So the Eclipse engine has a different head? Is this for reliability or other reasons? Also is the compression the reason for the different horsepower between the Neon(150) and Mitsubishi(140) engines ? Also why waste the time putting the 2.4 in there if it only has 1 more horsepower (141), better tolow end torque maybe? Just looking for some insight and info not trying to irritate anyone. Thanks for the info.

DOHCs are for power and efficiency, the better an engine sucks the better it blows and vise versa. DOHCs are more expensive to produce.

Compression actually doesn't vary much from one modern gasoline engine to another, compression is however effected a small amount by the valve train; the cam in particular.

Let me help to put HP and torque into perspective for you. A popular 18 wheeler engine and a personal favorite is the "4 and a quarter CAT". 425 horsepower, not much for lugging around 80,000 lbs is it? On the other hand it makes about 1400 ft/lbs of torque, the catch to that is that's at about 1250 RPMs. Arguing about torque and horsepower is like comparing defense and offense in football, the truth is a good balance is usually the desired result. Since we're talking about 4 cylinders here, even a small gain in torque can make a huge difference in power. This is because they only produce about as much torque as the lug nuts require to begin with haha.

Roller stakes vs Stake broads = Neon vs Eclipse.