The nuts are brass, 7/16-20 x 5/8, NAPA part number STX104X, 27 lbs of torque. Studs are 1-5/8 long 7/16-14 lbs. NAPA part number for the stud is 86632. Use washers. If you don’t get them at NAPA, make sure that the stud has an egg-shaped center between the different threads.
Clean all the threads in the block w/ a thread chaser. If you are reusing old studs (and I never would) clean them well w/ brake or carb cleaner.
There are two distinctly different recommendations on tightening the studs in the block. Because the stud goes into the water jacket & is constantly undergoing extreme heat & cooling cycles, some folks like to double-nut them & tighten them down at 37 lbs of torque. Others say that it’s a stud & should only be finger tight w/ a good dose of thread sealer or high temp silicone on them.
I’ve replaced the studs on 2 of my 3 N’s w/ no leaks; I finger tighten the studs then take a turn on them w/ vice grips.
Make sure you put the clamp on correctly; check out tip # 8, below.
Do not try & hold the exhaust pipe against the manifold w/ your hand & tighten the clamp. Get out your floor jack & a block of wood; put the jack under the pipe to hold it tightly against the manifold, then tighten the clamp. (Don't get carried away w/ the jack or you will bend the pipe. Or, overtighten the clamp & snap it in two. BTDT)
If the exhaust pipe flange is bent, you will never get a good seal; check it out.
Use gaskets on the manifold. Again, there are two schools of thought on using the Copper Coat sealer & none at all. The reason for the gasket sealer is that the manifold is both an exhaust & intake manifold. The reason not to use sealer is that it will just burn off. I've done it both ways, but I've used sealer on the last two I did.
Valve cover gaskets are easy to get; I much prefer them to any kind of "gasket maker", because I will be the next guy inside of the engine that has to clean that crap off.
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