Colouration of exhaust valves

[Dave Woodward]

While I have the engine out I noticed that the exhaust valves are noticeably different in colour, some remain quite dark whilst others are very pale. Can anybody offer an explanation?

[StuBaker]

Well, looks like it could be:
*a tad lean (the white one)
*slightly rich or (the dark one)
*valve seals leaking (the dark one)
I've looked for a colour chart but haven't found one, yet.
Check your spark plug colours to see if they match the valves, that will help a bit.
Do you have a BRA 289?
Are you running twin SU's on RV8 manifold? I THINK each carb feeds different cylinders each side. If they're not properly balanced it could leave some cylinders rich and some lean. Which will average out if you test at the exhaust.
You could maybe check by following back from valve to carbs?
Try using a 'Colourtune'. BUT on cylinders fed by each carb. ie 1 and 2 (see pic)
I'd be interested to know what you find, good luck,
Stu
ref: https://www.v8register.net/subpages/V8NOTE17.htm

[cobraboy]

That is not a Rover cylinder head.

[StuBaker]

Of course, sorry about that. Scrap that post then!! Hee Hee!!
Maybe valve guide seals then.
StuB

[peterc]

I certainly don’t disagree with Stu. White is weak mixture and dark is rich running. I assume you are running a quad carb on your Ford. So you need to check why there is a difference between one cylinder and another.
My concern would be that I had been told that the colour toning with the current newer ethanol fuels do not usually produce such positive colour distinctions albeit the conversation was around the exhaust system not the engine itself.
I think you must be running very weak on those that are pale and of course rather rich on those that are dark.
As Stu suggests check the valve seals for the reason of the black bits.
Peter C

[Dave Woodward]

I only run Shell VPower and so haven’t put anybody the new ethanol mix fuels in the Cobra.

I’ll not get a chance to check the valve seals before LMC23. Interestingly the other bank are all a nice pale brown colour so looks ok there. Can I expect any long term damage if two of the cylinders are running very lean? Temps etc?

Dave.

[Dave Woodward]

I only run Shell VPower and so haven’t put anybody the new ethanol mix fuels in the Cobra.

I’ll not get a chance to check the valve seals before LMC23. Interestingly the other bank are all a nice pale brown colour so looks ok there. Can I expect any long term damage if two of the cylinders are running very lean? Temps etc?

I have noticed a slight stutter (faintly audible) when cruising - not under acceleration. May be related.

Dave.

[peterc]

Are you happy that there is no air leak to those ports showing the ultra white look?
Peter C

[Dave Woodward]

Where are you thinking of Peter when you refer to air leaks?

[peterc]

Years ago and admittedly on a four cyl engine I had a leak across the inlet manifold gasket. Therefore air was being pulled in that had not gone through the carb. The individual cylinder ran hot and ultimately damaged a piston ring or two.
It happened on two occasions before the penny dropped that there must be a reason for breaking the rings on the same cylinder twice.
That was on a twin DCOE set up but I just wondered if it could apply to your inlet gasket. Eg a leak between inlet manifold and head.
Peter C