SAN FRANCISCO — In the peach-fuzz world of Silicon Valley startups, facial hair is not a common feature.

But engineers at Powerset Inc., a San Francisco company trying to build a better search engine, are bucking convention by growing mustaches. As an expression of solidarity, they vowed to not shave until they finish the company's first product.

They put away their razors in late January as their company hit another milestone in its drive to release its long-anticipated product to the public. About two dozen of the startup's roughly 60 staffers started growing facial hair with the unbridled enthusiasm — if not effortlessness — of Chia Pets.

They're chronicling their efforts at www.Powerstache.com. Powerset's female employees have gone Groucho, too, mugging for the camera with dark whiskers drawn on lips and fingers.

"We wanted something to bring everyone together," software engineer Toby Sterrett said.

The team-building exercise bristles with the kind of individuality that distinguishes Silicon Valley's unusual business culture.

It also mirrors a current fashion statement for American men. Late-night television hosts David Letterman and Conan O'Brien sprouted beards during the Writers Guild of America strike, and some Hollywood stars, sports figures and rock 'n' rollers now show off varying degrees of stubble.

Although Silicon Valley is a youthful place, facial hair has played a prominent role in the high-tech hub. Oracle Corp. Chief Executive Larry Ellison is well-known for his neatly manicured beard. No one pulls off the 5 o'clock shadow better than Apple Inc. CEO Steve Jobs. And few claim fuller whiskers than fellow Apple co-founder Steve Wozniak. He says it suits the freethinking pragmatism of techies, who generally prize simplicity in design and in life.

"Not having to shave is kind of nice," Wozniak said.

During the 1970s and early 1980s, the mustache was almost as popular with Silicon Valley engineers as the pocket protector.

It's also part of Apple corporate legend.

In his book, "Revolution in the Valley," former Apple executive Andy Hertzfeld recounted the story of employee No. 282, Burrell Smith. Smith was designing crucial parts of the original Macintosh computer, but he was stymied as a lowly service technician. He couldn't figure out how to get promoted to engineer — until he noticed that all of them had mustaches. Tom Whitney, vice president of engineering, had the biggest of all.

So Smith grew his own over the next month. On the afternoon he pronounced the mustache complete, Hertzfeld recounted, Whitney called Smith into his office and named him a full-fledged engineer.

"Old-time Silicon Valley engineers did tend to favor facial hair," Hertzfeld said.

Young engineers are paying quirky homage to the past.

At San Francisco startup Lefora, early employee Dan Bragiel is growing a beard and engineer Andrew Seaman is growing a mustache until they roll out a product that lets people create online forums. Turns out it's a great promotional technique.

"You have an excuse to tell people why you are doing it," Bragiel said.

Powerset engineers' fuzz is getting buzz, too, ranging from bemusement to ridicule to prickliness, the latter mostly on the part of prospective dates and significant others. Employees insist their new facial hair has generated camaraderie and comedic fodder (one engineer jokes about a study of the relationship between productivity and unique mustaches conducted by "Selleck, Reynolds, Brimley, et al" ) in a way that other possibilities they entertained — including cornrows, hair dyes, mullets — couldn't have.

Powerset co-founder and Chief Technology Officer Barney Pell is growing a beard as the team sprints for the finish line. As a graduate student at Cambridge University, he vowed not to shave or cut his hair until he finished his Ph.D. thesis.

He thought it would take three months. He finished a year later.

"When you decide you are going to grow some facial hair up until launch, you want to make sure you are really going to launch," he said.

What began as an inside joke at Powerset is now considered "a sign of dedication," software engineer Abhay Kumar said.

About half of the initial two dozen abandoned the pursuit. Some of the engineers who have maintained facial hair complain of itching and find themselves fantasizing about hot towels, white foam and sharp razor blades.

"As part of the Powerset launch, all the engineers are growing out stupid mustaches and keeping them until we have a public product," software engineer David Fayram wrote in the Powerstache blog's first post in January. "I think I've made a terrible mistake."

But those who have held out say it has been worth it to bond with one another and, unexpectedly, with mustachioed strangers who nod when passing on the street.

"It's like you are part of this bizarre club," Kumar said.

The company won't say when it plans to release the search engine. Powersetters haven't yet decided if they will all lather up to shave their mustaches en masse when that happens. Product manager Mark Johnson is counting the days. He says the "untidy bush growing on my chin and upper lip area" has distressed his mother and stunted his social life.

"Frankly, I can't wait until we launch our product," he said.