More like 10,500 rpm if memory serves. The straight-cut supercharger gears spinning at 25,000 rpm put out a scream that would put a Banshee to shame. I heard it many times on the radio while listening to the 500 with my Dad "way back when". TV coverage then never cut it from the sound standpoint -- on the radio, you could hear that thing coming from Turn 4 all the way down the front straight. Incredible.
I think Andy Granatelli got the final iteration of this motor up to over 700 hp (compared to the 600 hp of the Offenhauser that everyone else ran at the time), and Tom Rathmann was the only driver with the skill (balls) to run it without an 80% throttle block. There's footage somewhere of Rathmann lighting up all 4 tires coming out of turn 4 on lap 1 and completely blowing past the leader who was about 10 lengths ahead of him.
An incredible motor that was deliberately excised from Indy competition by the Rules committee when they changed the max displacement from, I think, 187 c.i. down to 160 c.i.. This was simple for Offy engines because they used sleeves, but the Novi was a solid block and could not be modified. The rules committee continued this trend in later years, protecting their little fiefdom from innovation and competition, when they later banned 4WD, then restricting the intakes of the turbine cars so much they couldn't compete, plus many more "adjustments" in following years.
Here's a link to a little historical account of the Novi if anyone's interested:
https://www.youtube.com/watch?v=FBHBmq7bnHs
