PCV problems

burycm · **PCV problems -** 12-17-03, 02:22 PM

Hey guys, have some questions concerning PCV problems. I seem to be burning oil through the pcv system. I have a 306 pro bullet short block, windsor sr. heads, cobra intake. I am burning oil and I am pretty sure it is through the pcv system. just wondering if anyone else has had similar problems or know hove any suggestions about what to do. I would appreciate any comments. Thanks.

**blown5.0** · 12-18-03, 05:51 PM

thats a common problem, the issue is oil gets up into the pcv valve then in the intake then gets burned. the issue is either a missing baffle under the intake or poor crankcase breathing system trapping pressure inside. the fix is the plug the pcv valve off, then get at least one breather on a valve cover, like the one that replaces the existing oil fill cap and has a breather filter on it.

burycm · 12-19-03, 01:43 PM

I tried that and it did not seem to help. All that that seemed to do was just let it build up enough pressure to actually spit oil out of the breather cap. I did check under the pcv valve and the baffle is still in place. I have 1.6 roller rockers, under stock 302 valve covers, the baffles in the covers were cut to clear the rockers, therefore I plugged to line going out from the oil fill stem travelling to the throttle body. I believe that oil was originally travelling through this hose, so I eliminated it. Without this line and without the pcv valve going anywhere, wouldnt this hurt the system, doesnt it need something other that the breather cap? I guess mabye I do not completely understand the PCV system. I was under the impression though that this system was important and necessary, is that not true?
Anyways, what I tried for the mean time. I cut the line going from the pcv valve and running to the plenum. I inserted a in line fuel filter and continued the normal routing of the line. I have driven the car some with this system in place and some oil is collecting in the fuel filter, so we will see what happens. Thanks for the info though, and mabye you could give some feedback on your opinions of what I have "rigged" now. thanks.

**blown5.0** · 12-19-03, 02:00 PM

well the only requirement is the engine have at least one vent to atmosphere to relief internal engine pressure.

the pcv system is only there for emmisions and enviornmental reasons.

the oil coming out of you valve cover breather is directly related to the fact that you cut out the baffle. since you did that the rockers sling oil up the vent tube onto the inside of the breather and it leaks out from there. so you need the baffle, if you have to get taller valve covers with a baffle to clear the roller rockers then thats what you got to do. once you get that straight, plug the pcv valve off completely. this will solve your problem. and yes the small line on the valve cover tube should be plug as it is not needed. a better option would be to have baffle/breather on both valve covers, but one is enough. but as long as that pcv is connected it will suck oil up thru it so plug it.

burycm · 12-22-03, 07:50 AM

I do appreciate your comments, but from what everyone else has told me, you are wrong. I believe that the PCV system has two functions, one being the emisssions and enviromental issues, and the other as a positive crankcase ventilation to draw out the air, and bring fresh air into the system thus releiving the moisture and stopping rust from occuring inside the valve covers. I think I am going to leave it the way it is for know, but I may change it again if it does not seem to work. thanks anyway.

**blown5.0** · 12-22-03, 09:16 AM

we are both right. yes the pcv systems intent is to use engine intake vacuum to pull air/pressure from in the crankcase into the intake to reburn it, for emmisions purposes. but your problem and half the mustang community's problem is the pcv systems that is suppose to pull a crankcase vacuum also pulls up some oil with it. but the factory system is closed so it does not pull in fresh outside air. basically any ring blowby is drawn up thru the pcv system.
so the fix is to plug the pcv valve off. this gets rid of the oil in the intake but now the motor has no way to vent any internal pressure, thats why there should be at least one breather filter on a valve cover to vent the motor. just look at any serious motor, they either run the high $$ belt driven vacuum pumps, or valve covers with breathers, and none of them have pcv systems.

good luck, but thats the way to do it.

burycm · 12-22-03, 10:41 AM

I do see your argument, and agree. I was hoping to fix the problem without doing valve covers, because of my larger rockers the stock ones with baffles will not fit. I would do taller ones with baffled valve covers, but could not find them, and that would also mean an intake plenum spacer, and that would mean a cowl hood. Just like everything else, never as simple as it appears! thanks for the suggestions. sorry if i came across like a dick, that was not my intent. always open to suggestion.

**blown5.0** · 12-22-03, 11:49 AM

you didnt come across bad at all so dont sweat it. I here you about tall covers, then spacer then cowl hood.

I have those compcams composite valve covers which are std height and could not fit baffles either, and I have no pcv system with my edlebrock performer rpm air gap and 650 race demon, so what I did was drill a hole in each valve cover for a rubber pcv type grommet both in the front of the motor and got two 90deg plastic elbos plugged them and connect the from one cover to the other with some heater hose and in the center I have a T with a small breather facing up and that works great, any splashed up oil just lays in the bottom of the hose a drains back in the valve cover while any air is vented out. had this with efi too and I just took an old pcv valve and capped it off. so you might do the same but on the pass side cover use the exist side hole and stock oil cap. you may even get away with the stock oil cap and a breather right on the stock hose nipple on the pass cover and leave the drivers side stock.

I am getting rid of my valve covers and breather setup because that type of breather system is not legal for SCCA racing, needs and overflow tank, will be getting the tall motorsport covers with 90 deg #12an braided hoses from each cover feeding a 1 quart breather/overflow tank.