robertf said:
Aluminum blocks were more difficult to make, and had a lower yield (more factory defects per 100 blocks made). Weight was not an issue back in the 60s, so going with aluminum block would be making the car more expensive for no apparent reason. A gallon of regular gas was 30 cents back in the 1960
Things changed in the 1970s and 80s. GM started putting aluminum heads on iron blocks and eventually built an all-aluminum engine when weight became enough of an issue. By that time the old small block was a rather outdated design that did not allow for high enough compression to meet emissions standards. LT1 engines had their cooling system redesigned which allowed for higher compression, but they had their own set of issues. So instead of making an aluminum version of LT1 or LT4 folks at GM designed a new engine - LS1. They also flirted with DOHC setup but quickly discovered the same thing that Porsche learned the hard way on their 928 motor - DOHC V8 with 4 valves per cylinder are heavy as all hell and not particularly reliable.
