Smoking after overhaul

[Rulebreaker]

I took the truck to the machine shop today, and they changed the 2 seals on cylinder 2. Brought it back home put it back together, with a new PVC valve hooked to manifold vacuum, started it up and after it idled about 5 mins the smoke started to roll out the exhaust as bad if not worse than before. So I thought I would take it for a drive to see if it clears up going down the road, and the stupid thing wont go over 25 now. At about 20% throttle it falls on it's face. I rechecked compression and now they all read 150, which is 20 more, I checked timing, both ignition and cam, both look good. It's like I'm going backwards here. It ran great when I parked it. I really dont know what to think or do.

 

[Rulebreaker]

 

[Rulebreaker]

This is after about 250 miles total and about 125 miles after the cylinder 2 valve stem seals were changed. Cylinder 1 is on the left.

 

[Mark_88]

That looks a little burnt...maybe installed the wrong rings...hope the rebuild goes better the second time around...

 

[GentleRF]

Something I was taught from the time I started wrenching on small engines was to pay really close attention to which side of the ring goes toward the top of the piston. If the middle (second) ring is inverted, there will be smoke. You may also have bad seals on more than the one cylinder. Especially if you are using Teflon seals and the valve stems weren't deburred as part of the machine shop work.

 

[Rulebreaker]

The second cylinder definitely has cleared up after the valve steam seals were changed. The plug still looks a little coated but nothing like it was. What puzzles me is how much oil is on top of #one but the plug is very white, and the exhaust valve is a strange color. I personally think all the valve stem seals were leaking but that #2's were the worse and that the seal change cleaned that cylinder up. But I'd hate to replace them and then find out I was wrong. As far as rings go I stared at those rings for an hour before putting them on and I couldnt see what side to put up. They looked the same both sides. They had zero directions with them which I found real irritating. So do i pull the pistons out of her? RB

 

[Rulebreaker]

Something I was taught from the time I started wrenching on small engines was to pay really close attention to which side of the ring goes toward the top of the piston. If the middle (second) ring is inverted, there will be smoke. You may also have bad seals on more than the one cylinder. Especially if you are using Teflon seals and the valve stems weren't deburred as part of the machine shop work.

I met with the machine shop today and we decided to change the valve seals and the rings for round 2. He also showed me that the second ring has a top side. I did not know this and my overhaul book makes no mention of it. So I pulled the pistons and the only one up side down is cylinder #2. 3 out of 4 by shear luck aint bad! So lesson learned, now if I can just remember that for next time. RB

 

[HAPPY+RANGER+GUY]

lessons

...So lesson learned, now if I can just remember that for next time.

And many others will benefit from your experience as well!!!

Thanks for sharing this info.

 

[Mark_88]

Yes, thanks for the information...I was considering rebuilding my short block and that's something I would need when the time comes...if I do it myself, that is...I'd hate to stand over the shoulder of another guy watching to make sure they put them in the right way...lol

 

[Rulebreaker]

Talked with the machine shop today and they discovered the smoking gun. They sold me the wrong oil rings for the pistons they sold me. The center part of the oil ring is supposed to hold the top and bottom piece snug to the cylinder wall and the center piece is not tall enough to do that so basically it was like not having oil rings at all. Now I feel allot better knowing we found the problem, rather than this or that MIGHT be it. Being it was their mistake they are getting me the gaskets to put it back together again so I'm only out time and an oil change.

 

[GentleRF]

Good for you!

 

[tomw]

A little late to the party, but wth. I looked at the pics and thought there must be NO oil control. The pistons are not to have oil sitting on top of them. The exhaust valve that is white is running HOT, and will likely not last too long. Either the spring is weak, the lifter not letting the valve seat, or the valve seat is cruddy on the head or valve. It is not transferring heat to the head and is cooking.
The valve stem seals are effective at keeping oil out of the intake side, reducing the intake manifold vacuum ability to pull oil down the stem. Go fast, take your foot off the gas. You won't likely see smoking UNTIL you put your foot back in it. That is when the oil sucked past the seals will get fed to the combustion chamber. An engine at idle that is suddenly goosed that puts out a blue cloud is also showing signs of leaking seals. Same deal with vacuum at idle and the sudden goose.
I would check that the head bolts that are specified are "torque to yield" or 'regular'. If they are the former, you can only use them one time, and must replace the bolts when you put it back together. No point in cutting a corner now after all this work.
The PCV system has two 'ends'. One is fresh air fed from a filtered source, likely ahead of the carb/throttle body, that leads to the top of the cam cover. The other end is on the side of the block under the intake, where there is an elongated 'can' that sits on the side of the block. One end has a hose attached, that leads to the in-line PCV valve and then up the the underside of the intake after the throttle body, or to the intake on a carb'd engine. In other words, manifold vacuum.
The PCV valve will close at high vacuum, and open at lower vacuum levels to allow flow. It can get gummed up, and fail to open. That will lead to an engine covered in leaked oil in a lot of cases. The elongated can is an oil separator. Inside is coarse shavings of various materials that can handle heat and crankcase contents. The flow goes through the shavings or in some cases a labyrinth to separate liquid oil from the vapor. The oil will attach to the walls or shavings, and trickle back to the crankcase. Unless the drain is plugged, or the separator full of gunk. In which case, liquid oil can get fed back to the intake.
tom