Some people claim they can hear a difference, but I've never noticed it on the engines I've built. Of course, I grew up building flathead Fords, and there was no choice- - - -cam gears were all made of aluminum. There's a little bit of gear hum from both, so unless you've got very sensitive hearing just pick whatever suits you. My hearing got sacrificed to B-52's, race engines, and deer rifles years ago!
Jerry
