A quick squirt of brake fluid, to remove any oil residue and a couple dabs of enamel paint on the sprocket and chain, next to each other, will help at reassemble time.
Now you can finish removing the camshaft sprocket bolt. Keep it with the fuel pump eccentric. Look at the camshaft sprocket BEFORE removing it. Note the three little holes in the center of the sprocket, and the outer edge of the sprocket. Just make a reference as to which one was fitted to the locating dowel of the cam. Whew, now you can remove that sprocket. Finally!
Head bolts: remove from the outer edges, working toward the middle, in a circular pattern. Front two first, rear two, then the next two in the front... (See figure 2)
Now the head should just pop off, right? Well, pretty rare. I use my rubber mallet to keep hitting the sides. Other folks like using a long bar down into one of the ports to "lift" the head to break the seal. What every works.
Once the head is loose, remove it slowly. I like leaving the head gasket in one piece to inspecting it. Place the head down on its side. Valves will be open, so use caution.
PIPE CLEANER: make a knot in one end, and stick the other end down into the oil passage hole. You'll find that hole near the dipstick. Idea is to keep junk out of it.
Inspect the Head
When replacing a head gasket, always check the head AND block for straightness. If I see more than 0.003" warpage on a head, I like to have them surfaced.
TIP: Often overlooked: check both TOP and bottom on the cylinder head for warpage. Ditto on the manifold side. Same for the intake manifold. If the surface is not flat you'll have a hard time getting the intake manifold's water passages sealed.
3M makes some great gasket cleaners that do an excellent job of prepping the block and head for the new gasket. The little 2" round ones you fit to an electric drill work great. Use caution on aluminum as you can remove metal with them. The Eastwood Company is one source for them. Wipe metal surfaces down with alcohol prior to the gasket installation.
If the head goes to a machine shop: You'll need a head gasket set. Either have the machine shop order you one (preferable Felpro Permatorque), or drop off a set of valve stem seals. If you want to save a few bucks, then remove the rockers (keep them in order: 1 though 8, with the valve lash pads, too. Zip lock bags are great for this) and the camshaft. If you are not sure what to look for, then let the machine shop inspect everything. Cheap insurance.
HEAD GASKETS:
If the new head gasket is dry, and clean, I like using a THIN coat of KOPPER KOAT on both sides. If the head gasket is wrapped in plastic, and has a tacky material on it, then I install it as is on the clean block and head. (OEM NISSAN)
To really confuse me, Nissan also has sold a newer head gasket that is graphite coated with sealing rings around the water and oil passage. It should be installed dry. [Note: I observed this on a U20 Head gasket, but have not recently purchased any L series head gaskets from Nissan] Felpro "Permatorque" is highly recommend by engine builders. Follow their directions.
Always use NEW HEAD BOLTS. Yes, the "turbo" ones. Cheap insurance.
I like to use a thread chaser into the block holes to clean all the junk out of there. You would be amazed how much junk is down there. I make my own by cutting lengthwise groves into an old head bolt. Run it into and out of the hole several times to clean it. Thread chasers are NOT the same as taps.
For the factory installation, the bolts are to be installed with lightly oiled threads, drop of oil under the bolt head. In 1968-72 time frame the factory recommendation was for the bolts to be installed DRY. In the mid-70's this AND THE HEAD BOLT MATERIAL changed to "lightly oiled threads".
Yes, if you use engine oil it will carbonize, hence you need to clean he head bolts (wire wheel on the threads) and run a tread chaser down into the hole.
