have threads on the other end. Install them in the drilled holes with a nut on the back side (use some loctite), and slip a length of the right size hose over the barbs. If you'd like it be less noticeable, use the back part of the valve cover (behind the throttle body) and the back side of the t/b inlet piping.

Sorry to hijack the thread, even though your question has been answered, but....What if i dont have the PVC plugged in? What are the pros/cons of it?

Scorcher2005 said:

What if i dont have the PVC plugged in? What are the pros/cons of it?

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The semi corrosive vapors inside of your crank case aren't evacuated and it shortens engine life. I don't see any pros of not running a PCV on an engine designed for a closed crankcase.

Even though it's not plugged in --- do you have the crankcase vented in some other fashion?

i have the vent/vaccum tube from the breather to the TB. I have the PVC just dangling as its not long enough to reach the lower intake, especially w/ the 1" spacer

If the pcv is hooked to the manifold with the tubing, but isn't sealed in the grommet, then you have one helluva vacuum leak.