Depends entirely on the design of the engine. Historically those engines that were never equipped with forged cranks tended to have much thicker crank designs (for example Pontiacs have up to 3.25" bearing journals!) for brute strength, while engines that were supplied with both generally limited cast cranks to low horsepower (eg 2bbl) variants. 250hp would probably be fine though.

Cast cranks theoretically have the advantage of not "ringing" so are less reliant on a harmonic damper to absorb potentially destructive resonant vibration.

12:1 on a street driven car is not recommended. Plugging in [ (1 - 1/ 12(.4)) / (1 - 1/ 10.5(.4)) ] -1 x 100 we find an increase in compression ratio from 10.5:1 to 12:1 should result in a 3.9 percent increase in power, which is not worth a lot once you consider that it requires the use of $8/gallon unleaded race gas everywhere you go (a few lucky places do have 100 octane gas available, but I bet it costs a lot in Canada). Kind of a waste when you consider such gas could easily support 25+psi of boost, which would improve power a whole lot more than 3.9%. Besides, the wastegate could then be limited to ~18psi when using pump gas, making for a more flexible setup.

The only way to reach 12:1 is to use a domed piston, which erases any advantage of quench in controlling detonation.

 

bummer..

 

Ranzo...How much was shipping for that tranny? Expensive coming from the UK?

 

No it wasn't expensive, dealer was going to charge me 2500 for the tranny, the tranny I got costed me about 1600 to 1700 bucks shipped. But I think Mini Mania might have raised they're prices.