Discolored camshaft cap?

Hi folks,
I pulled my cylinder head cover today to check valve clearances. It all looks pretty good for being 30 years old but one of the camshaft caps has me puzzled. All are clean except the cap over the area of the #3/#4 cylinders. It looks like a caramel color like the oil has been baked on. Any ideas what might cause this?

Ah, I tried to post a pic with it but it was too big. I'll try and resize it.

How's the sparkplugs look? Signs of overheating?
Do the exhaust pipes look like they ran too lean?

Spark plugs all look good. Hard to tell on the exhaust as they're pretty badly discolored all the way across.

probably nothing,maybe pop cap off and check bearing for sign of getting hot

KZCM wrote:

Spark plugs all look good. Hard to tell on the exhaust as they're pretty badly discolored all the way across.

They generally get like that from the engine oil being over heated. Since it localized to one cap, I would venture to guess #4 exhaust valve had been run tight for a while at some point and the oil was in need of changing.

Also, I can tell by the top idler sprocket that it's a smog motor head. They'll generate more heat right in the bowl of the exhaust port because of the fresh air charge they get through the air port to continue the burning of exhaust gases in the port.

Dam tough motors I just took a head apart recently that had all 4 exhaust valves bent....but it ran.

You're right about it being a smog motor. I'm not too fond of that aspect. Anyway, when I checked the valve clearances, all were in the range between .051mm and .076mm except for the #4 exhaust which was at .102mm. So, you may be right that it was tight for awhile and the PO changed out the shim and left the others alone.

Not to start anything but 79-80 MKll's sold in Canada and Europe didn't have the EPA smog heads but did have that top idler. I've got one.

PLUMMEN wrote:

probably nothing,maybe pop cap off and check bearing for sign of getting hot

That sounds like a very good Idea to me, in case it has spun or otherwise lacking lube. Oil hole on bottom bearing to head alignment? Possibly the cap is on backwards, missing a dowlpin or in the wrong position? Should have #4 arrow facing forwards.

Does that mean I could track down a different cover and bypass / remove all the emmissions equipment?

I pulled the cap and checked it out. Good to go there with no signs of deterioration and everything's aligned correctly.

KZCM wrote:

Does that mean I could track down a different cover and bypass / remove all the emmissions equipment?

you can mount a 73-78 valve cover on there if you want,just plug the smog holes in head