Warning: .26 = POS DO not buy!!
There were a few times when I would hit the "sweet spot" with this motor and it has ungodly amount of low to mid range. I never got a lot out of the top end but it wasn't running right either.
One of my friends at the track who also has a C5 stated that the day before I was there that there was a guy who's .26 was running with his C5. However, the guy with th .26 said told my buddy that he had a hell of a time getting his engine to run decent but when it did it had a heck of a lot of bottom and top end.
As for the Hyper 8 port, I know two guys that run them and they are very good dependable engines and can compete with the high end engines. They may not win down the back straight away but they will hang. Good motor but tight as hell to break in but any good high compression engine is going to be tight. You will need to turn it over my hand using a wrench or a drill hooked up to it.
The RB concept C5 or WS7s are excellent engines. If you don't mind spending the money they are great engines and worth the price. To bad they're French though!! lol
The Novarassi Black Magics run really well at the track too.
However, I would go with a C5 or Ws7. I went with the .26 because of the price and I guess I may have gotten what I paid for which is a big piece of dog dung. However, I am going to check my fuel filter to make sure it wasn't leaking or messed up.