The Stovebolt Site Forums The Shop Area Engine Shop intermittent blue smoke now

I previously posted smoking problem with 1960 235 engine under heading of "stumped". I appreciated the several suggestions offered by fellow bolts. Relevant information is: engine rebuilt by local machine shop for PO but never started. Many pieces missing. Confirmed rebuild with machine shop owner.
Scrounged/fabricated throttle linkage,
installed distributor, wired engine. Installed rebuilt Rochester carb and rebuilt fuel pump.When started, got the expected smoke, etc. After being run some, it still puffed blue smoke after warm. When idling, exhaust was constantly brown and did not smell right. Plugs were initially oily, but after driving some, changed to dry black powder. still had blue smoke in puffs.
Poured Sea Foam in all cylinders and let it set for two days. All plugs always identical appearance. Following previous bolt suggestion, performed ring seating procedure prescribed on Hastings web site. Perhaps not as much smoke but exhaust still not clean. Still brown at idle.
Installed Felpro umbrella valve stem seals. Observed that both valve guides and valves were new and fit perfectly.. At the same time, retorked head,reset timing, adjusted valves to specs. Set carb float level. Truck runs great, pulls good. Has 145 psi compression all cylinders. Do not have brown smoke now at idle. Blue smoke now is intermittent..hot or cold. Sometimes puffs blue quite bad, other times not at all with exhaust appearing normal. Plugs still accumulate black carbon powder that wipes off dry. No burned oil residue. Engine now has about 300 miles on it and has had the oil changed one time. Engine is obviously running rich but can't tell it by driving it. Carburetor was correct part according to O'reilys. I can buy another carb from a different source but my burning (no pun intended)question is: where is the intermittent blue smoke coming from?. I have tried to anticipate all questions and have tried to answer them so as not to waste your time.
meansam

One posibility is ring alignment. If the rings weren't correctly indexed the gaps might be lining up on occasion, allowing some oil to blow by.

Are you losing oil? How much did you add between oil changes? If you're not losing much oil I would say you're running a little rich,
Scott

I have added one quart, but did lose some oil while adjusting valves. I also had an oil filter (ferrel connection) come loose. Luckily I was just moving it a few feet down the curb when it came loose. Had to refil from that. I gave up on the ferrel fittings and replaced completely with hydraulic lines.
meansam

Blue smoke is going to be oil. You've only got about 300 miles on it, there's a good chance the rings aren't fully seated yet. I'd say most likely, you're getting oil past the rings, either from ring misalignment as mentioned earlier, or that they're not seated to the bores fully yet. Running rich will agrivate that problem due to the gas washing the oil from the cylinder walls.

If you are running a detergent multi viscocity oil, changing to a non-detergent straight viscocity lubricant will often make a huge difference in smoke emissions.

Blue smoke is oil, has nothing to do with carburetion. Rebuilt engines in my experience do not puff large amounts of blue every now and then. dIn fact, a rebuilt may not burn oil at all (I have seen that lots of times), or if it does, burns a little blue steadily until the rings fully seat. I think you have some oil leak down from a valve guide. Or they cracked a ring or ring land when they installed the pistons (that's easy to do if you are not careful). For my 2 cents, I would not do anything else and run it for about 1000 miles. If it has the same problem, start tearing down begining with the heads. When you pull the heads off, take a look for a vertical scratch or discoloration on a cylinder wall. Or take it back to the machine shop if they warranty their work.

I'd suggest giving it a little more break-in time, and monitor the oil consumption carefully. You might need to re-jet the carburetor a bit leaner, or install a power piston spring of a little lighter tension, to prevent the mixture from going full rich with a slight amount of load on the engine.

Rings rotate around the piston all the time, so the idea of the gaps aligning and causing oil consumption is a myth. They do align occasionally, but they don't stay that way long. If you're using a rail and expander type of oil ring, it's almost impossible to get the rail gaps lined up, unless the scraper rails were deliberately installed that way. Even then, both the compression ring and middle ring gaps would have to line up, and the gap would be a matter of only a few thousandths on a warmed-up engine.

If the smoke is still there at the 2500-mile mark, or oil consumption increases noticeably, a teardown might be in order.
Jerry

Meansam does this engine have a PCV system? I would check to see if the PCV valve is not sticking and drawing oil upinto the intake system. I also agree with HOTROD dirve it a little longer!!
good luck
DS

On the carb, make sure the gasket or spacer has the little notch cut out in it. There is a vacuum passage there that needs to be open for the power valve to work right.

Also, do you have power brakes or an automatic transmission with a vacuum modulator valve? One of those might be leaking into the engine.

I would like to know from Hotrod Lincoln how he knows that rings rotate around the pistons all the time. I ask this question respectfully, because I have never heard it before and I want to learn.

me too I did not think the rings rotated but the little problem this motor sounds to have is the carb is out of wack and the motor may not be broken in all the way, does your motor have a oil air breather or a paper air filter. Mine blew some smoke when I ran it early on cause the air filter full of oil was suckin a lot of oil and lets say it smoked pretty heavy. Them oil air filters need to have instruction manuals

Thanks for all the comments and suggestions. There is no pcv valve. no automatic transmission. No pwr brakes. I suspect any ring rotation is random, so any ring alignment would also be random.
The comment by 4onthefloor interests me. I remember seeing the notch, but could see no reason for its being so it may be installed such as to block vacuum into the pwr valve, which, I suppose would make it want to open. As I mentioned in my opening list of things that the engine did not run such as to suggest it is running rich. Only the plugs indicate it is running rich. I will check the notch. It must need to align with a hole or notch on the carburetor base.
meansam

At several of the schools I've attended, they have had engines with see-through cylinders, made of either tempered glass or quartz. I've used a delay-flash timing light, and watched the rings rotate. Perfect Circle Piston Ring Co. had a 216 stovebolt engine in their school several years ago (mid-50's) with a couple of glass cylinders installed. Really interesting to watch the flame travel, and color change while tinkering with mixture and timing!
Jerry

I always assumed that piston rings may move slightly from their original placement until they found their "groove", and that if they were turning it could be indicitive of a bent rod.

I recall on some 2 cycle engines I've worked on that there is a pin that the gap on the rings fit into to keep it from rotating. What gives with that? Dave

Small two cycle engines have an intake and exhaust port cut into the cylinder wall instead of valves and the pin is to keep the ends of the rings from getting around to that area where they would catch on the edge of the ports.
Richard

I keep learning all the time on this site, it's like an on going education. Thanks folks. Dave