This is a long shot, but you might be thinking of the bolded passage below:
Arcot and Wade were laughing, but not Robert Morey. With a sorrowful expression, he walked to the window and looked out at the hundreds of slim, graceful aircars that floated above the city.
"My friends," said Morey, almost tearfully, "I give you the great Dr. Arcot. These countless machines we see have come from one idea of his. Just an idea, mind you! And who worked it into mathematical form and made it calculable, and therefore useful? I did!
"And who worked out the math for the interplanetary ships? I did! Without me they would never have been built!" He turned dramatically, as though he were playing King Lear. "And what do I get for it?" He pointed an accusing finger at Arcot. "What do I get? He is called 'Earth's most brilliant physicist', and I, who did all the hard work, am referred to as 'his mathematical assistant'." He shook his head solemnly. "It's a hard world."
At the table, Wade frowned, then looked at the ceiling. "If you'd make your quotations more accurate, they'd be more trustworthy. The news said that Arcot was the 'System's most brilliant physicist', and that you were the 'brilliant mathematical assistant who showed great genius in developing the mathematics of Dr. Arcot's new theory'." Having delivered his speech, Wade began stoking his pipe.
Fuller tapped his fingers on the table. "Come on, you clowns, knock it off and tell me why you called a hard-working man away from his drafting table to come up to this play room of yours. What have you got up your sleeve this time?"
"Oh, that's too bad," said Arcot, leaning back comfortably in his chair. "We're sorry you're so busy. We were thinking of going out to see what Antares, Betelguese, or Polaris looked like at close range. And, if we don't get too bored, we might run over to the giant model nebula in Andromeda, or one of the others. Tough about your being busy; you might have helped us by designing the ship and earned your board and passage. Tough." Arcot looked at Fuller sadly.
Fuller's eyes narrowed. He knew Arcot was kidding, but he also knew how far Arcot would go when he was kidding—and this sounded like he meant it. Fuller said: "Look, teacher, a man named Einstein said that the velocity of light was tops over two hundred years ago, and nobody's come up with any counter evidence yet. Has the Lord instituted a new speed law?"
"Oh, no," said Wade, waving his pipe in a grand gesture of importance. "Arcot just decided he didn't like that law and made a new one himself."
"Now wait a minute!" said Fuller. "The velocity of light is a property of space!"
Arcot's bantering smile was gone. "Now you've got it, Fuller. The velocity of light, just as Einstein said, is a property of space. What happens if we change space?"
That's from the Project Gutenberg etext of the Ace Books edition of John W. Campbell's novel Islands of Space in his Arcot, Morey and Wade series. I suppose Morey could be your "O'Malley" although Arcot was the main inventor of the FTL drive and Morey merely his "mathematical assistant". But they are not exactly saying "Einstein was wrong" so this is not a very good match to the question. Like I said, a long shot. (My first guess was The Skylark of Space but that's already taken.)