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Oil coming out of Dipstick and breather?PCV valve?

02-24-2004, 09:58 PM
When I first got my 350 on the road, I had the old style valve covers and I just ran 2 breathers and on the one had a hose running to the place on the front of the carb (for vacuum, if that did anything or not) and no problems. Then someone told me I needed a PCV valve. So I put a grommet in one of the valve cover holes and ran the hose to the same place on the carb of course and I noticed my idle RPMs went down a lot. So I adjusted it back up and a few days later I noticed oil coming out of the breather on the other valve cover. So just today I put a regular oil cap on it and not long after that, oil was leaking out of my dipstick. So now I have the breather back on because the oil leaks less out of that.

Does anybody know whats wrong? Do I have a wrong PCV valve or something? Do I even need a PCV valve on my engine. Can anybody explain this? It sounds like I have too much pressure in my crankcase, but I thought thats what the PCV valve is for. I need some help, any would be greatly appreciated, thanks a ton.

Ryan Washington

02-26-2004, 10:54 PM
You are correct in that there is too much pressure in the crank case. Engines need both a PCV valve and a breather.
The PCV valve just allows a small amount of air to be drawn into the engine. This valve helps ensure a flow of fresh air into the crank case. Without it, your engine oil would get contaminated by blow by past the rings and eventually the engine would wear out prematurely.

However, most engines will, at times build more pressure than the PCV valve can handle, so the excess needs to be vented through the breather. Put the breather back on. As for the oil, there should be a baffle in the valve cover to divert most of the oil. If the baffle is missing, (sometimes it is in cheap valve covers) or if you have lots of blow by, oil will come out the breather. Its not a problem unless the amount is excessive. Try reversing the position of the pcv valve and the breather, if you can.

BTW when you just had the hose going to the bottom of the carb, it was like having a massive vaccuum leak in the intake manifold. It would disrupt your carb jetting and performance. You did the right thing by adding the PCV valve.

02-27-2004, 07:25 PM
Yeah but even with the PCV on one valve cover, I still have oil coming out the breather on the other side. So I thought maybe I'm using the wrong PCV valve. I work at advance auto parts and there is a bunch of PCV valves there, I thought they were all the same, are they? I know I could look it up for my 1970 Monte Carlo but I wanted one with a 90 degree end on it. With no PCV valve and just 2 breathers I remember no oil came out. So maybe I do have the wrong PCV. Does anybody have any part numbers to give me? And yes, the valve covers do have baffles in them. And if I don't have the wrong PCV, then how come I could have possible excessive blowby on a fresh engine with new rings and pistons and all? All help appreciated. Thanks

Ryan Washington

04-19-2004, 11:18 PM
well personally ive never heard of ANYTHING like that happening, hehe. but just to help ya, all pcv's are the same, one just looks dif than the other. as long as u have gotten it to fit into the grommet ur good. if u wanna check if its working, run ur engine and pull the pcv while leaving it connected to the hose. plug the end of it with ur thumb and u should hear quite a distinctive click. if it is faint enough that u have to put ur ear next to it then consider buyin a new one. if this is the case check for a vaccuum leak. run a vaccuum gauge to any free vacuum port and if u have anywhere from 20 lbs and up ur good. if it reads 0 snap the throttle and it should go up, this is ur vaccuum advance port for the distributor. if all this comes out good, put the pcv back on and the breather on and empty all the oil. run a hot oil flush or there are even things u can put in ur engine that u run in ur engine as oil for a short while just to eat away all the shit in there and refill it with oil, make sure u dont overfill!!!! if u do the crank will bubble the oil like milk with a beater and u will leak oil everywhere and might even sieze the engine. you see the engine may have not been rebuilt EVER, so theres a lot of old oil and built up grease in there cloggin everything so the oil has no where to go but up and since the oil is pumped up to the heads, when u plug the holes for it to go out of(the pcv and breather) it goes out of the dipstick. so if all this doesnt help u might need a rebuild...sorry togive ya bad news.


06-16-2004, 07:06 PM
Some PCV valves may actually perform differently than others out there... I had a PCV valve dilemma with my El Camino. It wasn't opening at all. Turns out different valves have different "check" valves in them.... i.e. different weights, to compensate with different levels of vacum. I have a mild cam, 224,224 flat hydraulic, .484 lift, and my valve wouldn't freakin open because I wasn't pulliing good enough vac. for the heavy valve I had, I changed it and now it works properly.

Sounds like you may have some blow-by issues man... bad rings or sumthin'

06-21-2004, 03:28 PM
MagicRat was right on the money. There was always a PCV Filter in the Air Cleaner to catch all the extra stuff coming out. Lots of oil means lots of blow-by. I would do a compression check if I were you.

06-27-2004, 09:48 AM
could be your PVC is in backwards too. check to make sure you can blow through it in the right direction.

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