Marks on cams

[Carl]

I noticed that my cams have strange orangey marking on them. Given that the cam is rotating all the time I would have expected them to be shiny all the way around. What does this marking mean? Is this normal?

 

Carl.

 

Ps - it's a tt if that makes a difference

[devan]

Isnt it so you know where to position them when you change the cambelt.

[Carl]

Sorry I should make my explanation better. The markings are on the actual can lobes themselves. I am about to remove the cams in order to remove the head.

 

Edited March 16, 2010 by Carl (see edit history)

[RobSheffield]

Thats erm, not good.

[Carl]

If I were a guessing man Id say it's some sort of wear indicator rahter like the brass effect you get on the big ends when they are worn out but is that what it is. assuming that all should wear even why is the marking not all the way around?

Can anyone shed some light. the car has only done 80k.

 

Hers a picture of the pair of cams:-

 

carl

Edited March 16, 2010 by Carl (see edit history)

[RobSheffield]

Can it be rubbed off? Its either an oil stain or rust. The rest of the cam looks slightly rust, which isnt good.

 

Unless its a dodgy camera.

[Carl]

Can it be rubbed off? Its either an oil stain or rust. The rest of the cam looks slightly rust, which isnt good.

 

Unless its a dodgy camera.

 

It is not rust, and it doesnt feel worn in any way more than the shiny parts. it is on almost all the cam lobes. It literally is as it looks, just an orangy marking. doesnt look like a heat mark either.

its got me puzzled.

May i also say I have had no issues with the car either. the cams are not noisy at all when running.

 

i have not tried rubbing it off with something i must admit.

I thought generally, the cams looked pretty clean considering the cam covers have never been off before and this is without any cleaning up.

carl

[Digsy]

Looks a bit like the laquering you get underneath pistons.

 

The cam base circles do not touch the tappet, so the coating will not get rubbed off there. You can clearly see the start of the opening ramp in the first picture, where the colouration stops in almost a straight line across the cam lobe.

 

Looks like it might be heat related as in the second pic it looks worse on the exhaust side?

[Carl]

Looks a bit like the laquering you get underneath pistons.

 

The cam base circles do not touch the tappet, so the coating will not get rubbed off there. You can clearly see the start of the opening ramp in the first picture, where the colouration stops in almost a straight line across the cam lobe.

 

Looks like it might be heat related as in the second pic it looks worse on the exhaust side?

 

So this is all quite normal then. Now you mention it, it does look like a laquer coating. either way I assume nothing to worry about.

[Chris Wilson]

Perfectly normal on an old engine, it;s baked on oil varnish, probably worse on the much hotter running exhaust cam. As Digsy says, the tappet clearance means the back of the cam opposite the lobe shouldn't be rubbing the tappet. If it's polished all the way round the clearances would probably be zero and would indicate valve burning and a valve job and re-shimming required.

 

The carbonised oil on the cam caps and bolts is typical of cheap oil usage and irregular oil changes, I have seen them where you can dig the stuff out of the engine by the spoonful, so it's not TOO bad, but not a good sign, either. If you try flushing oil all that junk will get onto the oil pick-up strainer and cause worse trouble though!

Edited March 17, 2010 by Chris Wilson (see edit history)

[Carl]

Perfectly normal on an old engine, it;s baked on oil varnish, probably worse on the much hotter running exhaust cam. As Digsy says, the tappet clearance means the back of the cam opposite the lobe shouldn't be rubbing the tappet. If it's polished all the way round the clearances would probably be zero and would indicate valve burning and a valve job and re-shimming required.

 

The carbonised oil on the cam caps and bolts is typical of cheap oil usage and irregular oil changes, I have seen them where you can dig the stuff out of the engine by the spoonful, so it's not TOO bad, but not a good sign, either. If you try flushing oil all that junk will get onto the oil pick-up strainer and cause worse trouble though!

 

So whats the best option here.

I will clean up the head before it goes back on anyway but as for what I cannot see, are you saying best not to flush through and just carry on as is. May be better oil will break it down slowly?

 

Carl

[Chris Wilson]

Remove what you can with the head off (steam it if the valves are all coming out). You DO NOT want to flush it, best to leave well alone in the rest of the engine until it has a full rebuild.

[Carl]

Remove what you can with the head off (steam it if the valves are all coming out). You DO NOT want to flush it, best to leave well alone in the rest of the engine until it has a full rebuild.

 

Cheers Chris,

 

Valves are coming out so I will have it cleaned properly before reseating all the valves or replacing where nesesary.

I noticed some of the cam lobes are more shiny than others in the area of the orange marking so I assume also that some re-shimming will be in order. Ill be getting my feeler gauges out.

 

Carl