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I just got a 1993 CIvic Ex. When I got it, compression test indicated 210,210,0,210. I took the head off and saw that the cylinder with 0 compression had a burned valve. I installed new valves in that cylinder and put the head back on. New compression test shows 210,120,210,210. It smokes alot. I poured some oil in that cylinder because I thought maybe it was washed out "flooded" because the motors oil smelled like gas. THe compression rose to 240. What to do next?

 
Rep Power: 518

How long have you ran the engine? Has it been driven?

Did you change the oil yet? Do this. Any coolant that may have gotten in the crankcase when you lifted the head off can trash bearings in a hurry.

Oil in the cylinders should boost the compression, so the numbers are probably right for the situation.
If the engine hasn't been running long since you set the head on, there may be a lot of crap inside the exhaust to burn off. Plus the oil you just dumped in it.
If it runs on all 4 now, go drive it for a while and see if it clears up.

I did an engine in a car that had a blown head gasket, it had dumped a ton of antifreeze into the exhaust. Gallons of it, apparently.
I started flooring it at around 5 miles into the test drive. I thought things were great until I floored it and ran it to redline, it started blowing all that coolant out of the exhaust and looked like a smokescreen for a block behind me! It still was steaming for a long time even after the test drive, seems like it was a good half hour after I got back to the shop that it was still polluting. LOL


Stuck oil rings would also be suspect in a car that old.

HTH

 
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I just changed the oil with some 10w 40. I haven't driven it much, I let it idle for about an hour and the smoke has cleared up by about half. I was thinking a stuck ring too. The valves had alot of carbon on them. The car was driven b an elderly women so I don't think it was driven hard. I did get oil in the exhaust though. How long does it take to clear up? Any advice on a stuck piston ring? It runs perfect besides the smoke.

 
Rep Power: 518

Go drive it, and drive it hard. Get the exhaust hot all the way to the tailpipe. I would have run 5w20 in it and not be scared one bit.

Go drive it around several days normally after this. See what kind of oil consumption you have.

Do some research on Northstar stuck rings, see how GM tells to deal with it. Gotta make sure rings are suspect though, first, before attempting this.
Could be fine after driving it for a while, you know.

If you do the soak procedures that GM gives, you will be changing the oil again because that top end cleaner gets in the oil and that isn't great for bearings either.
Again, I'd use 5w20, and probably Mobil-1 or the semi-synthetic that goes in most of the cars now. Better quality base stocks than any 10w30 or 10w40 and can help clean the carbon from the inside out.
Some people will scream about the thicker oil must be better, but that isn't necessarily so.


If the rings are actually worn, replacement is the only thing that will fix it. Does the car have a ton of miles on it?

 
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The car has 191k on it. The other 3 cylinders had compression in the 200's, the cylinder with the burned valve had 120 after I replced the valves. If I put oil into the cylinder, the compression shoots right up to 210. But if I let it idel and smoke, the compression goes right back down to 120. I don't understand how only one of the cylinders gets worn more then the other 3. So Right now I am hoping its a stuck ring. I wouldn't think 120 psi would smoke as bad as it is anyway.

 
Rep Power: 518

So a compression check looks more like this: 210, 210, 120, 210?
And the low cylinder came up with oil?
(Assuming the valves are "right", valve job AND adjustment) That's rings.
Worn or stuck, can't tell from here, but the oil is coming up past the rings.

Probably has everything to do with the burned valve on that cylinder.

Maybe being constantly washed down with fuel caused accelerated ring wear.

Maybe low compression caused excessive carbon buildup.

Who knows....

 
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Yeah, I have driven the crap out of it, I put Marvel Mystery Oil in that cylinder. It smokes to the point of being pulled over. My other option is to buy another Z6 that has a blown head gasket. It had good compression. I could take the head off of my engine and put it on the new "used" engine. I'm just trying to get a cheap car together here. I'm pretty sure the other engines head is warped, and i'm homping the block isn't. Im getting the other engine for 75 bucks so if i'm lucky, I could puta 40.00 head gasket on it, put it in the car and drive it. Good idea?

 
Rep Power: 518

Blocks are hard to warp, but rings can collapse when overheated. They can lose their spring tension.
Good compression is a plus.

A compression test can't tell you about the oil control rings though.
They could be missing completely and still show good compression.

Why not pull your head and pan and re-ring it?

 
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rings, bearings and a head gasket are going to run around 250

 
Rep Power: 518

Hmmm....If the engine wasn't noisy, I might skip the bearings for the moment. Look them over while the rods are out and decide then?

Also, if it were mine......I wouldn't even hone the bores if the cyl's LOOK ok.... Just clean all the carbon out of the ring grooves really good before shoving new rings on it, and stuff em in.