LS1 blowing lots of white/blue smoke. I did a leakdown test - First cylinder showing 40% plus on the leak tester. Second cylinder showing 100% loss.

Put in my cheap borescope(sorry for the poor resolution). Saw a small bit of metal lodged between the piston and cylinder wall. I know its a bit of a ring! Just want my worst fears confirmed.

Cheers,
Greg

 

That doesn't look like a ring to me. And the top of the piston looks really beat up, like something has been caught in there for awhile. I mean, you're obviously going to have to pull the heads anyway ( actually the whole engine, unfortunately ), so do that and report your findings. Best I can tell you.

 

I agree that’s not ring debris. If it was, the dome would be chipped/missing around the edge somewhere. Looks foreign to me. It has beat the dome up, as LS1 noted. Either way, pull the engine and prepare for a rebuild, or start shopping for another.

 

If its not part of a ring, then I'm not sure what it is. I've had the engine for a while, but its mostly been sitting in the garage while I've been finishing the car. Had it running for no more than 10 times, and then not for long. Maybe 20 mins max. each time.

All I've done to it is replace the valve stem seals as it was smoking randomly. But recently, it started running roughly, and then it started smoking continuously.

Head is coming off. Will update on what I find.

Cheers,
Greg

 

So I finally got the head off. Those angled bolts on the outside of the head were a nightmare trying to get them out. When I finally did get them loose (using a wobble bar extension), the one at the rear corner was hitting the side of the firewall when I tried to remove it. I had to loosen the engine mounts and use a jack to raise one side of the engine so I could get it out.

Once I removed the head, I could see the bit of metal stuck between the piston and cylinder wall on cylinder 5. I used a toothpick to remove it. As you can see from the photo, it is just a small piece of fine gold wire. It didn't seem to damage the cylinder at all. Not sure where it came from or how it got there?

Anyway, back to the original problem - the smoking. I've attached some photos of the underside of the head showing the valves. The inlet valves all seem to be level with th head. However, with the exhaust valves they all seem to be a little proud from the surface. You can see the ridge around them. Is this nornal ? (I recall with cylinder 5, when I was doing the leakdown test, I applied compressed air into the cylinder, and I remember one of the valves jumped up as if it had been stuck in the guide - this was after I had loosened the rocker arms so they weren't holding it down.). So this makes me think some of the valves aren't sealing properly?? There is a fair bit of carbon buildup on the head underside which I expected since this motor has done around 190,000kms (according to the guy I bought it from). Maybe the carbon buildup around the valves are causing them to stick ?

With the cylinders, there are a couple of things I noted. Firstly, there is some carbon buildup on the top of the pistons (again, expected). However, the buildup on piston 7 is of a different color to the rest. Ayn idea why this is the case? Secondly, there are some marking around the top of the cylinder and towards the bottom. I assume these are rust marks as the engine was idle for some time, hence probably some rust built up here. The walls still seem fairly smooth when I run my fingers over them. So is this a problem?

Next steps:
1. Remove the other head and get both heads reconditioned - remove the valves, decarbonise and clean the heads, replace any bent valves, check the valve guide, remachine the valve openings if necessary.
2. I'm not sure at this stage what to do with the cylinders/pistons. I really don't want to remove the block if I can help it. My options are:
a. Do nothing and hope its ok.
b. Remove the pistons, hone the cylinders and replace the rings
c. Remove the block, get the cylinders rebored and fit oversized piston rings

Advise appreciated,
Greg

 

Here is the view of the underside of the head and a close up of the valves for cylinder 5

 

View of the cylinders and cylinder 5 'rust' marks

 

You could probably get away with a light hone and rings.

If the valve was hanging up for any reason you could potentially have an issue. It wouldn't hurt to have a machine shop look them over and check the guide clearance. Perhaps just some debris was causing it to stick.

The tops don't need to be the same between the intake and the exhaust. What matters is the measurement under the retainer to the spring pocket. Some times the Exhaust or the intake may be slightly taller at the tip due to how they are manufactured and the way the valve face is cut. what matters is the install height for the spring so that you get the proper pressure recomended by the manufacture. As long as the same sets look fairly even on that bank you should be ok. If one is noticeably higher or lower that indicates an issue.