PVC/Breathers/Oil Fill ?? Confused!! - Page 3 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dakman · 11-24-2009, 07:13 PM

I'd like to see a pic of the T-connection you are talking about for the trany and PCV. My thoughts are... if you are only tapped into one runner on the manifold and supplying both the PCV and trany vaccumme from it then maybe when you get on it and the trany is shifting you may be starving the PCV system badly leaving the crank case pressure no where to go. The PCV should tap in at the base of the carb so it has a continous vaccumme from all runners below the throttle plates. I would seperate the trany and PCV and ensure they are on different sources. Just a guess?

Based on your picture...another way to make the PCV system more efficient would be to move your PCV to the opposite end of the valve cover opposite the breather so it has to cross feed the crankcase. Maybe having the PCV drawing out at the back of the engine where the breather is also located is allowing the front end of the crank case to build higher pressure.... again just a guess.

PowerPro · 11-25-2009, 03:09 PM

One other thing to check - pull out your dipstick and see if you have air coming out or being sucked in. This will tell you if you have a lot of air pressure build-up from blow by in your bottom end easier. If it's sucking in or nothing, you're good. if' it's blowing out, you have some serious blow by and probably need to yank the engine...

hayhauler71 · 11-25-2009, 05:18 PM

I think if it had that much crankcase pressure it would blow the dipstick out and spray oil. By reading all this i would have to say it is a bad gasket job, over torqued fasteners, or a bad chinese timing cover or seal. I have read a lot about aftermarket timing covers having the oil seal off centered in the cover. Does your balancer have a wear grove in it maybe you need a speedy sleeve?

72step · 11-26-2009, 12:15 PM

I just wanted to add a thought to all of this regarding sufficient vacuum: I think it's pretty safe to say you're not leaking oil at idle up to 3k RPMS. Well when you get on it at higher RPM's when you're likely leaking more oil you have to imagine there's much more vacuum than at idle/lower RPMs. In other words when the RPM's are such where you're leaking oil is the point where you're PCV is experiencing more vacuum so I doubt it's your PCV. I currently only have a breather on each valve cover on my high perf. 327 and it has dirtied the valve covers over time but not oil all over the place like you're explaining. Matter of fact the oil doesn't even reach the firewall/inner fenders much. Just enough to pretty much get the valve covers. I'm actually in the process of running a PCV to one valve cover and just leaving a breather on the other to alleviate this so I can clean up my valve covers. Who put together your engine? Perhaps whomever installed the rings just fumbled on one of them? Was the block actually rebuilt that you know of?

11-24-2009, 07:13 PM	#51
dakman Registered User Join Date: Jun 2008 Location: Ontario Canada Posts: 139	Re: PVC/Breathers/Oil Fill ?? Confused!! I'd like to see a pic of the T-connection you are talking about for the trany and PCV. My thoughts are... if you are only tapped into one runner on the manifold and supplying both the PCV and trany vaccumme from it then maybe when you get on it and the trany is shifting you may be starving the PCV system badly leaving the crank case pressure no where to go. The PCV should tap in at the base of the carb so it has a continous vaccumme from all runners below the throttle plates. I would seperate the trany and PCV and ensure they are on different sources. Just a guess? Based on your picture...another way to make the PCV system more efficient would be to move your PCV to the opposite end of the valve cover opposite the breather so it has to cross feed the crankcase. Maybe having the PCV drawing out at the back of the engine where the breather is also located is allowing the front end of the crank case to build higher pressure.... again just a guess. Last edited by dakman; 11-24-2009 at 07:22 PM.

11-25-2009, 03:09 PM	#52
PowerPro Registered User Join Date: Sep 2009 Location: Spokane, WA Posts: 68	Re: PVC/Breathers/Oil Fill ?? Confused!! One other thing to check - pull out your dipstick and see if you have air coming out or being sucked in. This will tell you if you have a lot of air pressure build-up from blow by in your bottom end easier. If it's sucking in or nothing, you're good. if' it's blowing out, you have some serious blow by and probably need to yank the engine... __________________ 1970 C20 LWB Fleetside with a 472 Caddy engine! TH400 Restoration in progress 07 Yamaha 650 V-Star Custom 83 Honda V-45 Magna

11-25-2009, 05:18 PM	#53
hayhauler71 Registered User Join Date: Aug 2009 Location: St. Paul MN. Posts: 1,996	Re: PVC/Breathers/Oil Fill ?? Confused!! I think if it had that much crankcase pressure it would blow the dipstick out and spray oil. By reading all this i would have to say it is a bad gasket job, over torqued fasteners, or a bad chinese timing cover or seal. I have read a lot about aftermarket timing covers having the oil seal off centered in the cover. Does your balancer have a wear grove in it maybe you need a speedy sleeve?

11-26-2009, 12:15 PM	#54
72step Registered User Join Date: Nov 2000 Location: chimayo, nm, usa Posts: 898	Re: PVC/Breathers/Oil Fill ?? Confused!! I just wanted to add a thought to all of this regarding sufficient vacuum: I think it's pretty safe to say you're not leaking oil at idle up to 3k RPMS. Well when you get on it at higher RPM's when you're likely leaking more oil you have to imagine there's much more vacuum than at idle/lower RPMs. In other words when the RPM's are such where you're leaking oil is the point where you're PCV is experiencing more vacuum so I doubt it's your PCV. I currently only have a breather on each valve cover on my high perf. 327 and it has dirtied the valve covers over time but not oil all over the place like you're explaining. Matter of fact the oil doesn't even reach the firewall/inner fenders much. Just enough to pretty much get the valve covers. I'm actually in the process of running a PCV to one valve cover and just leaving a breather on the other to alleviate this so I can clean up my valve covers. Who put together your engine? Perhaps whomever installed the rings just fumbled on one of them? Was the block actually rebuilt that you know of?



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