I just got back from a trip across Chinook Pass(elevation 5000 feet). My old Chev 350 really laid down a smoke screen going down the back side of the pass. It has never done this before. The only thing different than the other trips was I just replaced the oil pump and the oil pressure is higher than before. I think that the rings are bad or the valve stem seals are bad. I can't imagine the higher oil pressure causing the smoking problem. My dad use to have an old Ford that did the same thing and when my friends and I were at the top of a hill we would wait for a motorcycle and get in front of it. At the bottom of the hill I would give it the gas and you couldn't see the rider. One of them got off and stood along the road. Darn kids. I really hope that one of you gear heads can help come up with an answer to the smoking problem. I suppose I can live with it and do nothing. Dennis

Could be either, could be both. If 'twere me, I'd do the valve seals first. Cheap and relatively easy if you DIY. Not terriblly expensive if you have to hire it done. Give it a tryout, and I'll bet you cut your problem at least in half.

If John Law doesn't get you for polluting the air, oil's lots cheaper than ring and valve jobs, though either/both of those are cheaper than buying a new rig.

Thanks for the post. I see that you are in Sequim. I'm in Port Townsend. What kind of a Barth do you have? It would be fun to get together sometime. I'll pull the heads and take them to the machine shop and do a valve job and have the seals replaced at that time. Since I'll have the heads off it would be the time to do the rings. It is a pain to pull the pan. I just did that when I replaced the pan gasket. I do all my own work. Thanks Dennis

There is an old school of thought that says, replace rod bearings when doing a valve job. I know I am old and that school may have changed, but it makes sense to be conserned of the added compression and what it will do to old bearings. Valve seals won't dump added compression to the bearings. Just a thought.

As Roy said, valve guides are a likely area for oil to get in the combustion chamber. Usually intake. This is not as likely, but if you have more oil delivery, it is possible that oil is pooling in the rocker boxes. That can be seen visually as the engine runs, and is usually just a clogged drain passage.

Another likely suspect is the oil control rings being gummed or carboned up. A good motor cleaner in the oil could help. Sometimes squirting carburetor cleaner in each plug hole and letting it sit overnight can loosen them up, too.

Is the PCV valve clear and free?

Is there much blow-by?

What weight oil are you using?

Hi Dennis, Yup, I'm in Sequim. I have a rig, but no Barth, I'm still a Barth wannabe. Have been for years. A little long-in-the-tooth at age 75 to be thinking of new RV adventures, but if the right rig should come along? Who knows?

Been doing all my own work for most of 60 years, but it don't get any easier when the joints get creaky.

I'd like to see your rig. E-mail me at olroy@olypen.com. Maybe we can get together some time.

Hey Dennis, do a compression check before yanking the heads.

How many miles on the engine?

If you were going down the pass, foot off the throttle, and smoking, this points to valve guides and valve stem seals. Pulling the heads and doing a valve job, including guides and seals, should help.

Does it smoke under load, like climbing up the pass??

[This message has been edited by John Ricks (edited October 10, 2003).]

A compression test will tell a lot about cylinder wall, compression ring wear, and valve/seat wear, but not too much about oil control ring problems.

I have pulled down engines with the oil control rings completely clogged solid with carbon. They need to be fairly clean in order to flex and do their job. The problems are related, however, as worn rings/cylinder walls will cause blowby, which contributes to sludge and carbon impeding the function of the oil control rings.

Sounds like all of the posts here are on the right track, though, as the engine parts wear out together.

Consider rings, bearings and a valve job with seals.

Thanks for all the help! I'll do a compression test just to see what pressures are shown. The engine doestn't smoke under a load, at least from what I see coming from the exhaust pipes. I was thinking about the excess oil in the heads. The problem only started after I replaced the oil pump and the oil pressure jumped up. It runs at 60 PSI with the engine warm and 30 at idle. Dennis

Dennis - olroy again. I'll defer to Bill H and John Ricks any time, they're pros, I barked my knuckles as a shadetree mechanic.

If I were in your shoes though, with the history you gave, and in light of all the advice, I'd make step one the compression check. If it passes, I'd pull the valve covers per Bill H, check the oil drains, and with the covers off, replace the seals. Takes a valve spring compressor, and an air compressor to pressurize the cylinder, and keep the valve closed while you mess with it. Lots easier than pulling the heads, the pan, and doing a ring and valve job.

Adjust the valves - The book says tighten one full turn after they're snug. I've been burned worse than my valves by going too tight. I'd go no more than 1/2 turn.

Button her up, drive a few miles, find a long hill to go down, and see how she smokes.

Bill H's ideas about mouse milk in the crankcase and cylinders is worth a try, too, though I'd see what the valve seals accomplish first. Sometimes, if you use cleaner in the crankcase of an old engine, you wash out whatever was keeping the front and rear mains, and the timing chain cover from leaking.

Considering you were satisfied with performance before the new oil pump and the onset of the smoking, if this works, you'll be back to where you were. If it doesn't, keep repeating through clenched teeth, "RVs are fun."

In any event, you'll only have wasted a litte time and effort before tackling the big job. Unless, of course, you're really itching to get down and dirty with the old beast. In that case, skip this post.

I am with Bill H, everything is related.

In my experience, if valve guides are worn, or oil rings are clogged/stuck, then it is time for a full engine teardown. New rod and crank bearings, turn crank, bore block, new pistons, rings, grind valves, guides, seals, etc, cam, cam bearings, timing chain and gears, lifters, the whole shooting match. Don't forget the valve springs, they wear out also. And don't omit the hot tank dip.

Then you have 100,000 miles ahead of you, provided you maintain properly, change oil at 3000, etc.

Throw in a RV performance cam, hedders, big exhaust, mid range torque intake manifold, new carb, some MSD trinkets, extra cooling and you will have 100 extra hp for those long hills.

Then it will be time to trick up the trans.

John is right about the package deal. I guess it depends on how long you plan to have it. (I am going to have a Viking funeral in mine.) I went one step farther and put in a crate motor.

One other thing------if you don't have an air compressor to blow in to the spark plug hole to hold the valves in their seats while you are removing the springs, position the piston at bottom dead center coming up on compression stroke. Stuff as much rope as you can in to the spark plug hole, leaving a "tail". Bring the piston up by hand and the compressed rope will hold the valves to their seats.

The Chevy rocker arms on their ball socket pivots impart a lot of side thrust on the valve stems. This can cause premature wear on the valves stems and their guides. If you pull the heads, consider bronze valve guide liners. They are pretty reasonable.

Consider a Performer manifold and Thorleys if you pull the heads.

A little update on my 350 smoke screen machine. I just did a compression test and all the cyclinders were within 5 pounds of each other. The pressure was 160 pounds in almost every cyclinder. I got to thinking,I know that can be dangerous, about the weight of the oil I used. It was 10-50. Maybe the 50 part was too heavy and that caused the higher oil pressure and the cyclinder walls were not being cleaned by the scraper rings. I'm going to change the oil back to 10-40 before I do anything else. I might change the valve stem seals also. Thanks for all the help. When I see one of those great looking newer rigs for sale, I get motor home envy. Dennis

My guess, the compression is low in all cylinders and since you seem to be using the rig with some regularity I doubt the rings are carboned in position so you probably have a fair amout of wear on both the cylinders and rings.The valve guide seals are probably leaking but that is smoke on starting not running.
My advice is to carry extra oil and plan on buying a reman engine when you decide you are going to have the rig down for an extended time. If you want, I have a bunch of links for reman engines, just let me know.
If you are not traveling a long way from home or into the outback so long as the rig starts and runs and you keep the oil level checked run it. I had a Ford 460 that had a bad oil pressure relief valve. Thinking that with the pan off I might as well replace the rod bearings I opened the pan and found the end play could be measured with a yardstick, the crank could be up and down as well as front to back so I buttoned it up with a new oil pump and ran it for another 10K before selling it and it continued to run for the new owner for at least a year before I lost interest in the story.
Run it til it dies or if you are going to own it for another indefinite period decide you will need a new engine sometime and bite the bullet.


or flip a coin,

Tim

160 lbs. ain't bad, & if they're all within 5lbs. of that, they're very close, indeed.

Was your compression check wet, or dry?
If you did it dry, try pumping a few squirts of oil in each cylinder before you check, and try again. The amount of increase will give you a rough indication of cylinder or ring wear.

Smokin' downhill on a trailing throttle, as
you first reported, means you're drawing oil into the cylinders, either past the rings, or through the valve guides.

As Bill says, the intakes are the likeliest culprits, but once you've got the valve covers off, and start removing the springs, you might as well do 'em all. (one cylinder at a time, of course)

I still say, if it were me, I'd pull the valve covers and check for plugged oil returns, as Bill advised. Then, lacking an air compressor, I'd use his rope trick to hold the valves up, as I replaced the seals.

Relatively cheap, relatively easy, and possibly a good investment in time and money . If it doesn't help, you're no worse off than before. If it does, you're ahead of the game. Just be sure you use name brand seals.

The natural mind-set of the pros is to do it all, and do it right. My mind-set is keep it running as long as possible, before you tackle the major stuff. Once you pull the heads on a high-mile engine, you might as well figure on going all the way. That's why I suggest hitting the valve seals first.

Although I must admit, more than once I haven't taken my own advice, and just did the valves, with no ill effects.

If you do the valves, be sure you find a shop that installs the thin-wall bronze liners in the guides.