First off, an explanation of the problem.
Over time, gunk, junk and whatever else built up a bond and galled the bolt and the Cam retainer together. Through the normal removal process, the fasteners wouldn't budge and if they did move, it felt like I was going to snap the bolt off in the cylinder head.
I searched here on NICO and came across a thread where the guy had actually BENT a Cam retainer or two while in the process of removing the same bolts I was having a hard time with. I approached it gingerly at first to make sure that I was going to be able to remove the bolts and not turn my cylinder head into scrap aluminum.
First off, I doused the retainers and bolts with liberal amounts of liquid wrench and let it sit/soak for an hour until attempting to force one of bolts loose from the retainer cap. I found smacking the ratchet end, loosening the bolt just a 1/8 turn at a time, the cap was beginning to rise with it.
I got the bright idea to use a deep thin-wall socket to hammer on the cap, using the hardened washer under the bolt so I didn't end up destroying the cam retainer. I used just enough hammer to force it back down to the Cyl head surface.
Each time I would do this, the retainer bolt would get easier and easier to turn. I would take turns loosening the upper and lower bolts so the cap torque would be released as even as possible for what I was doing. Now, if you do this yourself, be careful when the bolt gets closer to the end of the threads because if you continue hammering on the cap you're also forcing the bolt against the threads in the head. It's not a big deal when you first get started, but once the bolt is about 1/4 way from being all the way out, it's best to just spin out the bolt and not bugger up your threads.
About now, you have a cam retainer in your hand with one or two bolts securely stuck in it. Using the same method with the socket and hammer, I then move the cap to the anvil side of my bench vice and continued to lightly to moderately tap on the retainer evenly on both sides.
Continue this until the bolts are about flush with the bottom side of the retainer.
At this point, if you get a good grip on the cap with the aide of a rag or nice mechanics gloves, you should be able to use a cordless drill, or the like to spin the bolt free. If this doesn't work and the bolt is still stuck, don't forget to apply more liquid wrench or equivalent.
Once the bolt(s) is(are) out, you'll see the crud that was preventing the easy removal.
The deposits wouldn't come off easily with a rag and I didn't have time to soak them in a chemical dip, so I did the next best thing. I cut several 30mm strips of 220grit wet/dry sandpaper and used a cordless drill to spin the bolt while the sandpaper did it's job on the deposits.
They came out pretty nice. Don't forget to hit them quick with some brake cleaner or equivalent because you do not want any of the granules from the sandpaper finding their way into your motor!
Next is to clean out the bores of the Cam retainers. For this, I used the newly cleaned bolts and the cordless drill again, using the washer as a buffer again to prevent marring the cap with the 10mm bit. I used motor oil as the lubricant in this and brake cleaner to rinse away the corrosion. Orange lid is the motor oil!
The first time you put the cleaned and oiled bolt back into the still dirty cap, it may not go in all the way. In this case, just use your drill and spin it as much as you can then take the bolt back out. It will be coated with the crap that was inside the bore of the cam retainer hole. Rinse out the retainer hole and the bolt. Re-coat with oil and repeat this process until the bolt is completely free to spin in the cam retainer cap. This is critical because any binding or crap that still exists will prevent you from properly torquing the retainer caps. The RB motors use very light torque specs (6 - 8ft lbs.) so having no binding will ensure a proper torque.
Once you are satisfied with the clearances, it's a good idea to clean out the threads for the retainer bolts.
I didn't have a M6-P1.0 bottoming tap, so I used a standard cutting tap. Don't forget to lubricate the tap lightly (you're only chasing the threads) as it will help retain any crud the tap cleans from the threads. You don't want aluminum shavings in your cyl head either...
Also, make sure the retainer cap, both bolts and the cam is liberally coated in motor oil before slapping it all back together! Torquing it dry 'could' be a bad thing, and it's in the service manual...
So, repeat this about eleventy-billion times and you'll eventually be done! If you were careful and meticulous with cleaning the parts, you should have no problems getting the cams back where they belong for miles to come...
I am not a professional, just a guy with a garage and empty pockets... If you have an issue with a procedure I described here, PM me and if the concern warrants it, please post the correct way with specifics!
Thanks for reading. Have to get up for work in 4hrs...
Dan