Pressure in my valve cover!?

65 B/FX · May 8th, 2008, 10:12 PM

Anybody know why Id get a ton of pressure buildup at higher rpms in my Valve cover (PCV side)? Doesnt happen on the other side, and my PCV is new and check out ok. Could this be rings that arent sealing and at high revs the pressure gets too high? It blows out my valve cover gasket and you hear a "whistling sound" until it idles again. Gets some oil on my intake too. The other side has a breather and seams to be ok. Im stumped.

ryans88gt · May 9th, 2008, 12:08 AM

get a new breather

65 B/FX · May 9th, 2008, 12:40 AM

breather tests fine. Any other ideas?

ryans88gt · May 9th, 2008, 02:12 PM

If your breather works fine, then you have no pressure under the valve cover.

trueblue01 · May 9th, 2008, 04:46 PM

Crankcase and inside of valve covers (both sides) are in common atmosphere. Pressure is the same. Ring blow by comes out the bottom of the cylinder into the crankcase.

qwik48r · May 9th, 2008, 04:52 PM

sounds like valve blow by.... take a compression reading of the problem bank.

ryans88gt · May 9th, 2008, 05:53 PM

IF you had enough blow by, either from rings or valve seals, that a valve cover breather wasn't enough to vent (figure more than 200 cfm), then you would have more serious problems than a leaking valve cover gasket. Like burning 2 quarts of oil a day.

ryans88gt · May 9th, 2008, 05:55 PM

Originally Posted by trueblue01

Crankcase and inside of valve covers (both sides) are in common atmosphere. Pressure is the same. Ring blow by comes out the bottom of the cylinder into the crankcase.

In this case, he has breathers and a PCV, so everything should be at atmospheric pressure or slightly below. The only way to have positive pressure would be if there was so much blow by that the breathers couldn't vent it, if that was the case, there would be a serious problem with more symptoms.

qwik48r · May 9th, 2008, 09:57 PM

are you sure your motor isnt constipated?

65 B/FX · May 10th, 2008, 11:10 AM

I think I found it. I had my aircleaner off that day and the ram air was going directly into the carb unrestricted. At higher speeds, the airpressure was enough that it stopped or disrupted the flow from the PCV valve and caused that bank valve cover to load up with pressure.
And to the smartass who wants to know if my motor is constipated?....No, but I am. To much whiskey and Fritos

May 8th, 2008, 10:12 PM	#1
65 B/FX Newbie Join Date: Mar 2007 Location: Orange County, CA Posts: 47	Pressure in my valve cover!? Anybody know why Id get a ton of pressure buildup at higher rpms in my Valve cover (PCV side)? Doesnt happen on the other side, and my PCV is new and check out ok. Could this be rings that arent sealing and at high revs the pressure gets too high? It blows out my valve cover gasket and you hear a "whistling sound" until it idles again. Gets some oil on my intake too. The other side has a breather and seams to be ok. Im stumped. __________________ 1964 Falcon Sprint 4 speed 1965 347 Cyclone 4 speed, B/FX clone 1993 Mustang Cobra (red/grey cloth)

May 9th, 2008, 12:08 AM	#2
ryans88gt Hardcore Enthusiast Join Date: May 2007 Location: Bloomington, IL Posts: 2,975	get a new breather __________________ 89 LX 515 hp 497 ftlbs 88 GT 11.4 @ 118

May 9th, 2008, 12:40 AM	#3
65 B/FX Newbie Join Date: Mar 2007 Location: Orange County, CA Posts: 47	breather tests fine. Any other ideas? __________________ 1964 Falcon Sprint 4 speed 1965 347 Cyclone 4 speed, B/FX clone 1993 Mustang Cobra (red/grey cloth)

May 9th, 2008, 02:12 PM	#4
ryans88gt Hardcore Enthusiast Join Date: May 2007 Location: Bloomington, IL Posts: 2,975	If your breather works fine, then you have no pressure under the valve cover. __________________ 89 LX 515 hp 497 ftlbs 88 GT 11.4 @ 118

May 9th, 2008, 04:46 PM	#5
trueblue01 Regular 1989 Mustang LX 10.98@126.7 NA Join Date: Feb 2008 Location: N.E. Ohio Posts: 292	Crankcase and inside of valve covers (both sides) are in common atmosphere. Pressure is the same. Ring blow by comes out the bottom of the cylinder into the crankcase. __________________ Never fast enough.

May 9th, 2008, 04:52 PM	#6
qwik48r Hardcore Enthusiast 08 GT Join Date: Jan 2008 Posts: 1,135	sounds like valve blow by.... take a compression reading of the problem bank. __________________ everyone's a gen-ious around here... 08 Black GT 5sp. Hurst.Pypes.Motive.Nitto(wrong kind, and for sale!!).Mobil1 02 GMC Sierra ECSB. TR.Pacesetter.CompCams.Crane. Richmond.Eaton.K&N.Performabuilt.FlowCrapster. Nelson Tuned!

May 9th, 2008, 05:53 PM	#7
ryans88gt Hardcore Enthusiast Join Date: May 2007 Location: Bloomington, IL Posts: 2,975	IF you had enough blow by, either from rings or valve seals, that a valve cover breather wasn't enough to vent (figure more than 200 cfm), then you would have more serious problems than a leaking valve cover gasket. Like burning 2 quarts of oil a day. __________________ 89 LX 515 hp 497 ftlbs 88 GT 11.4 @ 118

May 9th, 2008, 09:57 PM	#9
qwik48r Hardcore Enthusiast 08 GT Join Date: Jan 2008 Posts: 1,135	are you sure your motor isnt constipated? __________________ everyone's a gen-ious around here... 08 Black GT 5sp. Hurst.Pypes.Motive.Nitto(wrong kind, and for sale!!).Mobil1 02 GMC Sierra ECSB. TR.Pacesetter.CompCams.Crane. Richmond.Eaton.K&N.Performabuilt.FlowCrapster. Nelson Tuned!

May 10th, 2008, 11:10 AM	#10
65 B/FX Newbie Join Date: Mar 2007 Location: Orange County, CA Posts: 47	I think I found it. I had my aircleaner off that day and the ram air was going directly into the carb unrestricted. At higher speeds, the airpressure was enough that it stopped or disrupted the flow from the PCV valve and caused that bank valve cover to load up with pressure. And to the smartass who wants to know if my motor is constipated?....No, but I am. To much whiskey and Fritos __________________ 1964 Falcon Sprint 4 speed 1965 347 Cyclone 4 speed, B/FX clone 1993 Mustang Cobra (red/grey cloth)

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