I’m trying to troubleshoot an issue with oil consumption on my 302 4V J-Code 68, Auto. The car is using oil. About a quart a tank full. There are no leaks. And, it doesn’t smoke noticeable. The carb is the Autolite 4300.
Compressions are good. It does idle a bit rough, but starts and runs fine. It needs some carburetor tweaks, but that’s not what this is about.
In my messing with the carburetor, taking it on and off, I’ve noticed the cavities on the intake manifold, under the carburetor spacer are full of oil. The only way I can figure out how oil is getting there is from the PVC hose. I have the Scott Drake Cougar valve covers and breather on the car. They don’t use the same oil filler cap and the breather hose running from the breather to the filler cap as stock. The filler cap is vented (it wasn’t when I first put the valve covers on).
The PVC valve seems ok. It seals when it’s blown into and air flows when it sucked on. That means it’s good, right?
So, I’m wondering if there’s too much air flow through the PVC tube going into the carburetor and it’s vacuuming the oil right out of the head. There’s a pretty restrictive cover/splash guard on the inside of the valve cover under the PVC valve hole.
I’m just really confused about this. I suppose I could put a small catch can inline with the PVC hose to trap the oil, but I’d like to keep the engine bay stock looking.
I’m not ruling out leaks in manifold gaskets and such, but with all oil in those cavities under the carburetor spacer, I thought that was the place to start. Like the oil was getting sucked into the cylinders and getting burned. But, it doesn’t smoke in a way that noticeable.
I had that problem with a J code 302 once. It had bad valve guides. Nothing fixed it until I had the heads reworked with new bronze guides. It didn’t smoke at all. But the back bumper and rear valance would always get greasy after a long highway trip.
Funny you should mention oil coming out of the pcv valve. I have the same valve covers and have excessive oil coming from the grommet around the pcv valve continually. It is almost like there is too much pressure forcing oil out in that area. What gives?
Is there a baffle under the pcv valve? I would think there should be something there to keep oil from getting to the valve. If there is one it may be to open so oil is getting sucked in to the valve. You can put your old valve cover on or a stock one to see if this is your problem. And it could be bad valve guides letting oil suck thru them.
Amen. Back in high school, I thought I would take the baffles out of a set of Moroso vcs so it would be faster to fill the car with oil, and voila!, oil consumption. A lot of things can contribute to oil consumption such as excessively rich mixture, vacuum advance not hooked up and/or working properly, and the list goes on.
I have to ask what you mean by baffles? The is a deflector that looks like it would keep oil from splashing directly onto the PCV valve. If you mean something similar to a porous filter that might restrict airflow (there was one of those in the breather where the filler cap tube connected, I don’t have anything like that. The only place I could restrict the air flow would be in the filler cap, or if I jammed some like a scouring pad in the splash shield under the PCV valve. Hmm… Thinking.
The deflector you are referring to is the baffle. Don’t stuff a scouring pad in the splash shield under the PCV unless you want it coming apart and infiltrating your oil. Have you done a leakdown test on the engine? This will tell more about ring seal, leaking valve seals, etc., than a simple compression test. Before I went straight to pulling cylinder heads I would do a leakdown test and at least see what percentage you are losing as far as cylinder pressure.