Timely response as I am in the midst of doing an elbow. I finally, after four tries,found a head that was not cracked and put it on yesterday. I also searched the net on the elbow methods and torques. Opinions vary and the torque specs have been changed several times over the years (generally going down a little). The whole thing, IMO, is a crappy design that lends itself to problems.
I noted how in my earlier installation, using the black gaskets, it seemed to seal very well between the gasket and the cast iron, but not between the gasket and the stainless block off plate. This time I carefully put a very thin layer of high temp RTV on the gasket to plate surface (coating the gasket not the plate so as to leave the steel surface open to the coolant and salt - based on erich's theory of the need to cool the block off plate). I then torqued the whole thing to about 15 pounds. I like to hold the shaft of the torque wrench at the same distance as the length of a 9/16" open end. That way when I do the two nuts that you must use an open end on I have a feel for how hard to pull the wrench. I have allowed the layer of RTV to cure over night at the lower torque and I will soon go down and finish torquing to 28 ft. lbs. After a heat up and cool down (assuming it starts!) I will re-torque. Hopefully this time it will remain tight.
Thinking about what seems to me to be fairly low torques with soft gaskets for such a critical joint I wondered why it isn't a hard gasket with high torque, like the head gasket I just installed. I think possibly the problem is the expansion of the elbow in normal operation (and even more so if the elbow runs hot with poor water flow). This will put additional stress on the long bolts, that run much cooler, and could snap them or cause a permanent yield (stretch). So the bolts may have a much higher torque when the elbow is hot than when cold. Combined with the soft gasket this creates the need to re-torque after installation and use.
Also I did find that I needed to run a tap in the two long bolt holes to clear out the rust that would have messed up my torque readings.
I should be fishing tomorrow.