I was shocked too that was when I saw the prints and CAD data for the R07 block and heads. Having worked for GM Racing you get to see things like that. But the block alone is like 225-250 or so. Almost mega block wt. That is where the wt is at.

One thing I worked on when I was at GM was wt reduction of the heads. Trying to find a few ounces here and few there. Without compromising the heads. The blocks the teams lightened if they wanted. But that much wt that low, is better then wt higher up. I think I saw mentioned the cars are titanium so add an extra 4 pounds to the numbers you saw.

Yes the heads are almost as big as my Indy heads for my BB. Crazy stuff.

The water cross over is only like 2-3 lbs, not much but it adds up.

If I can be of any more help let me know.