jpc647

So a 1972 Cutlass from the factory had hoses on each valve cover, one running to the air cleaner, and one running somewhere else(probably to the carb).

I'm chasing down oil leaks, oil leaks only after going WOT a couple of times, or cruising on the highway at 75 mph. The car remains bone dry if I drive normally, never go above half throttle, etc.

If aftermarket covers are put on, say M/T anodized covers, and only one is punched out for a PCV valve and that is running from the PCV valve to the carb, it this going to present a problem with pressure in the motor? Why?

Is one "vent" out of 1 valve cover sufficient, or does the motor actually need both? If both are needed, could I just punch out the second hole and use a breather element? How can I tell if pressure is to high in the motor?

RhinoGTO

I was having a similar issue recently. I put factory valve covers back on and now run 2 pcv valves and T'd them together and run them both to carb. No more leaks. I was running breathers before. And was getting oil spewing out at high rpm.

MDchanic

Well, yeah, because one line goes in and the other goes out.

If you only connect the "out" line, which goes through the PVC valve into the intake manifold, through the port below the carburetor, then there is now way for the PCV to draw air into the engine and clear the crankcase, and the crankcase will be under vacuum, which, under some circumstances, may tend to pull oil into the intake.

- Eric

jpc647

Was oil spewing out of the pcv valve, or from other seals too, like the valve covers, or dist. "o" ring?

I'm having a hard time following what your saying, mostly I think, because my setup is different. The PCV valve line on my valve cover goes into a port on the bottom of the carburetor, not into the intake. But your saying without the air coming in from from the air cleaner, the engine can't clear out the crankcase, so my only or best solution would be to go back to factory setup? Not add a breather element to the other cover, but go back to the OEM steel overs, original carb, and air cleaner?

I'm not getting oil in the intake(that i know of), but it'll leak out of the covers and such at high rpms.

RetroRanger

If its only leaking out the VCs after WOT maybe your oil return holes are partially blocked in the heads. When I changed my VC gaskets I cleaned them out pretty good and then changed the oil.

What eric is saying is the PCV goes to the carb and is under vacuum. The other valve cover should have an air inlet to discourage that vacuum and hopefully create an equilibrium. With just a breather the atmosphere in the engine can sometimes be at a greater pressure than the external atmosphere and as a result spew some oil, with a factory style to the air cleaner breather the spewed oil would just be burnt by the engine.

oldcutlass

I would go with your thought of putting a breather in the opposite valve cover and see if that helps your issue. Another suggestion is to plumb a line from the opposite valve cover from the PCV, to your air cleaner housing, which will give you a bit more vacuum within the engine, I did this on the old 330 that was in my car and it worked great.

One other thing, hopefully your V/C's have baffles or you will have other issues.

RhinoGTO

[QUOTE=jpc647;462909]Was oil spewing out of the pcv valve, or from other seals too, like the valve covers, or dist. "o" ring?


I was only getting oil coming out of the Valve cover breathers. It may be because a lack of proper baffeling as someone mentioned, it may also have been from old dried out pcv grommets. I went ahead and put in 2 grommets on both valve covers and run 2 pvc's and T them into one vacuum line into the front of the carb. It works great for me and its clean and no more leaks.

I was not getting oil from dist or valve cover gaskets. I thoroughly checked, I just rebuilt motor and resealed everything just prior to problem. But i had switched to the factory valve covers from old edelbrocks.

Just giving my two cents on what worked for me, not saying whats right or wrong.

Octania

Read up on the PCV system in the CSM or Chilton's or whatnot.

Normal part throttle operation- air is drawn into intake at carb base thru pcv valve, which is a throttling valve. Air must enter thru a breather/ filter, typically [1969+] located in the other rocker cover.

However, under heavy load, high speed extended driving, WOT or nearly so, with weak rings, the production of blow-by can exceed the ability of the PCV valve [now at little or no vacuum] to draw it in. In this case, the excess fumes are supposed to be allowed to go "backwards" - up thru the "incoming" filter in the RH rocker cover, thence thru that bent steel tube to the rubber grommet in the side of the air cleaner. The gasses then are inducted thru the air filter into the engine and used for combustion.

At no point is the blowby supposed to pressurize the crankcase to the point where it can spew out uncontained. Eliminating the factory engineered parts like the RAC breather to air cleaner housing tube and grommets defeats the proper operation of the system.

jpc647

Thankfully they aren't. I looked at them and posted pictures in another thread and they are very clean. After taking the valve covers off, both heads look very very clean, no gunk or buildup of any kind. I was quite surprised. I would be the heads have been off the car at some point in it's life.


I have an aftermarket edelbrock air cleaner, so I can't plumb anything over to it. But I might try the breather element idea. Not sure if I'll drill out the punch hole in the M/T cover, or just go back to the factory covers at this point, but it might be worth a shot. If they are creating too much pressure at high rpms by not getting the fumes out, could explain some of the leaks.


Thank you very much for this description. It seems as if I'll be changing back to the factory covers and trying this. It certainly seems like Oldsmobile engineered the system in such a way it would work without problems for a long time, even when the engine became "worn". Looks like I'll be playing with valve covers one last time here.

First I just gotta find the new grommets for the stock Valve Covers, hopefully don't have to order them through Fusick or year one.

hookem horns

How about a simple push-in vented cover on one side and PCV connected to cab vac on the other. Works for me.
http://www.summitracing.com/parts/SUM-G3400/

droptopron

Two notes on this
- does you valve cover have a baffle in it? Without it oil will go all over the place
- I have MT valve covers. I have a PCV on the driver's sdie & a push in breather on the other with a hose coming out. I have a chrome air cleaner and the base had a punch out & a fitting to run the hose to on the under side of it.

jpc647

That would work, but the passenger side valve cover doesn't have the perferated "plug" punched out yet. I have to take it off and do that, thats what I was trying to explain. sorry.


The cover does have a baffle. I made a bigger one especially for it when this all first started. I have a chrome edelbrock air cleaner, I never noticed a punch out for a hose on it. I'll look tonight, that would be perfect, and significantly cheaper than having to swap valve covers again. In case it's not there, can you post a picture of the air cleaner you have, a cheap aftermarket one might be cheaper than having to go back to stock OEM stuff.

hookem horns

Maybe as a temporary test put a vented cap on the oil fill tube at the front of the engine (or go redneck with a red shop rag). Pretty sure a PCV system needs that vent somewhere.

jpc647

Thats a fantastic idea! Thanks. I'm going to try that. Looking for one now at local parts stores. Thanks!

jpc647

Well I tried to $5 vented oil fill cap tonight, and the results were sort of shocking.

There is now oil in ethe vent cap, so I'm thinking ither, A) there is still too much crankcase pressure, or b) I have a severe case of blowby. The car runs really, really well. I do have a flat spot on acceleration right from the get Go at WOT, but the car will lay down rubber for 140'+(I only did it one time after testing and tuning the carb).

If the motor was worn out, and suffering from blowby, wouldn't it not have as much power? I checked the drain ports under the valve covers, and they look really really clean. What else could be causing this? Is it time to take advice from the Tuners, and run a catch-can? haha.

Can I see a picture or two of your setup? Wondering if maybe I'm setup wrong, or backwards and that's why I'm having problems.

*edit**
http://shop.advanceautoparts.com/web...earchTerm=2079

I'm thinking this is the part I would need to connect to the air cleaner in order to run a hose from the other valve cover to the air cleaner. I'm guessing I would also need another pcv valve, or the push in breather you mentioned before.

If oil is coming out of the fill tube now, with this breather, It'd imagine if I connect a hose from the other VC to the air cleaner, then the Air Cleaner is going to fill with oil, and I don't really want that. No sense in clogging at $20 filter for no reason.

What could be causing the excess pressure?

jpc647

double post.

droptopron

That is exactly what I have. My car is in the garage & when in there it isn't too easy to get to the hood. My air cleaner base (no name chrome 14" drop base) had a provision in the base to punch out for that.

RetroRanger

here is my set-up CO approved

https://classicoldsmobile.com/forums...ok-w-pics.html

jpc647

So it's worth trying to put the breather element in the air filter and connecting the tube to the port on the air cleaner.

My vented oil cap is really not going to do anything, it's not going to allow fresh air into the motor or anything, just an easier means of escape for the pressurized oil rather than the seals.

Looks like I'm pulling off valve covers again.

oldcutlass

Set it up the way we suggested, the additional vacuum that's created through the air cleaner housing will help with your blowby issue. You already have the valve covers and all you need is the adapter, some hose, a rubber grommet, and a means to connect it to your valve cover.

Might I suggest this:

http://www.summitracing.com/parts/MOR-68781/

jpc647

Thanks for the link. I ordered the grommets, should be here tomorrow or saturday.

One last question, what would the dfference be between the breather you posted and this:

http://shop.advanceautoparts.com/web...earchTerm=4420

The one from the link I posted, this would attach right to the grommet in the cover, allow for air to come in just as if it was coming through the air cleaner, the tube, and both adapters, right? with your setup, what prevents oil from being drawn in through the carb too, the air filter?

The air cleaner I have has a marking for the adapter I need, but it isn't perforated or anything, so I need to drill them out, etc. Just wondering if I could use the edelbrock breather for the same purpose.

If not, what's the difference?(Not sarcastic, serious question).

oldcutlass

You cannot connect that breather to your air cleaner housing. The extra vacuum that you will get will help keep the fumes and oil in check.

jpc647

I suppose I was confusing in my post. I was asking if I could connect the edelbrock breather element in my post to my valve cover grommet, and create the same affect and running all the hardware up to my aircleaner.

oldcutlass

No it will not have the same effect as connecting the one I suggested to the air cleaner.

jpc647

Okay thanks. And your sure that one will fit in the grommets for the valve cover?

oldcutlass

It should give the dimensions on the link, most grommets are standard.