what are the contributing factors that lead to excessive carbon build up?

I noticed that on my D15 motor (I just got this car) that the valves has a wicked thick layer of carbon on them yet my D16A6 and my B18C5 Si motor is perfectly clean ?

I plan to use GM Cleens to clean the crap out and seafoam to clean up the motor afterwards....

Suggestions?

Thanks

 

its from the gas,,carbon is in gas..and all that **** on the motor is from unburned gas and the additives in gas...it isnt hard to clean but it will keep coming back

 

that's what I figured. The previous owner donated his car to me after I told him how much it was going to cost to fix his car. The vehicle has 330, 000km's the cylinder 3 exhaust valve was so burnt that it was missing a large chunk of metal. I just finished replacing the head tonight but I want to make sure that the carbon doesn't come back the way it did on the original head. Strange that my D16A and my B18C5 hardly ever have carbon. Mind you my cars are always tuned well and cared for. This new EF I got had red rocker arms from the oil being burnt up in the head.

In any case now that I'm the official new owner I will spend some quality time restoring this EF sedan. 330, 000km's with an auto tranny. Body is in okay shape considering the mileage. It will be my winter car so my beloved CRX won't suffer the fate of rust.