He said, in the section you quoted, that it is *louder* in reverse, not only audible in reverse.
I'm glad Hurricanes started this thread but I don't understand 1) why an iron block is believed to last longer than aluminum and 2) why guys with only 100k are talking like that's a lot of miles. Where are the 200-300k people at?
As cast iron is heat cycled, its hardness increases throughout its structure. Of course, while this means the engine block is more brittle and stiff (and therefore stronger, since resistance to deflection and deformation is considered strength in engine terms) it makes it more prone to cracking around casting flaws or intrusions (usually around coolant, oil passages, or bolt/stud locations and such). You may have heard the term "aged" used with engine blocks... this is what they're referring to. Essentially, an aged block is going to handle extreme stresses with less deflection better than a young block still warm from the foundry. Old school guys used to surf scrap yards for their next performance block, instead of rolling into the dealership, hoping for a motor with favourable core-shift in an old van hulk.
The 2UZ, the 4.7L V8, is bi-metal: cast iron block and aluminum heads. This means that it's likely a metal headgasket from the factory with a very smooth finish on the mating surfaces. Since Al and CI expand and contract at different rates, they'll slide around on each other but stay sealed. The 7M had plenty of problems with its composite headgasket. Toyota dropped the M in favour of the JZ with its stock metal headgasket. The 5VZ also has a metal gasket from Toyota.
Al heads/CI blocks bi metal engines have been around for...ever. The R, VZ, JZ, M, G engines... ones that I can name off the top of my head, were all bi-metal, and generally regarded as bomb proof in all their iterations.
Aluminum can achieve what's called a "soft" condition, or annealed state through heat treating (this threshold is much higher than an engine should ever get, though). Great for working aluminum in industry, horrible for aluminum motors. Heat cycling alone can make aluminum weak around high strain/high heat areas like exhaust studs after a few decades. This is why all aluminum engines are so vulnerable to overheating... A high temperature overheat will accelerate this process. In a bi-metal engine, the cast iron block can take an insane amount of energy to get real hot... prolonging the life of the aluminum heads. Ever cooked with an aluminum pan and a cast iron pan at the same time? You'll see the difference in action. I've thrown out plenty of aluminum pans... but I have my great grandmother's cast iron pan handy for doing breakfast up.
Anyway, an all aluminum motor shouldn't be overheated at all costs.
Nonetheless, the 1GR is a great motor. In my opinion, it has to be to live as long as they are living, make the specific power they do, and live life in a truck. I do believe the 5.7L Tundy motor is all aluminum as well. It towed the space shuttle so I'm sure it's fine too.
For those that didn't bother to read the bulk, highlights are that cast iron motors are alot more forgiving for design mistakes. All-aluminum motors must be designed perfectly and kept in good form to last a long time.
