The plastic intake was made to save money and weight, and the design was also to increase performance. GM could have made an aluminum intake with the same design that would have given the same performance.
As for what damages the engine when these intakes fail, it is the hydro-lock that occurs when the coolent is ingested into the engine. Coolent, being two dense to flow through an engine at 2000 RPM, will lock up the engine, causing bent/broken rods and valves, and possibly spinning the bearings in the process. The other scinario--as Will pointed out--is that the engine may seep all the coolent out over time, not producing a hydrolock situation, but causing the engine to overheat, which in turn renders the oil ineffective, thus allowing your engine to score and/or spin the bearings. Neither situation is favorable.
These engines are great engines. The lack of maintanence of one poorly designed part can be a fatal mistake to an otherwise near-perfect engine. GM will not conceed to replacing or redesigning this part as it would open them up to lawsuit. It will not be a recall issue because it has nothing to do with safety. The only way to change this is to link fatalities to this problem--which, given the safety features of the H-bodies, is very unlikely. Hectors breakthrough (if he developes one) would have the potential to put ADTR on the map with the right price and marketing.
Retired Moderator, The Bonneville Club www.bonnevilleclub.com
RIP Oldsmobile, April 29
1995 Bonneville SE Supercharged (Stock)
Current Mods: Dirty GYM Sock air freshener.