Jeff: When you get serious about engines sounds, I have some old records that might be useful: Sounds of Sebring, 1958 ('58 Ferrari Testa Rossa), Bonneville 1960 (Mickey Thompson's 4-Pontiac Streamliner, 32 cylinders) and others. I'll even let you record my Cobra going through the gears (600 HP up to 6200 RPM), but you'll have to make me a copy for my collection).
Rich