The Stovebolt Site Forums The Shop Area Engine Shop Oil Blowback On 261

I am getting some oil vapor and oil blowback from the filler cap on the valve cover of my 62 261. I think I have a problem with crankcase ventilation? It almost stops at idle add rpm and it gets worse.

What should I check and how should I fix it? The engine is not burning blue out the exhaust or anything like that.

Thanks!

Your piston rings are shot. Check the road draft tube. Make shure it isn,t stopped up.

Thanks, I pulled the road draft tube and cleaned it with gas and checked all the tubing over to the manifold. Changed the oil...dirty to say the least. Warmed the engine back up...same problem. Checked the vacuum...very stong, the engine would die when I disconnected the hose.

So.........looks like I have a nice suprise with my new purchase. Could you recommend a good thread or source for installing new rings with the engine in the truck? I don't have a cherry picker. It will have to wait until spring. I don't have a heated shop.

Spuds,

Would it be wise to take a compression check before you did anything else. There was a post on this procedure several days ago.

If you aren't burning oil and smoking the neighbors out, there might be another explanation for your problem.


Stuart

I had that happen once on an old Volvo engine in my 1968 wagon. It turned out to be a clogged pcv valve. If the crankcase can't vent it will find the next available opening; it has to vent somewhere eventually. If crankcase ventilation is working then my guess would be ring blow-by. A compression tester could read low for more than one reason. A leak-down tester is made to pinpoint the problem more precisely.

Okay, I will keep looking. If my road draft tube and tubing is clear, what else should I check? I get no smoke at all out the exhaust when the engine is cold or hot. Thats what kind of fooled me. I don't see a pcv valve. The PO said the truck was an original 76,000 mile engine. I don't know for sure though. It has been some kind of service truck might have spent hours running parked or who knows.

I have been around farm trucks enough to know its not the miles but the hours, too bad most old trucks did not have hour meters.

Found a sticker that says it had a valve job at 68,000 mi. Of course that was in 94. The sticker also says to send the S-0-S sample in promptly. I know that is oil monitoring for a large fleet operation. As far as other history I don't know when it left the fleet and what happened to it after that. Thanks for the replies and help.

Just thought of something else. At the top of the road draft tube it gets larger than the rest of the tube. I could pour gas through the tube when cleaning it, but does this larger section contain a valve or something? If so could the valve be sticking with vacuum applied?

Spuds,

No valve in the tube. When you get a chance, do the compression test. I would pull the valve cover and make sure you are getting top end oil (not too much though), and adjust, or at least check valve clearance. After the 68k valve job, the valves might have settled in their seats and your lash could be too tight.

Some folks will say a head rebuild on a high mileage bottom end will spell disaster in a short time. I have no strong opinion on this, but it could explain your problem.

I have always felt that if there was a ring wear issue, you would be using oil, and showing smoke...maybe this isn't the case.

I guess the '62 engine was too early for a PCV valve huh! Keep us posted.

P.S. Love your handle.

Stuart

Okay I will check those items out. I have also heard that for years if you rebuild the head you will blow the bottom end.

I have been cleaning the cab and have found several empty oil bottles............so not sure if it's the blowback or what, but I get no smoke at all. Would you happen to know what the valve lash should be on that engine?

Thanks on the handle... I live in the potato capital of the state. My dad raised spuds on his farm. I work at a plant the processes spuds and we have potato fields on both sides of our house...and I like it.

Harvest is just winding down, it's getting safer to be on the roads again. You know, lots of old trucks with bad brakes and too big of loads headed for the cellars! I know I used to drive one growing up. I enjoy the harvest time though equiment is lot's larger and nicer than we had.

Talk to you later.

Spuds,

I found this doing a search.

"261 cubic inch

Intake: .006

Exhaust: .018 (up to 1 ton trucks); 020 (over 1 ton trucks)"

This is of course for a solid lifter engine.

Stuart

Does it have a vented oil cap? Some of the heavy duty engines of that era had PCV valves. Why not try a can of Piston Seal or something similar. It worked for me on a Y-block Ford a couple years ago.If you won,t be starting it in cold weather you could use a heavy oil like 15/40 or 20/50.

Yes, it does have a vented oil cap with what looks like steel wool in it. Where should I check for that PCV valve? Have not seen one in the hoses.

Another thing I found... the rubber line coming from the road draft tube goes over to the intake manifold a usual. Then the lines go into a junction, one line goes to I think the hydrovac brake unit under the driver running board. Under the passenger side there is a large tank which may be for vacuum also, I have not traced the lines out yet.

They have also added a vacuum gauge under the dash, it works and reads about 15 in of vacuum at idle. For some reason they wanted to track the vacuum pressure on this truck.

What's the temperature like out there where you live? Could it just be steam (water vapor) that you're seeing? Just a thought,
Scott

Spuds,

Does the line run from the draft tube to the intake manifold without some type of valve. How would that work? I could see that line going into the air cleaner, but how would it work going into the manifold...how could the engine run with a "hole" open to the atmosphere?

Stuart

It has been running about mid 50's at the max in daytime and low 30's to low 20's overnight. The valve cover has alot of oil build up on it and it is crusty with a wet coat on top.

It saw that when I bought it and I thought maybe they were just sloppy when adding oil or plugged/faulty PCV as I saw no exhaust smoke. Could be steam, either way I am going to run it awhile before I tear into it. I think I will try some of that Piston Seal that Wrenchbender Ret mentioned with the fresh oil and filter change.

Norm

Would it help if I linked up some pictures? Anyone have an interest in that. Me, I like pictures.

Pictures are great. They help educate all of us who can't understand the spoken word!


Stuart

If you have a road vent tube, I don't think that you will have a PCV valve. The blow-by on a well used six is quite normal. If it doesn't smoke and it doesn't fill the cab with fumes, is it really a big problem? A set of rings would probably be of help.

It sounds like you have an actual PCV system on this 261, not a road draft tube. There is a valve.

The road draft tube system doesn't have any hoses at all, just a vented cap and a tube going from the block in front of the distributor down to below the oil pan. Road draft tubes let out quite a bit of funky vapor unless you are moving.

Okay, here are some links to pics. I think you are right I don't have a road draft tube. I did not know what to call it so I just followed along with the name I got after my first post! After I saw the photo of truckernix 51 I knew I did not have a draft tube. Pefect shot of that fresh painted engine with the tube in black in front of blue.

Anyway between all your replies I am getting closer. Question, where is that little beast of a PCV? Thanks, here they are.

http://i115.photobucket.com/albums/n282/spdzrus/connecttomanifold.jpg

http://i115.photobucket.com/albums/n282/spdzrus/connecttomanifoldclose.jpg

http://i115.photobucket.com/albums/n282/spdzrus/connecttometaltube.jpg

http://i115.photobucket.com/albums/n282/spdzrus/connecttometaltubeclose.jpg

http://i115.photobucket.com/albums/n282/spdzrus/connecttometaltube-far.jpg

http://i115.photobucket.com/albums/n282/spdzrus/Tubefromtoptomanifold.jpg

Sorry about that dirty engine, I have not had a chance to degrease it yet.

Spudz,

Cool pictures...definitely worth a bunch of words! At first I thought the crankcase ventilation system was home made, but maybe not.

In my humble opinion, there has to be some valve or something in that line from crankcase to manifold. I don't think the engine would run with a open tube to the crankcase.

More detective work is required to figure this out. Maybe a big bolt '60's mechanic will appear from nowhere and give us the lowdown.

I wonder if this truck was working in some environment where 'emissions' couldn't be tolerated. In all honesty, the engine does appear to have been rode hard and put away wet.

Stuart

I feel the same way, if I unhook that rubber tube from the top of the large metal one the engine will quit right away. The truck had a lot of equipment welded to the bed at sometime in it's life. Superior Aluminum Body out of San Francisco did the work in '88. It has the stickers on the doors. The whole truck was painted bright orange at one time, I mean the whole truck inside cab, bed, under frame (not overspray but a shiny coat). Could be from a mine or ???? To me that metal tube to the crankcase has got to be restricted in some manner, like you say if wide open the truck should stall.

spudz,

The tube running to the junction block on the firewall is a straightforward vacuum line to the hdydrovac and evidently, a auxiliary storage tank. It should have a check valve in it somewhere that won't allow vacuum to bleed off.

The other line I don't understand. It would appear that the oil fill cap on the valve cover is the ONLY means the engine has to breath, and it is doing it with vigor...all over the valve cover.

I wonder if your rig was a old Southern Pacific service truck. There would probably be SP tags on it somewhere.

Keep us posted.

Stuart

Maybe someone can tell me, that rubber tube hooks onto that elbow with a clamp, then the elbow screws into the metal pipe.

Is the PCV comtained in that elbow? It does have a large space before the hose hooks on. I did not clean that part. Just the tube then put things back together. The hose goes straight over to the mainifold. Nothing is in line.

The PCV valve on a 261 engine was screwed into the fitting that comes off the oil separator tube (the tube that replaced the road draft tube in PCV-equipped trucks).

You can see the PCV valve in this photo - it has the hose clamped to the top and it and it is threaded in the bottom. The PCV valve can be removed, taken apart, and cleaned. There is a photo of the expanded PCV valve-parts in the Shop Manual.

http://i115.photobucket.com/albums/n282/spdzrus/connecttometaltube.jpg

Do you have a tube going from the air cleaner into the valve cover (allows filtered air to be drawn into the valve cover)?

Wow...Thank You.... No, there is no line going from the air cleaner to the valve cover. No hole for a line on the valve cover either.

Spudz,

See, I told you a big rig mechanic would be along to save the day...Sir Tim, from Castle-town.

If you can clean or replace that PCV valve, your top end breather might stop spewing!

Stuart

I'll be glad to trade you a traditional road draft tube for your factory PCV if you want to remove it, but atomarc is on teh right track. Your check valve is probably sludged up and not passing any vapors through it.

Well, went out last night and pulled that PCV valve out. Did the shake test, it rattled. Cleaned it up anyway and put it back. Started up the truck and ran it awhile. Same problem so.....looks like I have a long road ahead.

You may be getting oil splash out the cap if the "wool" in the oil cap is rusted out or saturated. The valve rocker arms can splash oil up and out. I would try replacing the cap before you worry too much about blowby if it isn't smoking much out the tail pipe.

Did you install a hose from your air cleaner to the valve covers? Do you have fittings for a hose on your air cleaner and valve cover?

It looks like you have a breather-style oil filler cap. I could well be wrong, but I think that a PCV system is a sealed system and it does not have a breather-style cap.

Man, this is great...okay I will try that. Where would be the best place to get one?

tclederman, yes it is a breather style cap. No outlet on the air cleaner, in fact I am not sure it is the right air cleaner. Most trucks I saw in my younger days had the oil bath type when they were this age. This has a paper element type. No inlet on the valve cover either. Who knows what they have changed.

Have u pulled the valve cover off to see if there isnt a cracked rod or lifter? Is there oil comin out of the exhaust pipe or manifold? if so they ur rings are fried. same thing happened to my 327 it sat for a year in some old 1 ton out in the trees. ran good until i put new gaskets and a few miles on it.

This option was put on those engins at that time,how ever there should be a valve cover tube to the top of the air cleaner see sect.6 sheet 13.00,sect.0 sheet 4.00. I installed this option on my restored 53 3100,had to make my own parts but love the operation, no fumes while ideling and a great item for discussion at the shows. I think my engine is breathing better now.

Beaver53,

I would be very interested in how you did that. Have any pics? Right now I am considering going to the salvage yard and finding the correct valve cover, oil fill cap and air cleaner. I have no fitting on my air cleaner or valve cover. I wanted the install to "look right".

Maybe I should move over to the swap meet and look for a trade? Shipping may not make it worth it. I have to be a little careful. My wife thinks it's a waste of money and does not like the sight of it in our yard. Don't get me wrong she is great about other things, but not this. Of course I have an old tractor and plow too!

I don't understand how the P.O.'s could drive it like this. That motor is an oily mess and it would drive me nuts. Looks like it has been that way a LONG time.

spdzrus,

You have at least three options:

1. Preferred option: find an air cleaner and valve cover from any original 261 engine (1954-1962). All were supposely fitted with the PCV system. (although, my 261 came off a 1960 large school bus that was not fitted with the PCV system - it was most likely a custom, commercial, order)

2. Next best option: find any air cleaner that fits your carb and also has a tube-fitting for a PCV system; and, either adapt a (your) 55 to 62 valve cover for an air tube, or find a 54-62 261 valve cover with the tube fitting.

3. Lowest preference option: run without a PCV system - get a 54-62 road draft tube and get rid of the PCV hose (and plug-or-change the hose fitting at the manifold).

On any PCV option, use a non-venting oil filler cap. On the no-PCV option, use a vented filler cap (your present valve cover does not have vent "slits").

Tim