S/C is FAR more easily upgradeable. All you have to do is by an overdrive pulley , they have different percent overdrives. the higher percentage yeilds more horsepower the higher percentage the more upgrades you haved to do to support the engines needs, with your lofty 250hp goals you will need fuel management, larger injectors ,headers,exhaust Ect ....
With all these mods of course there will be a MPG impact there is no such thing as free HP you'll likely be down to 20mpg
Also with the upgrades come reliability issues, you are making the engine work harder of course things can/will happen
|