In this case, think in terms of the process a draw-er would use to draw that concept.
They would start with an oval, like an egg.
"It was like an egg."
In this case, it is longer than an actual egg.
"If that egg had been smushed on the top so that it spread sleekly and smoothly at each end."
They would add lines and curves to define the wheel wells and windows.
"Of course, most eggs don't come with windows. And these were beauts. Odd angles, sloping, begging for speed."
Then add a little flair at the end.
"And most eggs aren't polished, either, to such an extent that seemed to come from another world."
First draft (I usually need four before I'm happy with something.Take it or leave it.):
It was like a silver egg, if that egg had been smushed on the top so
that it spread sleekly from each end. Of course, most eggs
don't come with windows. And these were beauts. Odd angles, sloping,
begging for speed. And most eggs aren't polished either, to such an
extent that it seemed to come from another world.
I think the key thing in this suggestion is to start with a known object that is not a car, so that the reader approaches it ignorant of 'car.'