help, question about o-ring under the 3rd bridge cam holder.
 

http://www.c-speedracing.com/h...9.jpg

you guys see that o-ring in the middle? my friend saw my motor and said he didnt have an o-ring there when he put in his new cams. he hasnt noticed any problem(s) yet. is this o-ring for oil flow? how important is it? he doesnt want to take everything out again for that o-ring.