Racing's giant firecracker failed to explode in the holiday feature here yesterday, Forego finishing a sad fifth of six in Belmont Park's Suburban Handicap and earning not one dime in his eight-year bid to overtake Kelso as the world's leading money-winning race horse.

Upper Nile won the 1 1/4-mile contest by a length-and-a-half in 2:01 4/5 over the front-running Nearly On Time. Great Contractor ran third, more than two length behind the runner-up and three lengths ahead of Family Doctor.

Then came the "epic" struggle the Belmont crowd of 33,697 had anticipated. Forego, favored at 4 to 4, got up in the last stride to head Cox's Ridge, the Metropolitan mile hero. There two heavyweights carried 132 and 130 pounds, respectively. Everything else was in light, Upper Nile scoring under 114. The last horse to beat Forego with less than a 20-pound advantage was Foolish Pleasure, which prevailed by a nose while getting nine pounds in the 1976 Suburan.

The track was sloppy. Forego's form in such going is checkered. There had been doubt, as late at yesterday's sixth race, whether Forego would compete or be scratched. Trainer Frank Whiteley conferred with jockey Bill Shoemaker. The Shoe said he thought Forego could handle it. Forego couldn't, and for only the third time in his career failed to take home part of the purse.

So the $63.840 first money that would have enabled Forego ($1,938,957) to pass Kelso ($1,977,896) went to Rokeby Stable's Upper Nile. That Nijinsky II colt ridden by Jorge Velasquez now has won four races in a row, including two stakes. He paid $7.20 to win.

Velasquez was able to save ground along the rail throughout the Suburban. Upper Nile was rated in third place, behind Nearly On Time and Family Doctor, until the stretch turn. When Nearly On Time came off the rail, at the top of the stretch, Upper Nile easily moved through and into the lead. He was a half-length ahead a furlong out.

When Forego entered the paddock, he was greeted by a sign held by a fan that read: "Good bye Kelso. You been kool! But from now on the king will reign."

But Forego will have to wait for another day to become king.

"He just did not run his race today," said Shoemaker. "On the middle of the far turn, he did not make his move like he usually does and I knew then that he was not going to do it today."

Speculation will continue as to whether Forego should have run.

"His (left front) ankle looks awful," Whitley admitted. "He popped it last fall and it hurt him at first. It got more calcified, built hasn't continued to get worse. It doesn't seem to bother him."

But a ringbone condition has compounded the problem in Forego's left front pastern. The bony growth has pushed out the front of the pastern into a convex curve. No one can be sure when Forego will race again. Whiteley says the Brooklyn Handicap here July 22 is out of the question.

Not all the great horses made their way to the top of the money-winning list. Secretariat, for example, was retired after his 3-year-old season in 1973 with $1,316,808. He currently holds seventh place on the dollar roster.

Before Kelso took over, in 1964, at the age of 7, Round Table held the No. 1 spot with $1,749,869. Round Table passed Nashua in 1958. Nashua retired in 1956 with $1,100,365, having gained the top over Citation, which retired in 1950 with $1,085,760.

Other money leaders over the years: Stimie, 1947, $918,485; Armed. 1947, $817,475; Assault, 1947, $675,470; Whirlaway, 1942, $561,161; Seabiscuit, 1940, $437,730; Sun Beau, 1931, $376,744; Gallant Fox, 1930, $328,165; Zev, 1923, $313,639, and Man o'War, 1920, $249,465.