Our Sheriff's Dept. did the same tests here with the same results. Even the 9mm blew right thru the car, not engine but thru the car. They did the test to see if a car is a good thing to hide behind during a shoot out, lets just say, I would find something else to hide behind.
A car might have 1/16" of steel and another 1/2" of plastic and insulation to go through, I'd be
suprised if a .223 or 9mm
didn't go all the way through- it would be like shooting at a long row of beer cans. An engine block is a completely differetn story. As far as using a car for cover, I'd feel relatively safe with an engine block between me and a shooter, and almost as safe behind a wheel where you have a few inches of steel/aluminum from the brake drums/rotors + wheels.