I have used the Threebond 1211 for some many years now, and it works very well. If you are too impatient to let it cure naturally, a small amount of heat will accelerate the curing process. Such as a hot plate on lowest setting, heat gun, or simply letting it rest in the sun on a warm day. 150deg F seems to work well but I wouldn't go much hotter than that.

As for the theory behind the mystery putty itself, the reason for it's placement is two fold. One, it is there to fill the void left by the machining process in crankshaft manufacture, thus straightening the pathway from the carb to the crankcase. And two, it acts as a crankcase stuffer. By occupying area in the crankcase it raises the primary compression slightly. This can be a good thing sometimes and also a bad thing depending on the engine design and intention of modified engine power delivery.

However, I have done a little research with crankshafts on the dyno and I have yet to see any change in power from any engine both with and without the magic putty in place or not. You are much better off altering the crank's intake timing to see differences in power.

This mod is definitely more show than go! Surely a selling point to people investing in trick or modified engines. On the other hand, I really can't see any harm in doing this to an engine as long as you use a material that is engine safe (won't cause damage to the engine if it comes loose and goes through the engine).

BK