Oil in PCV system?

[Bob Gervais]

87 Sub, 350 TBI, bone stock.

This truck has always puffed a little at startup, so I knew the day would come when I'd have to do the valve seals. I've been putting it off as long as possible though, tending to other problems with the truck instead.

Recently, it started smoking while running, intermittently. Weird, I thought, if it were the rings it should smoke pretty steadily.

By chance, I checked the PCV. It was loaded with oil, so I installed a new one. Still smoked occasionally. As an interim fix, I teed in an old air compressor separator/filter I had kicking around the shop, so that the oil would deposit there instead of getting sucked all the way into the TBI and smoking. In my 70 mile round trip commute to work, I've been dumping out about three to four ounces of oil from the separator. The tube that goes from the driver's valve cover to the TBI air filter spacer is pretty soaked with oil as well.

This seems to have come on all of a sudden, I never had this issue before. I don't know the previous history on this truck, but I know since I've had it the oil gets changed, at a maximum, every 5000 miles.

Is it possible the oil return passages are partially blocked, and more oil than normal is sitting in the head? If so, has anyone had this problem and solved it any other way than pulling the valve covers and oil pan and running some engine cleaning brushes through the passages?

Thanks in advance for any help.

[edman87]

sounds like your motor is just worn, too much blowby. time for a rebuild

[Bob Gervais]

I was thinking the same thing, but this just happened too quickly. One day it was fine, the next it was doing this. This weekend I'm going to do a compression check on it, and see what I find.

Maybe the stroker motor is closer than I thought.

[edman87]

do a leakdown test on the clys, that should decide it.

[edman87]

that was cyls, my bad

[Bob Gervais]

It's OK, I knew what you meant.

[bisquik65]

Take your tbi off,and check the passages under it,make sure the pcv is not plugged up with carbon,this will cause the oil to bo forced out somewhere...EZ to do...And valve seals will smoke while running if they are really bad..You may want to do that soon too..Hope this helps,Erick

[Bob Gervais]

Well, compression checks out OK. All cylinders within 10%. I'm in the process of making a leakdown tester from some instructions I got online, and will use that to check as well.

It also seems that some oil is making its way into the vent tube that runs from the TBI spacer to the driver's valve cover. My oil pressure gauge is very erratic as well, which is making me think even more that something's clogged somewhere. Either the TBI passage as you mentioned Erick, or the oil return holes.

Either way, I need to make a trip to MD toward the end of summer, so I'll need to get this resolved. In a couple weekends from now, I'll be pulling the valve covers, installing new seals, and cleaning out the oil return passages. I'll take off the oil pan and clean off the pickup screen too, and hope for the best.

From reading another post regarding stalling, I should probably throw in a new distributor as well.

I actually drove an 86 3/4 ton diesel the other day, that's for sale locally. Thinking that mine is not worth throwing any more money at, I thought it might be a good idea to get the diesel. It seemed a little too sluggish though. Maybe a trait of the diesel, but it didn't feel as strong as my gasser. Came to my senses and decided to fix mine.

[edman87]

I actually had the throttle body plug up in my old 91 4.3, it blew the valve cover gaskets(neoprene) out, twice, before i figured out what was wrong. If you want to check this, just pull the 3 bolts on the trottle body, and check the ports under the bottom. Very simple and the gasket is almost always reusuable. If it is plugged up, use a small screwdriver and some carb cleaner and go to work on it. The throttle body assy. is very very simple.

[Bob Gervais]

Maybe it's too early, or I'm just plain ol' dumb. I'm not understanding how the plugged up throttle body could make it pull oil through the PCV valve. There's vacuum at the PCV.

Again, my apologies for not understanding.

[edman87]

If the ports on bottom of the throttle body is plugged, the pressure inside the crankcase has no where to go, so it creates a way out and takes engine vapor and oil with it. I would say the pvc system is not your problem, but it never hurts to check.

[Bob Gervais]

Makes sense now, thanks very much.

I've installed an inline oil separator, which is usually used on an air compressor, in the PCV line. I empty it every day, and there's about 3-4 ounces of oil in it. Since there's oil getting sucked through the PCV vacuum hose and valve, I assumed that it was because there's excessive oil under the valve cover, sitting on top of the head. I then assumed that the only way this would be possible is if the oil return holes are partially plugged up, and not letting the oil drain back into the pan.

Does that make any sense, or am I making the wrong assumptions?

Thanks again for all the help!

[edman87]

Most engines have some amount of blowby, very little is good. some amount of air and vapor circulates through the crankcase( bottom end) and lifter valley and valve covers. If the pvc is plugged the air and oil vapors will take the easiest path out of the engine- like with my 91. With a "good" engine, there is very little blowby and the oil rings keep the oil from getting into combustion chamber, so...no smoke. When ring/ pistons/cyl walls are worn or damaged, you get more blowby/more oil in combustion chamber--more smoke, and more oil in the pvc system to go back to the intake, like in your situation.
I know this sound like a book, but I think it explains you dilema. The leakdown test is a pretty good indicator. I had a 305 carbed that started to smoke and got worse fairly quick. I did a "re-ring" job on it- honed cyls, hand seated valves,new rings and gaskets- and it was like new. Couple days work and 100 bucks. Yuors will be a little more because of the gasket design, but still less than 200$ if that is all you do. I would say go more in depth with it if you want to keep it for a while. If no machine work is done, the new rings wont last as long as original. Keep us posted on your plans and good luck.

[Bob Gervais]

re-ringing sounds like a good option to hold me over for a while. I'm used to front-drive V6 engine removal, and working on pain in the neck cars. The Burb engine looks fairly easy to pull in comparison.

I was already going to do valve seals, and since we're only looking at a couple days of work, I think I'll just go ahead and do what you suggested.

The truck is rusty, but it's all easily replaceable stuff: doors, tailgate, rockers are just starting, and rear quarters.

We've put over 6000 miles on her this summer, just doing road trips to FL and MI. Plus, it's been my DD for a month now, due to brake problems with my other car. I drive 70+ miles a day for work, and she's given me no other issues. To me, it's worth repairing because I know the history of the truck. My only other option is to throw $2500 at something that I don't know the history of, and could possibly end up in worse shape financially.

Thanks for all your advice guys, I'll let everyone know how I make out with it. Possibly some pics too.

[edman87]

I know the feeling, you should be able to do a re-ring in a little spare time for low$$, and if engine has no other issues(knocking, grinding etc)
i would say a set of rings, rod and main bearings, new gaskets and lapping in the valves should make you very happy. Changing the oil pump is your choice, but recommended and keep a eye on the oil pressure when you put her back on the road, if you have only a light, install a guage

[Bob Gervais]

You've convinced me. I'm in the process of putting together the parts I want to order, bearings and an oil pump are on the list, too. May as well, since I'll have the engine out. I'm also thinking about installing a different cam, just need to find an emissions legal cam that will work with the TBI. I'm sure that won't be hard to do. Speaking of TBI's, I may end up modifying that too while I'm at it. I had found a company that does high-flow TBI's similar to the Holley setup, but at a lower cost. I need to find them again, and send off my TBI while I'm doing this other stuff.

Thanks very much for the help!

[edman87]

I know there is an edelbrock cam package for the tbi, that will not require computer mods. I have heard that computer mods are not that complex or expensive if the person doing it has the correct knowledge, but don't know anyomne that has had it done. Check coloradok5, alot of guys on there seem to do stroker conversions and have computer mods to support the engine. Good luck with it all.