SAN FRANCISCO -- Elon Musk gave a public shout-out to the sharpest minds in manufacturing this week, calling on them to come help Tesla Motors Inc. build a million all-electric cars a year by 2020.

Musk says he is "hell-bent" on making the Silicon Valley automotive upstart a manufacturing powerhouse, but his vision relies on finding veteran auto engineers to ramp up volume ten-fold in four years -- a challenge even for established carmakers.

Tesla on Wednesday said it would build 500,000 cars in 2018, two years ahead of schedule, and close to 1 million by 2020. The same day Tesla said its vice presidents in charge of production and manufacturing were leaving.

"You're looking at a company with significant levels of management turnover at the highest ends, people without experience in the planning, design or build of vehicles, and you expect to crank it up at those kinds of volumes?" asked Michigan-based auto manufacturing consultant Michael Tracy.

Shortage of engineers

Putting aside the issue of capital requirements, auto experts point to a shortage of manufacturing engineers, whose ranks were thinning out even before the U.S. auto crisis hit in 2008.

"It's a constant issue we have in this country," said Garth Motschenbacher, director of employer relations at Michigan State University's College of Engineering.

"For the longest time manufacturing was seen as the dirty end of engineering," he said.

At the same time, Google and Apple are working on car programs and courting the same potential employees. So are established auto names like Ford Motor Co., General Motors and Toyota Motor Corp.

A 2015 Deloitte report found it takes three months to hire skilled engineers, and the shortage is crimping manufacturers.