The Timken Museum, the bastion of old masters, is going pop.

The free museum in Balboa Park is displaying nine contemporary art pieces from some of the biggest pop artists of the 20th century. Andy Warhol and Roy Lichtenstein are just two of the artists whose works will be integrated into the museum’s collection for the exhibition “Metonymies: A Dialogue of Twentieth-Century Works from the Sonnabend Collection.”

The idea is to shake things up a bit and spark some conversations. One contemporary piece is substituting one work by an old master in each of the museum’s five permanent galleries. The remaining contemporary pieces will each be displayed next to a piece from the permanent collection in the temporary Exhibitions Gallery along with the artwork that was swapped out in the other galleries.

“We wanted to make sure any contemporary pieces we bring in always have a connection to the collection,” said Megan Pogue, the museum’s executive director. “It has to make sense for the Timken.”

“Ileana was one of the 20th century’s greatest gallerists. She had an incredible way of discovering young artists. She was so far ahead of her peers,” said Derrick Cartwright, director of curatorial affairs at the Timken. “The pop artists that Sonnabend championed are now mainstay.”

Sonnabend helped steer the course of 20th century art with her galleries in Paris and New York. The Paris gallery, opened in 1962, introduced Europe to American pop art. In 1970, she launched a gallery on Madison Avenue that later moved to SoHo, where it was instrumental in establishing the neighborhood as an international arts center. Sonnabend, a native of Romania, died in 2007 days before her 93rd birthday.

Her foundation holds many pieces of her vast private collection. The loan to the Timken was through Liz Anne and Phokion Potamianos of La Jolla. Potamianos’ father, Antonio Homem, the chairman of the Sonnabend Collection Foundation, is the adopted son of Sonnabend.

Cartwright came up with the name for the exhibition because like metonymies, there are similarities between the old masters and the contemporary pieces that are temporarily taking their place. Sometimes it’s the content, other times it’s the subject matter.

“The substitutions and comparisons will change opinions of the work we have,” Cartwright said. “We think that when people step in (a gallery) they will notice something different. It’s a little bit of a ‘Where’s Waldo?’ kind of puzzle.”

Among the pieces on loan are two by Andy Warhol. His portrait of Sonnabend has been exchanged for Bartolomeo Veneto’s “Lady in a Green Dress.” Veneto’s unknown woman is seen looking to the right with a slightly pensive expression. Warhol’s Sonnabend is also looking to the right with a thoughtful look.

Warhol’s “Jackie (Gold),” a silkscreen on canvas from a photo of Jackie Kennedy at John Kennedy’s funeral, will substitute for Anthony van Dyck’s “Mary Villiers, Lady Herbert of Shurland.” Villiers is also in mourning, wearing a gold dress and holding a wilting flower.

“These are important political women in a moment of mourning,” Cartwright said. “They have some things in common and some things quite different.”

Warhol’s Kennedy, which has been on loan at a museum in Italy, will be on display beginning March 19. Once the Van Dyck is returned to its original spot, Cartwright said, “We’ll never look at the painting quite the same way.”

Perhaps the most jarring substitution is Tom Wesselmann’s 3D still life of a turkey for Raphaelle Peale’s realistic still life of a cutlet and vegetables. Wesselmann’s fiberglass turkey is reduced to essential forms in a statement on American consumerism.

“Realism is so important to Peale. Wesselmann likes that idea and makes it revolting at the same time,” Cartwright said.

The substitution of a Lichtenstein piece (one of two in the exhibition) in the Russian Icons Gallery is a bit more surprising. But, Cartwright said, the famous pop artist’s 3D piece titled “Small Explosion” relies on the same strategies the Russian icon painters used to create supernaturalism.

Jeff Koons is represented by a cartoonlike sculpture of Bob Hope, which stands side-by-side with a bust of Walter Ames by Ruth Hayward. Ames was crucial in the establishment of the Timken Museum and the two pieces are a look at how men are monumentalized with sculpture.

Other artists in the show are Lawrence Beck, Hiroshi Sugimoto and Candida Höfer.

“This is the biggest blend of contemporary and old masters that we’ve done,” Pogue said. It’s a chance for the Timken to attract visitors who wouldn’t normally be drawn to the traditional collection. “Five-hundred-year-old paintings may not have that sizzle for younger audiences. We’re hoping we can attract a younger crowd and build that bridge to our collection.”

The exhibition is intended to be fun, Cartwright said, who spent months picking out the pieces to replace and pair. The Sonnabend collection has more than 1,000 works of art.

“People are definitely going to be talking about it,” Pogue said.