The Stovebolt Site Forums The Shop Area Engine Shop Dear God...THE SMOKE IS BACK!!!

Let me first remind yall that the smoke had subsided for a while, two nights in a row. My oil pan gasket was leaking (a new one, we just didn't put it on right) and so i changed it out on Friday night. As you all know you must first drain the oil through the pan plug. The oil that came out was solid black and there was only about half a quart total although that oil only had 40 miles on it! So, i filled it up with 5 fresh quarts of oil after the gasket change (it's on right this time) and turned him over. Ran fine, choked and gave gas to get running good (32 degrees right now) and after running for about a minute, little puffs of smoke started coming out the tail pipe. I gave it gas and it started the raging smokescreen i had the first time i ran it! I don't know where i went wrong! My compression test (90-90-100-110-100-100) means my rings are good (i think) and i don't know what to do now. All it took was an oil change and it started again, I am in a raging state of depression.

Let's see here. You have a late 6, still 250 per your gallery submission? You're putting great clouds of smoke from the exhaust, and losing oil out of the pan. Somewhere you're getting oil into the combustion chamber. I haven't had one of these late 6s for about 15 years so I don't remember the details externally, but in the chamber, it could only be coming from valve guides of rings. Your compression test was ok, so your rings should be fine. Have you pulled your plugs out yet? How do they compare? All a bit wet and oily or 5 tan with one black? That would be a big step trying to trace to the source. Check that and go from there.

Devin

Did you respond to the question of whether you had an automatic trans or manual?
I had a car once with a pinhole in the diaphragm of the transmission modulator valve.
The engine would emit horrendous clouds of white smoke whenever it got a sip of fluid.
Before a friendly mechanic clued me in to what was happening, I thought I was in for a total engine rebuild.
A new valve cost about $12 at the time, and it took 5 minutes to install. Problem solved.

If you lost 4+ quarts of oil in 40 miles and what was left was "solid black" I would imagine you have a pretty serious problem with oil getting into the combustion chambers and then the combustion being blown past the rings... the cause of the black oil (?). Chances are your compression test is false because of oil in the cylinders sealing bad rings.

I'd start by pulling the plugs and seeing what they have to say about the problem, but I wouldn't expect any good news.

if there was only about half a quart oil left in it you may have damaged the internals for lack of oil.From what I'm reading it quit smokin' for a bit? There was no oil left to burn....

Spark plugs are all oily, black and crusty.

Could the fuel pump be leaking fuel into the oil pan? I haven't seen it on a truck but have on equipment and it turns the oil to about the viscosity of WD40. With the oil that thin, it seeps past everything and does exactly what you describe.

I don't know, the smoke smells more like gasoline now. It used to smell like oil.

I don't know for sure, but your compression readings seem low to me. I don't know the spec, but I would have thought that 120 - 140 (160 would be great would be appropriate for a re-build. You could try a "leakdown" test in each cylinder to determine if that may be the cause.

See my suggestion on your first post. I think you have a boat anchor for an engine,
Scott

How much would it cost for me to have a pro do a leakdown test for me?

Not sure, call around for a quote. I would shop around for a good used engine (one that you can hear run first) and go that route. May even get a 292 for cheap!
Scott

There's one that colletesbro has down in swap meet. Can't the 292 hook up to my 3 on the tree tranny? Also, could i use my same radiator and manifold, or are they different?

Contact Brian (Colletesbro), he's a good guy. I met him a couple of years ago. He may have everything that goes to the 292. Not sure about the interchangability between the two. I know the trans. stuff will bolt up though. Good luck and tell Brian I sent you,
Scott

Take it out behind the barn and put it out of its misery.

why not just rebuild it? it sounds like it needs it to me.
the remaining oil was black because when the oil gets real low
it also gets real hot the oil helps cool the engine but one
quart will over heat. i suspect it quit smoking because it
didnt have enough oil to get to the rings.

You may have to choose between finding a running engine or a total rebuild. I think the 292 option is a good one, but there is most likely an engine in your area that is just like yours and running. A direct swap is probably the cheapest way to go if the replacement is a good one. If you find one do a compression check on the candidate before you commit to it.

Oil rings can be shot & an engine can still have good compression. Check the simple things like a bad fuel pump or PCV system sucking oil out. How about blowby? Run the engine with the PCV valve out & see if there is smoke comeing out the hole. If so the rings are surely shot. If you have oil in the PCV hose it would indicate oil being sucked through it. A broken shield inside the valve cover can cause this. If you determine the engine is shot another 250 is easy to put in. The 292 fits but takes some modifications.

Never removed an engine. The 292 i know requires new engine mounts, but i hear it bolts to the 3 on the tree transmission. Does anyone know if the manifold is the same and if i need a bigger radiator? Thanks

You cooling system, if in good shape will be enough. You will have to modify the right motor mount and the pulley alignment maybe a little different. You exhaust pipe will need to be changed from the muffler to the manifold, 292's are about 2" taller so your pipe will be short, plus 292's use bigger diameter pipe. The fuel line will need to be changed a little, 292 fuel pumps are in the center of the right side where as 250's are towards the front of the engine. Joe

The compression does sound low for that engine and there is too big a difference between the high an low cylinders.

Unless the leak was so excessive that you lost four quarts of oil in 40 miles I would say that the rings are weak at best and you probably have worn guides and a few valves that aren't sealing as well as they could.

I'd do a leak down test to be sure of the rings and valves.

That will show you where the problems are and you can go from there.

Thing is the head is brand spanking new, so i guess it must be the rings. I just don't understand what i did wrong. I honed out the cylinders. What kind of mistake could i have made causing the rings not to seat?

How did you clean the cylinders after the hone job? The only effective way is lots of hot, soapy water and a scrub brush, and do it repeatedly. I use Tide, a bucket of almost-boiling water, and a round toilet brush. Scrub, rinse, repeat. Do it again. And again. Hone grit is very difficult to remove from the cylinders, and if it's not removed, it wears the rings out almost immediately.

You've done a half-azzed rebuild, and you got the results some of us oldtimers predicted. Now, pull the engine out of the truck and do it right this time.
Jerry

Good advice, and after you have done that you should take a white cloth soaked in the highest detergent oil you can get and scrub the cylinders. You should do this until the last cloth comes out clean. It is time consuming to do this, but it is about the only way to remove all traces of the honing dust.

I didn't see if you got the block bored out and got corresponding rings. If you only honed the cylinders and used stock sized rings, you could reasonably expect excessive oil consumption.

But Donsz, if honing does not bore the cylinders, and i honed it right (hypothetically speaking), why would standard size rings cause massive oil consumption?

I just cleaned the cylinders with rubbing alcohol, so it's possibly the problem. At least it's worth checking out before i buy another engine or get it bored.

Oh, and Hotrod, if i do decide to take the chance and go back into the engine, i will plastigauge the journal clearances

I learned how to clean honed cylinders the hard way, too. On a 2,500-mile trip from California to Tennessee with a fresh re-ring job, the engine got to the point it would use 3 quarts of oil to a tank of gas. When I tore the engine down again the rings were worn to less than half their original thickness. I had scrubbed the cylinder walls with clean white rags and lacquer thinner until they came out as clean as they went in, and that still was not sufficient.

Good luck!
Jerry

Last time I saw something like this happen was on a 292 in a Chevy bus a guy did an in frame overhaul on. He didn't take the ridge out of the top of the cylinder, said it was fine. When he started the bus, they couldn't use it because it looked like a mosquito fogger going down the road. He broke the rings and rings landings on the piston when it started up.

Was there a ridge, at the top, and did it get cut out? Did some rings get broken while putting the pistons in? My bet is broken rings on start up or installation.

Let us know what you find.

Alrighty then, only had a half day of school today and i got bored. So me and my buddy, knowing not about the condition of the rings, said what the hell...45 minutes later... we got the head off. Any suggestions on what to check for in the case of bad rings. My buddy is set on thinking it's not the rings, although im not so sure. He pointed out that there was a lot of oil gathered on the top of the block near where oil shoots up to the valves. He thinks the head gasket might not have sealed right therefore letting oil drip into the firing chamber. I think it's the rings. Here's a change though, this time i got...PICTURES!!! It's not like being right there but it's better than me describing it. Take a look and tell me what you think, feel free to ask any questions. Thanks guys.

My Photo Bucket- http://s101.photobucket.com/albums/m66/prestonmallard/

It is a little bit hard to tell by the pictures, but to me it looks like you might not have taken the ridge out. If you didn't, it is quite possible you may have broken the rings and possibly the ring land. The crosshatch doesn't look quite right either, although again, it is a little hard to tell by pictures.

Those Chevy motors usually have quite a bit of taper and if you don't take the ridge out you can easily break the new rings. That is about the only thing I would think of by looking at the pictures.

If you didn't take the ridge out, I would suggest removing the pan and knocking the pistons out to see what is going on.


That is a nice old Chevy pickup, it will all be worth it when you get this straightened out.

Look in each cylinder, top to bottom for any sign of a scratch in the wall. You will need to turn the engine so each piston is at the bottom. A broken ring should leave some type of line or mark.

What kind of rings did you put in it?

I once ringed a 318 Dodge with 100,000 miles, done just what you did, honed it out and replaced the rings. I used cast iron rings because they were cheap, problem was the cylinder walls were still semi smooth and the rings never seated. I was using oil like mad, but it wasn't smoking like a fog machine. After two weeks if trying to get them seated, I pulled the engine and replaced the cast iron rings with Moly rings. They seated with in a mile or two and ran for another 100,000. The cast rings looked just like they did when I pulled them out, only polished to a shine on the edges.

Joe

I should have explained my comment regarding honing vs boring. I assumed that the engine has some miles on it. Most likely the bore is worn a bit, so honing would only expand the "wear" and not really remedy any significant issues with the cylinder bore. By putting in standard size rings, there may very likely be an increased clearance between the rings and cylinder wall. If the cylinder bores weren't too bad a hone only treatment shouldn't cause as much oil burning as you are experiencing. My experience with honing only and standard size ring replacement, is that it can work "OK," but is usually a short-term solution. I wouldn't be surprised if a ring broke upon installation, since this is a fairly catastrophic symptom. However, it may be difficult to determine, because removing a piston can easily break a ring upon exit.

I agree with Donsz, that is why you can buy pistons that are 30, 40 and even 60 over for boring. Not sure if they are available for the engine you have.

I'm seeing a lot of serious misconceptions about cylinder prep and ring seating here, most of them "old mechanics' tales". That's the wrench jockey's version of an old wives' tale. Somebody who used to be a mechanic, or knew somebody who heard it from somebody else, starts repeating "facts" that just ain't so, and don't even make good nonsense.

Honing- - - - -that's a procedure done after boring, to remove the spiral groove left by the carbide cutter bit. It's done with a rigid-stone setup, and actually removes a couple of thousandths or more of cylinder material. It requires a thorough cleanup with hot, soapy water and a scrub brush, then repeated rinsing to get all traces of hone grit out of the block. This is best done with a totally disassembled engine- - -a bare block.

Glaze breaking- - - -done with various types of flexible-hone setups, either with three spring-loaded stones, or with a "dingleberry" hone consisting of dozens of ball-shaped pieces of grit on individual flexible stalks. Either way, it prepares the cylinder wall for a quick wear-in of a new ring set without reboring the cylinder. Virtually no material is removed by glaze breaking- - - -the surface of the cylinder just gets a crosshatch pattern without any diameter change. See above for cleanup procedures. The grit MUST be totally removed or the new rings wear out immediately.

Cylinder taper- - - - -this is wear that happens naturally over thousands of miles from the scuffing action of the rings. Practically all the taper in a worn engine happens in the first inch of ring travel. Even very high-mileage engines will show almost no taper wear from 2" below the top of the block to the bottom of the ring travel. Taper wear should not exceed .005" (5 thousandths) or the re-ring job will have a very short life due to ring flexing as the ring attempts to maintain contact with the tapered cylinder and it loses its springiness quickly.

Ring ridge- - - - -Unworn area at the top of the block from the rings not going all the way to the top. If a piston is forced out past a ridge, rings, or sometimes piston ring lands will be broken. If an engine has enough ring ridge to stop the piston from coming out of the cylinder easily, rebore the engine. You've got too much taper wear for a re-ring job. There are special reamers to remove the ridge if necessary. Always remove any ridge before installing new rings. A new ring will hit the ridge, and break the ring or the piston.

At 2,500 RPM, the rings in a taper-worn cylinder are trying to change diameter 5,000 times a minute to maintain cylinder wall contact. Reboring removes the taper, and allows rings to do their job for a much longer time without wearing out from metal fatigue.
Jerry

I agree with everything you said except I don't think you have to rebore with only .005 taper. As I said in a previous post, I have known professional mechanics that put rings in an engine with .030 taper and I would not do it but he knew what he had and drove accordingly. If you know you have something borderline or past and use it carefully, you can get by. Myself, I would rebore anything past .012, no matter how I used it.

There is something definitely wrong with this engine, but I don't know what it is.

I respect your belief that an engine should be rebored with .005 taper. It is probably correct, but there are other opinions. It is so easy on an internet forum to offend when that is not your intention at all. Please don't think I had that intention.

I tend to err on the side of caution, particularly when my profit margin is on the line. Back when a re-ring job was pretty common practice, there were plenty of other shops that didn't have a problem with installing rings in some pretty badly-tapered cylinders, or even a few that would rebore one hole to correct a scored cylinder. Most of them catered to the used car lot trade, so the salesman could claim his latest lemon had a "rebuilt' engine. I always went for longevity, as I found the customer would tolerate a bigger bill if he could be sure the job had a better chance of lasting a long time. Dad had a saying we tried to live up to- - - -"You can shear a sheep many times- - - -you can only skin him once!" One cut-rate job that ran the customer away was not worth it, because then we would have to find another pigeon.

Doing ring jobs without reboring are a thing of the past, because rings and blocks wear at about the same rate these days, and by the time the rings wear out, the block is beyond the point it will accept another set of rings without a rebore and new pistons. When a set of soft cast rings usually wore out at around 20,000 miles, we could do one or possibly two re-ring jobs before it was necessary to bore the engine. The first rebuild isn't necessary before the 200,000 mile mark on lots of engines, so modern technology and materials has just about eliminated rebuilds anyhow!
Jerry

The cross hatch in the photos looks to be at the wrong angle. Also, it looks like the ridge is still present. My guestimation is the rings are broken and acting like little pumps pushing oil into the combustion chamber.

It looks like the block has to come out at this point. My suggestion is to search craigslist.com or car-part.com for a running 250 and swap it in if you are low on cash. Otherwise, a good rebuild will cost you a minimum of $1500, more with a dyno run.

The good thing with the 250 is it has the same bolt pattern as the rest of the late 6's and the V8's. They are also plentiful, been in everything from pickups to vans to cars to boats to generators.

Scott

The guy that adjusted my valves came by today to check it out. He could move the pistons a little bit and said, and i quote,"Got too much play in ya dadgum rings, mmmhmmmm. Gonna have to be bored out. What's weird is i cant catch my fingernail on the ridge thats supossed to form up near the top. Don't worry, i'll bring the micrometer tommorrow just to make sure. I got a cousin that runs a machine shop down on Bay Street. Cost bout $40 a cylinder for boring and new piston heads'll be bout $20 a piece. We'll undo the u-joint, i got a lift and a turning stand you can use. We'll go ahead n' take out the crank and mic it too, see if ya wore down the journals, but usually you'd have heard a clicking from the engine if ya did that. I know it's scary, but it won't be that expensive." So right now i'm doing a rebuild. Not necesarily because i want to, but because my dad does. And to think i was concerned about throwing a rod... :mad:

I have read most of the entire post. A couple of things come to mind. 1.) what kind of rings did you use. Chrome rings are hard to ceat in and may take a few hundread miles of hard running for this to happen. Cast iron rings would be my choice.
2.) taper wear in the cylinder bore should be checked. I however do not remember how much is acceptable.
3.) did you check how the compression rings fit into the cylinder bore befoe they were instaled on the pistons. There is a magic measurment for the gap in the ring which is acceptable before installing them on the piston.
4.) a sloppy fit of the piston in the bore ( moving the piston side to side ) is not good.
5.) before you do anything more it would be worth your money to get a seasoned mechanic invole. Your truck looks like it's worth the extra $$$$ spent. Best wishes.