Originally Posted by lunchboxx
Yeah I noticed that. The plenum bolts are 8mm. The lower intake manifold was 3/8 standard. I was walking back and forth to the toolbox scratching my head to figure out what was going on. Usually, I just take 10,13, and 15 to the hood and thats just about all I need.
With these motors, you are going to need a set of metric and SAE taps (perhaps even a couple of NPT taps too.) For instance, the oil pan bolts are 1/4"-20, yet as you discovered, the top of the motor is mostly metric
The route GM took towards "metric-izing" the existing motors was to leave the blocks alone and do the accessory drives, fuel system, and other optional parts first. (Where they become part of a common "pool" of metric parts used on multiple engines.) It'* not much of a savings in tooling costs, but it does add up in reduced parts inventory.
You can thank all that "global economy" bs. There'* nothing wrong with the SAE system IMHO.