DETROIT ? Americans are renewing their love affair with heightened horsepower.

At auto dealers across the country, a growing number of buyers are trading up to sport utility vehicles and trucks powered by big engines such as V-8s and Hemis, machines once shunned as gas-guzzling polluters but now increasingly embraced for their might.

Carlton Jack of The Woodlands, Texas, was so enamored of his Dodge Ram pickup powered by a Hemi that he bought another for his wife, Lourdes, at Christmas.

“Fuel consumption wasn’t a consideration,” said Jack, a Houston police officer and former Ford truck owner. “I wanted the power and performance of the Hemi, and I liked the looks of the Ram. That’s what sold me.”

Automakers installed large V-8 engines in 29.1 percent of all passenger vehicles built in North America for the U.S. market last year, the highest rate since 1985, according to Ward’s Automotive Reports. The rate has continued rising every year since 2000, when V-8s went into 25.3 percent of North American-built cars and trucks for American drivers, according to Ward’s statistics.

In the same four-year stretch, smaller 4-cylinder installations fell from nearly 27 percent to 25.3 percent.

Analysts and industry executives give a variety of reasons for the rise in V-8s, which use more fuel but produce more power than smaller engines: strong demand for trucks and sport utility vehicles, relatively inexpensive gas prices, and technology that’s leading to improved fuel efficiency, even in bigger engines.

Environmental advocates say making vehicles more powerful is the wrong approach; Detroit automakers should be focusing instead on hybrid and other “green” technology that foreign makers excel at.

“There will always be a market for the gas-guzzling powerhouse, but the American manufacturer seems to be willing to lose market share as Toyota and Honda bring in better technology,” said Daniel Becker, director of the global warming and energy project for the Sierra Club. “It’s unfortunate that Detroit confuses horsepower with quality, and it’s why more and more Americans are buying imported vehicles.”

Carlton Jack, right, and his wife, Lourdes, look at the engine of one of their Hemi-equipped Dodge RAM 1500 pickups at their home in The Woodlands, Texas. Carlton Jack loved the engine truck that he bought for himself last year, so he bought one for his wife at Christmas.