i've changed my cam timing on my SOHC a whole tooth and it didnt change much...certain ECU chips i try have the timing advanced too far and to counter this, i had to retard the cam a tooth. It loses a little bottom end, but it sure rips ass in the top end. Sometimes, you can check if its off a tooth by checking your ignition timing. If the cam timing is off, you can advance or retard the distributor all the way, and it still isnt in time.