[edbods]

You"ll also need to show us the cam journals when the shop calls to say they're trashed and u need a new head. Nope. They all look like that

Heh, when I rebuilt my head and looked at the cam caps the scoring looked quite awful, wish I took a photo. Was thinking that the head might've been screwed, but then just shrugged and pretty much just went 'we'll cross that bridge when it blows up'
About 12000 miles of hard driving later and it's still running like a champ.
Found a thread from 2004 talking about the same issue, it does seem like it's just 7M things. These are just the photos from that thread, but the caps and journals looked pretty much like what you see below.

 

[IdahoDoug]

Yep. I borrowed a bit of time on a lathe at a friend's shop and spun my cams. Made a little aluminum plate to hold sandpaper and just knocked the high spots off the cam bearing surfaces. Use a bright light and a dental pick to pop the bits of steel (shiny chips you can see embedded in that shot) out of the head and cap journals, then use a piece of correct size PVC pipe and fine sandpaper to knock off the remaining high spots. Now you've got oil clearance on the high side. Then lap the journal caps a bit to tighten up the oil clearance a bit. I used blue dye to keep track of my progress. It's documented in my "Father/son" thread. I've got great oil pressure and it runs like a top.

 

[edbods]

Could the cam journals/bearings be made of babbitt metal? Would explain why they look so torn up yet can still function perfectly.

 

[IdahoDoug]

Aluminum

 

[3p141592654]

The cam journals are indeed plated from the factory with some type of babbit material. It is what makes that strong sulfur smell from factory cams when the goop is still present. With the oil feed in the front and the long small journal to the back bearings you will see more wear on the rear bearings, and in bad cases the babbit will be completely gone. If the babbit is still there then I would leave it alone. It looks bad but that's true even with near new factory cams. As Doug notes, just lap the bearing caps to pull the bearing back into spec. Most of the wear occurs in the caps as that is where loading from the valve springs is greatest. You can test for the babbit by simply pressing your fingernail into it. If it leaves a dent, it's babbit, if it does nothing you are down to the cam journal metal.

 

[edbods]

I do remember a very distinct and strong smell that greatly upset my brother and his highly sensitive sniffer dog nose. The guy could honestly probably find work in an airport finding drugs on people.

 

[IdahoDoug]

The journals on the head are all one piece aluminum. Lapping the removable cap was simple and while not perfect, will bring them back into oil clearance. Wear on the cap occurs at the top of the "arch" which you then draw down slightly with the lapping. A little goes a long way, and yes I know it causes a slightly out of roundness but when you see it , measure things, study the angles, you'll realize it's worth doing to improve oil film.

 

[Snipe_sas]

Wow - will look forward to some pics! You"ll also need to show us the cam journals when the shop calls to say they're trashed and u need a new head. Nope. They all look like that. Just clean it up and reassemble.... so keep us in the loop while the shop works through things.

This^^ Beyond frustrating. The cam journals are fine, lol

 

[3p141592654]

to nitpick, the journal is the shaft part of the cam that rides in the bearing shell, which is the aluminum part machined into the head and cam bearing caps. For the cam bearings there is no bearing liner like there is for the crank and con-rod bearings, but the plated babitt substitutes for it.

Also eccentricity of the bearing is an engineered parameter. They are rarely designed to be perfect circles.

 

[IdahoDoug]

Yup - great illustration. Use machinists dye and lap them with an intent to get even cam pressure the length of the cams. Be gentle on the bolts each time you assemble as it's aluminum threads in the head. Strip one and you are done.