I will try and make this as short and detailed as possible. Knowledgeable help is very much appreciated. '96 spec JDM ITR motor. Stock internals. Just aftermarket exhaust. 125k miles. Never had an issue with the motor till now. Here are the details

Back in January #2 cylinder lost compression. Infact I lost all compression in that cylinder. I pulled the head to find a melted exhaust valve. The valve guide seemed fine w/ virtually little to no play and the valve seat looked great. I replaced and lapped a new valve in. The car ran great for about 3 months. Then the same issue came up. The car still ran but was underpowered and shook a lot.

Today I took the head off again and found the same valve melted but this time the melting was smaller. I have noticed a lot of carbon build up on the exhaust valves on cylinder #2 and #3, I don't know what would cause this if its a related issue.

My Question is what would cause my valve to melt. Bare in mind its the same cylinder and same valve as the first incident. Has anyone ran into this issue before and what was the solution to fixing this problem. I don't want to keep replacing a valve and head gasket every 3 months so a permanent fix would be greatly appreciated.

Please see the attached photos.

 

all that can come to my mind is the mixture in that cylinder chech stuff like injectors and stuff ..never seen something like that ...does the piston in that cylynder make contact with the valve...could be bad valve seat and it stays somewhat open when the combustion ignites

 

Great advice on the Injectors. I will have to get them cleaned and tested. So when I lapped the new valve in back in January no light came through the exhaust port and I put water on top of the valve seat and nothing leaked through to the port. So I'm guessing the valve seat is sealing properly. Its just weird that its the same valve. Even a dirty injector would maybe cause other valves in the same cylinder to have issues but it seems to be just this one. Keep the ideas coming.

 

Injectory spray pattern. The fuel isn't atomizing properly causing it to get way to hot and carbon build up. I would send you injectors out to get tested and cleaned.

 

You will want to check and make sure that cylinder is not lean as someone mentioned.

Also, lapping valves is not an acceptable repair and could have caused that valve to burn. Lapping damages the valve face which could cause it to leak. Lapping should only be done with an old valve that has had it's face resurfaced so it is concentric with the stem and then discarded after use.

 

The spark plug in the cylinder in question looks lean. So with the information I've gathered it looks like i have an injector issue. My plan is to send my injectors to get test and cleaned and then retested. That way I have data from before and after cleaning. If i notice significant difference in the data from one injector to the next I probably know that this is my issue. I plan to send my injectors off to http://www.witchhunter.com for 19 bucks /injector I can have this done.

If anyone has different ideas please let me know.

 

Burnt exhaust valve... Well valve clearance too tight on an exhaust valve can cause that.
An exhaust leak very close to the cylinder head can cause an exhaust valve to burn. From how it's been described to me, the leak, while allowing exhaust to leak out, will also suck in air. This cold air will cause exhaust valves to burn. Why, I still don't quite understand.
Carbon deposit on the valve face can cause a hot spot and cause the valve to burn. However, hot spots in the combustion chamber will often cause detonation or pre-ignition. All of your exhaust valves seem to be fairly white in the top picture, indicating possibly a lean mixture.
If lapping in valves is not an acceptable repair, then I know Honda master technicians that do improper repairs. Lapping a new valve in is basically the same as honing a scratched cylinder wall when putting in new rings. You're cleaning the surface of imperfections to create a good sealing surface.
How does the piston look in that cylinder? Have you cleaned it off and checked for any signs of damage? Have you checked the compression across the board?

 

All post in this are good. Your lucky the piston is still with you. Strike three could be bad. Problem is still with you don"t stop untill you find it. I think injector is possible ( must check)but more often when stock with header it may be heat. Did you take heat shieds off? Is timing with in specs? Hot and cold compression ck. Are you adding boster to fuel?

 

My motor is bone stock. No aftermarket header and no intake. Timing is dead on. I timed it with the light after the first incident. No booster in the fuel. I always use Premium from either Safeway, Chevron, or Shell. The only Mod is a Mugen Twin Loop Exhaust. I have not checked the compression in Cylinder #2 because currently its Zero. When I do get a new valve lapped in i'll be-sure to take the compression so I have some Baseline Data.

 

Do a compression test across all 4 cylinders at both cold & operating temperature (like spanky_1 said) after you do the repair. I would have said to do a complete compression test on the engine before the repair, but since you already have the cylinder head off that's not really a reasonable task. Make sure they are all above minimum spec & all within 28 PSI of each other (15% or less difference is even better).