Lets talk about the best racing engine ever. the opel calibra touring car 14,000! RPM opel won with a very well designed engine v6 capable of smashing bigger motors v8 v10 ect. and the sound was beautiful.

The Opel Calibra touring car engine was good, and in a great car. I don't think it's the best ever, though. Assuming that we're talking road racing, my top 3 engines are:

1. early 1990's BMW F1 engine. 1200+ HP from a 1.5L turbo 4
2. Porsche 917/30 5.0L twin turbo flat 12 with an estimated 1500+ HP at full boost
3. 1993 Toyota GTP engine. 1200+ HP from a 2.2L turbo 4 that lasted long enough to win the 24 hrs of Daytona.

These are based on power, reliability, and new technical innovations for their era. Though the Calibra was a good engine, there was nothing particularly revolutionary about the Calibra engine, as there were both more powerful and higher revving engines around prior to it.

Heck, the Opel V6 isn't even close to the best V6 in racing.

World's best V6? The glorious Dino V6 that Ferrari and Lancia used (and won with) in F1, sports car, rallying, and hill climbs as well as in production cars from 1955 (when Vittorio Jano and Alfredino Ferrari persuaded Il Commendatore to try the new engine layout) to 1979 (when the Lancia Stratos won its last Monte Carlo).

Just a sampling of winning Dino V6 powered cars.

http://www.autosrapidos.com/superautos/f/ferrari-dino246gt01.jpg
The 246GT Dino road car

http://www.maranello.cc/All.Ferraris/images/0285/121-2160-img-1.jpg
the 156F1 "Sharknose" (Phil Hill won the first World Driver's Championship for an American in one of these cars)

http://www.atlasf1.com/2001/san/preview/okeefe11.jpg
the 246F1 that Mike Hawthorn won the 1958 World Driver's Championship with.

http://www.racingsportscars.com/photo/1961/Sebring-1961-03-25-026.jpg
the 246S sports car (most famous for incredible runs in the Tour de France rally/hillclimb and the Targa Florio)

http://www.racingsportscars.com/photo/1961/Sebring-1961-03-25-027.jpg
the 246SP prototype which challenged Ferrari's then dominant 250TR Testa Rossas and birthed the mid-engine program at Ferrari.

http://www.motorimania.it/manifestazioni/sportprototipi/images/0.Ferrari.206.Dino.1.jpg
the 206SP that again was a master of the Targa Florio, often showing up the much faster 330P3's on tighter courses

http://www.1motormart.com/gallery/74lanc01.jpg
and the Lancia Stratos that is the single most dominant car to ever compete in rallying and that finished off the lifespan of this incredible engine.

Sorry, a 14,000RPM sewing machine doesn't have a thing over an engine that walked over the world of racing. I believe I am correct in stating that the Dino V6 is the ONLY engine to ever capture the World Championship in Rally, F1, and Sports Cars.

I had forgotten about the Dino V6. Because engine technology is changing so fast now, I don't really consider longetivity to be a major factor. That having been said, when it was first introduced, it was certailny revolutionary, and at the end of its rin in the Lancia, it was turbocharged AND supercharged. Though the plumbing must have been a nightmare, it was definitely something that has never been seen before. I'm still wouldn't put any individual iteration of it in the top 3, though it is close, but it is the top V6 I can think of if you consider its entire lifespan.