* Brazil to finance up to $4.3 bln in Venezuelan projects

* Loan helps leftist Chavez fill budget gap

* Financing to help Brazilian contractors (Recasts, adds details, quotes, background throughout)

By Raymond Colitt

SALVADOR, Brazil, May 26 (Reuters) - Brazil plans to finance over $4 billion worth of investment projects in Venezuela as leftist President Hugo Chavez struggles to cope with low oil prices that have created a cash crunch for his OPEC nation.

Until a few years ago, Chavez was using petro-dollars to compete with his Brazilian counterpart, President Luiz Inacio Lula da Silva, for influence among left-wing South American leaders such as Ecuador's Rafael Correa and Bolivia's Evo Morales.

On Tuesday, Chavez welcomed Brazil's aid offer.

"Brazilian companies should be certain that in Venezuela they will have all of our support," said Chavez, who met Lula in the northeastern Brazilian city of Salvador.

"We are so happy, Lula, we are so grateful," Chavez said after a signing ceremony.