Groove on Camshaft

[Spetz]

Hi everyone, One of my camshafts has a groove on it. It is where the camshaft bearing cap goes on. I've posted pics of the groove, and can feel it with my finger nail. Is this ok to run or is it a ticking time bomb? Also one of the lobes has discoloration but is smooth to the touch, can anyone tell me what it is? Engine is a 6A12 MIVEC Mitsubishi, so probably a bit over 20 years old. Has had a full rebuild though.

 

[Trav]

Usually one small groove is caused by some sort of contaminant that got past the filter, it may have been there for years. If the rest is smooth and the head and holder are smooth I wouldn't worry about it. The cam lobe looks like varnish but I have no idea why it would only effect that one unless there is a hole in the cover right above it that draws oil fumes right above it. Maybe an automotive machinist will chime in.

 

[cmhj]

Run it

 

[circuitsmith]

The groove probably came from a piece of grit left in the bearing after the rebuild. Cleanliness IS Godliness when rebuilding an engine. The discolored lobe looks like rust to me. This could happen if the engine sat a long time (months or more) between runs and all the oil came off the lobe. I don't think either is a significant issue.

 

[spasm3]

If the engine has been rebuilt, the groove may have been debris from inital startup. Chances are its been there a while and is not a problem. Since you are in there, i'd pull the cam and check the lifter under the discolored lobe. See how it looks in case its dirty, or worn out. I'd make sure oil flows through it and its not really loose or anything.

 

[ARCOgraphite]

You don't want a raised cusp on the groove. I agree with circuitsmith that it was prob some machined matl that circulated in. How does the saddle look? If ok leave alone, if not spin it and stone it then refinish the journal. Not mirror polish - some zig-zag oil carrying scruffs. Why is cam box apart? Clearance setting after wear-in? That is not looking like a "full rebuild"

 

[Spetz]

Thanks guys. The engine rebuild was in 2007 and the last time the car ran was 2009 I believe. It was stored until recently. I believe the valve stem seals hardened from time. After starting it for the first time it would blow clouds of oil smoke. After about 1-2 hours of running the smoke went away but it still puffs smoke after idling a while. I also had a look inside the intake manifold where the valves are and the intake has oil staining that wasn't there before I started it as I had taken the plugs out a spun the motor to prime + dropped a bit of oil down the spark plug hole. I assume that the valve stem seals hardened/dried and after a couple of hours running they must've gotten softer if that's possible? Since the timing belt is almost a decade old I am in the midst of swapping that and thought it a good opportunity to change the stem seals too

 

[funflyer]

I think I'd be more concerned with the corrosion pits on the cam lobes, if that's what I'm seeing.

 

[46Harry]

The slight groove shouldn't be a problem, but the rust and pitting on one of the cam lobes could become a major problem in the not to distant future.

 

[Ohle_Manezzini]

Is it pitting corrosion? If it is, change the shaft now or it will self destruct in that area, spreading debries all over the engine starting an ugly domino effect. Did this engine see frequent use or was underused, since it was stored sometime in its life... lack of use make way to corrosion.

 

[Trav]

If that's rust I still cant figure out why only on that lobe, will it clean off with carb cleaner?. Is there pitting on the lobes? The photo isn't clear enough to see 100%

 

[Spetz]

Hi guys, The corrosion on one of the cam lobes is smooth to the touch, so besides the the color it is completely fine. On the sides of it there is like a rust grease or something that must've cleaned off the lobes from starting it. I've spoken to a cam specialist and I am taking it in to be check by him so he'll tell me whether it can be polished out or whether I need a new cam