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Burned out exhaust valves
- Thread starter 20975
- Start date
DrPaul
DrPaul
Burned exhaust valve
Looks like the "blow torch" effect. A piece of carbon dislodged from somewhere in the combustion chamber and lodged between the valve and seat. This prevented closure of the valve and the superhot exhaust gases simply cut a hole in it. Or, the valve stem seized in it's guide resulting in the same outcome.
Looks like the "blow torch" effect. A piece of carbon dislodged from somewhere in the combustion chamber and lodged between the valve and seat. This prevented closure of the valve and the superhot exhaust gases simply cut a hole in it. Or, the valve stem seized in it's guide resulting in the same outcome.
AntonLargiader
Active member
I was kind of hoping for a shot like the original one, but I think you can still see that the valve contact is running off the inside of the valve face. It should be more centered and probably wider (should be 1.4mm minimum).
jfremder
New member
What determines the width of the valve contact area?
Wear?
Original Valve Angle?
Valve Lash?
AntonLargiader
Active member
The original (factory) valve job, seat grinding and so forth. Then you have wear.
j-budimlya
Jim Bud
I'm not an expert, but it looks to me that there is a lot of carbon build up on the part of the valve that was not burnt. When I had my heads off, I did not have that much build up on the valves. I removed the heads to replace the head gaskets.
Anyone else think that this is a lot of build up?
Anyone else think that this is a lot of build up?
J
johnrobbo12
Guest
Looking at the pictures of the ÔÇÿburntÔÇÖ valve, I would say that if burnt means melted then that is not what has happened. The sharp edges and crystalline appearance (see photo #21)
indicates a piece of the valve head broke out. The rest of the seat looks good which adds weight to my theory because excess carbon build up and or tight tappets would cause the rim of the valve head to overheat all around itÔÇÖs circumference and there would be a ragged appearance to all of the valve head.
indicates a piece of the valve head broke out. The rest of the seat looks good which adds weight to my theory because excess carbon build up and or tight tappets would cause the rim of the valve head to overheat all around itÔÇÖs circumference and there would be a ragged appearance to all of the valve head.
