There are those who will tell you that little Johnny Sylvester was never that sick and certainly not dying.

They will tell you that Babe Ruth never promised to hit a home run for him in Game 4 of the 1926 World Series, and that the three home runs the Babe did hit in that game in no way saved the 11-year-old youngster's life.

Any representations to the contrary, these people will tell you, were simply embellishments of a trivial incident by an oversentimental press in a hypersentimental age. Home Runs a Cure? But as the record makes clear enough, Johnny Sylvester was severely ill in October 1926. And Babe Ruth did promise him a home run. And if the three homers Ruth hit against the Cardinals in St. Louis on Oct. 6 did not bring about an instant cure, they most certainly did no harm.

For little Johnny Sylvester not only lived to tell the tale, he also spent the next six decades doing just that.

And when John Dale Sylvester died on Monday at the age of 74, it seemed occasion enough to tell it once more.

Mr. Sylvester, who lived in Garden City, L.I. and died at Winthrop University Hospital in Mineola, was a 1937 graduate of Princeton University who served as a lieutenant in the Navy in World War II and later as president of Amscomatic Inc., a manufacturer of packing machinery in Long Island City, Queens.

There was nothing Mr. Sylvester could have done to match the pinnacle he reached in 1926 when he became the most famous little boy in America.

Speculation Over the Illness

One reason the skeptics have had a field day debunking the incident is that a range of ailments were ascribed to Mr. Sylvester, among them blood poisoning, a sinus condition, a spinal fusion, a spinal infection, and a back problem.

According to his son, John D. Sylvester Jr., and at least one contemporary account, the ailment was an infection of the forehead caused by a kick from a horse after the youngster fell while riding, in Essex Fells, N.J. His father, Horace C. Sylvester Jr., a vice president of the National City Bank in New York, maintained an estate there.

Most accounts indicate the youngster was dying. One had his doctors giving him 30 minutes to live before he rallied after his father vowed to fulfill his last request for a baseball autographed by Ruth.

It is still unclear whether the youngster initiated the request for an autographed ball, or whether his father or an uncle decided such a present might cheer him up.

What seems clear enough, however, is that urgent telegrams went out from the family to the Yankees in St. Louis and back came an airmail package containing two balls, one autographed by the Cardinal team and the other with the signatures of several Yankees and a special message from Ruth: ''I'll knock a homer for you on Wednesday.''

A Hollywood Version (The version of the incident in the movie ''The Babe Ruth Story,'' showing Ruth delivering the promise at the youngster's hospital bed, seems to have been wrong on at least two counts. The promise was not made in person and the youngster was apparently never in a hospital.) The Babe did better than that, of course, but even he was not invincible. A follow-up note from Ruth ''to my sick little pal'' dated Oct. 9, the day of Game 6, said ''I will try to knock you another homer, maybe two today.''

Alas, Ruth went without a homer and the Yankees lost, as they did the next day when an unpromised Ruth home run was not enough to save the game or the Series for the Yankees.

Or as a consoling Johnny Sylvester told the Babe when Ruth made a well-publicized visit to the youngster after the Series, ''I'm sorry the Yanks lost.''

In addition to his son, John Jr., of Huntington Station, L.I., Mr. Sylvester is survived by a sister, Ruth Elliot, of Barrington, R.I.; a brother, Horace C. Sylvester Jr., of Osterville, Mass., and two granddaughters.

John D Sylvester