I read this book in the 80's, but it was pretty old at the time. What I recall:
- Hero character is a secret agent of some kind.
- Technology organization ("Q Branch" basically) provides him with some sort of atomic vehicle, upon which they put a governor to prevent it from going past the speed of light. Like Chekhov's gun or "never press this button!", in the last part of the book he has to remove it in order to go back in time (or something).
- He has to go to the villain's lair, but he takes some sort of medicine which enables him to reshape his face (like putty) in order to pose as the villain's son.
- The villain manipulates events so that he gets a minor poke, drawing blood, and he secretly has the hero's blood analyzed, and it's the wrong bloodtype. ("My son's blood is type O").
It had a pulpy, Tom Swift type of feel, and it wasn't at all high literature. But I'm wondering what it was. I'm pretty sure that the events listed above were all in the same book, but I may be conflating two different series.