question Cylinder Head

[AndyB]

Having just removed the cylinder head, I thought I would ask the question why is just one of the valves a light brown colour whils all the others have a light carbon coating?

[Caddy]

I've got a couple of questions:

 

1. Is it off a running engine? If so how was the engine running?

 

2. Is the valve in question an exhaust or intake valve?

 

If the head was off a runner, and it's an exhaust valve, it may not have been seating properly and burnt out (the differantiation in colour showing up the heat damage).

 

 

Note: This is a wild stab in the dark.......

[GeePig]

I agree, it is time to pop those valves out and check how clear the oprts are..

 

Is it just me, or do cylinders 2 and 5 appear more carboned? I assume this has a single carb?

 

Trevor

[monty2]

With plug the rule is if they have a brownish colour it means good mixture, couldn't be better. Not sure if this counts for valves too, but if so you would like to have them all nice this brownish color as sign of healthy engine

[Pete Ashby]

I'm afraid without looking at the engine in it's entirety ie cylinder bores, pistons,rings, inlet manifold face and block face it really is not possible to be certain what the cause could be as it could be ware or damage to any one or any combination of these components causing the apparent colour difference.

 

Pete

[Big ray]

I've got a couple of questions:

 

1. Is it off a running engine? If so how was the engine running?

 

2. Is the valve in question an exhaust or intake valve?

 

If the head was off a runner, and it's an exhaust valve, it may not have been seating properly and burnt out (the differantiation in colour showing up the heat damage).

 

 

Note: This is a wild stab in the dark.......

 

I suspect that this is the most likely cause, heat passing the valve will generate considerable heat.

[Caddy]

Ray,

 

That was the thought, but a Pete said there are too many variables to say for certain.

 

I recon the best place to start with the head off is to check the head for damage, remove all the valves, check them and the seats, lap / re face if needed. Also would need to check piston ring gaps and cylinder bore wear.......

[rampant rivet]

Hi Andy

Have my head off as well and all my exhaust valves have that light colouration and on close inspection the valve faces and seats are all pitted and could not of been a good seal, I am off to a machine shop tomo to get them refaced I am also going to have the exhaust manifold face skimmed as well because this has suffered over the years, will post a few pics on my blog tomo,

 

Cheers Jeremy.

Edited April 22, 2013 by rampant rivet

[rampant rivet]

Have taken my head and valves to a machine shop today to have the valves reground as well as the seats they all needed sorting even the inlets, I am also having the exhaust gasket face milled as its suffered from heat damage.