Hi this is my first time posting here so let me know if im doing something wrong. I bought a 2005 cobalt ss about 5 months ago. Ive been daily driving it since. its an amazing car after coming from an old v6 mustang. The one i bought has low miles (95k) but alot of work done to it including ported heads and m62, full 3 inch catless exhaust with longtubes, 80# injectors with e85 and a 2.6 pulley. I was told its making 300 whp. Ive decided its simply too much power for my taste and i want to go to a less aggressive setup. My question is how do i go about switching to a larger pulley (probably 2.9 to 3.1) and switching to 91 octane with 42# or 60# injectors Do i need to go to a dyno or can i somehow switch it myself. My goal would be to have a reliable daily driver with 240 ish whp without spending much money.

 

Pay for the best dyno guy in your town and you won’t regret it. I love my 2.9 and 42’s. You can beat the throttle like an On-Off switch and never worry. Anything smaller has diminishing returns and more heat. With your ported head that is freeing things up you could get away and achieve what you want with a 2.8 and 60’s and thats the combo those that play harder run. Do the 2.9 and 42’s and beat it as hard as you want, get better milage and piece of mind that you are built for longevity. I love the way mine performs.

 

Too much power or do you just want to be able to run pump gas?

 

Pump gas would definitely be more convenient for me since i can barely get 20 mpg right now lol. At this power level im always worried something is about to break. I know stock internals should be okay but i want this car to last for a long time.

 

If it's for the fueling that is totally understandable. But as long as you aren't detonating the stock engine should be able to handle that M62 fine. Also, not sure about what pulley size it happens but you could also be at the point where it could be beneficial to drop a pulley size or two to reduce heat generated and wasted energy without sacrificing too much power.