Chipped valve
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Are you sure it's not just an extremely burned valve?
If a piece of the valve that large actually broke off (and presumably exited via the exhaust), you would be able to see mucho telltale marks in the piston crown and cylinder head.
If a piece of the valve that large actually broke off (and presumably exited via the exhaust), you would be able to see mucho telltale marks in the piston crown and cylinder head.
Steve
Elan S1 1963-Bourne bodied
Elan S3 1967 FHC pre airflow
Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
Elan S1 1963-Bourne bodied
Elan S3 1967 FHC pre airflow
Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
- bitsobrits
- Third Gear
- Posts: 420
- Joined: 27 Apr 2011
Check if the valve stem or head is bent, if you hit the piston you normally put a bend in it. Been their done that
A small bend can lead to exhaust gas leakage past the valve and seat. These hot gases can rapidly burn out the valve like you appear to have.
Clean the valve and check the face of the fracture with missing bit. If its a fracture that will be obvious versus a oxidation burnt surface.
Even a small leak due to wear and without hitting the piston ( or other valve) and bending the valve can lead to a valve burning out rapidly. Lean mixtures and over advanced ignition and loose exhaust stem clearances and poor conductivity valve guides can also contribute to or cause the problem especially in a race engine with constant full throttle high rev use.
cheers
Rohan
A small bend can lead to exhaust gas leakage past the valve and seat. These hot gases can rapidly burn out the valve like you appear to have.
Clean the valve and check the face of the fracture with missing bit. If its a fracture that will be obvious versus a oxidation burnt surface.
Even a small leak due to wear and without hitting the piston ( or other valve) and bending the valve can lead to a valve burning out rapidly. Lean mixtures and over advanced ignition and loose exhaust stem clearances and poor conductivity valve guides can also contribute to or cause the problem especially in a race engine with constant full throttle high rev use.
cheers
Rohan
-
rgh0 - Coveted Fifth Gear
- Posts: 8831
- Joined: 22 Sep 2003
seems I had no idea what a burnt valve could look like. googled it and found many valves looking like mine. Sure enough the "fracture surface" on mine didn't look like a fracture but indeed almost like a torch cut surface!
Valve measures straight and seat looks fine. Valve seems tight in guide. I don't believe I have lean running or advanced timing issues but will recheck when all is back together. maybe it's just time for a head rebuild? Any opinions on the below cylinder head photos?
number four cylinder with burnt valve:
number 1
number 2
number 3
Valve measures straight and seat looks fine. Valve seems tight in guide. I don't believe I have lean running or advanced timing issues but will recheck when all is back together. maybe it's just time for a head rebuild? Any opinions on the below cylinder head photos?
number four cylinder with burnt valve:
number 1
number 2
number 3
- mini64
- Second Gear
- Posts: 176
- Joined: 26 Aug 2005
Why is the spark plug in the #3 position so recessed? Just not tightened in?
- Bud English
- Coveted Fifth Gear
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- Joined: 05 Nov 2011
It looks like something small went through the cylinder with the failed exhaust valve from the dings in the cylinder head. This may have been a bit of the failed valve or it may have been something else that caused the valve to fail.
It may have been a bit of broken ring or an electrode off a spark plug or something small that came in the inlet. Worth a look around to see if you can find where it came from.
cheers
Rohan
It may have been a bit of broken ring or an electrode off a spark plug or something small that came in the inlet. Worth a look around to see if you can find where it came from.
cheers
Rohan
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rgh0 - Coveted Fifth Gear
- Posts: 8831
- Joined: 22 Sep 2003
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