It's "Silicon Valley" meets "Shark Tank" and "Cash Cab."

On Wednesday, folks with plans for The Next Big Thing have a shot at a one-on-one short pitch to venture capitalists from Google Ventures, Google's powerhouse VC investment arm that pumps as much as $300 million a year into startups.

In a promotion with ride service Uber, six partners from Google Ventures will each ride in the backseat of Uber cars cruising through Silicon Valley from 11 a.m. to 3 p.m.

Hackers, visionaries and future moguls in Palo Alto, Mountain View or Menlo Park can request an "UberPitch" ride through the company's smartphone app. Those selected will have seven minutes to make their case and seven minutes to hear feedback.

"This sounds like a ton of fun," said David Krane, general partner at Google Ventures, who will be along for the ride. "It's a creative opportunity for some serendipitous meetings with people who have a lot of passion and enthusiasm behind their ideas; people we otherwise wouldn't have had an opportunity to meet."

It's no coincidence that Google Ventures is on board with Uber's promo stunt. Krane is an observer on the Uber board and led Google Ventures' $258 million investment in Uber last summer. It was the VC firm's biggest-ever outlay.

While Google Ventures' primary motivation is to support Uber, Krane said he thinks there's a better than 50 percent chance that the stunt could yield a business relationship.

"This is where the highest concentration of the most-talented entrepreneurs live," he said. "If we meet someone with an idea so captivating that we might consider making an investment, that would be a tremendous plus."

Google Ventures has a large appetite for small investments in seed-stage companies. It typically writes 40 to 60 "small checks" a year of $100,000 to $250,000, he said.

The VC firm did cattle-call-type pitches once before in a speed-dating-type event at the Google I/O conference at Moscone Center in 2011.

"There were long lines of bright-eyed, bushy-tailed entrepreneurs from all over the world," Krane said. He and his partners spent two minutes each with some 600 or 700 people. He's still in touch with people he met, but that event didn't yield an investment, as Google Ventures focuses on U.S. companies and most of the folks pitching were from overseas.

UberPitch has a better structure, he said. "It's a higher-quality environment for more-productive conversations in the quiet and serenity of the back of a car."

Past Uber promotions have sometimes been overwhelmed by demand. On National Cat Day in October, the San Francisco company teamed with I Can Has Cheezburger? (the folks behind LOLcats) to offer kittens on demand for 20 minutes of playtime at offices in San Francisco, Seattle and New York - and they ran short of furry friends.

How will Uber manage the load this time?

"There are thousands of strong ideas, but just six investors for UberPitch, so demand will be high," it said in a blog post. "If you don't secure a pitch on your first attempt, keep trying! Nothing ventured, nothing gained."

While the chance to score an investment from one of Silicon Valley's leading VC firms may be priceless, the rides will be free.

©2014 the San Francisco Chronicle