Best way to remove this?

[Clunthoo]

Hello,
I am messing about with this image of a caterham, changing colour of stripes, mud guards etc. But where the engine is, it has like 50% opacity. I was wondering what the easiest way would be to make it so you could see the engine clearly. The slow and hopefully isn't the only way to remove it I was thinking is to go over it with a brush in the colours of the engine, fuel tank etc

 

[hawkeye]

Copy the red channel to a layer. You'll still need to clone/paint, but it should make it a little easier.

 

[stufflol]

quick one i did

 

[Stric9]

I don't think there is an easy explaination on how to remove this completely. I used many levels/hue saturation stacked and masked and then the clone stamp primarily.