Guys, I have read a hundred posts on here about the Noise in the Comp XE274 cam. I just had a 396 built with one of these cams and it is making a really bad noise in the top end. From 2500rpm to 4000rpm same noise just louder. to the point were you would just turn away for fear of what might come flying out of it...LOL
We put new lifters and went from full roller rockers to roller tips. Made it a bit better but not much. So the shop decided to pull it out and take a look.
IN doing so found nothing wrong in the bottom end.... perfect thats eliminated... so here is a cut down version of what was found.

1.)The roller tips had some blueing on them.?????

2.) The stem of the valve was "dented" for lack of better terms or I guess it shows wear...??

Has anyone ever experienced this before????

I would look at the valve spring set up, if you have blueing, you have excessive friction....

I bought a small block once as a place to start for a rebuild. I took the heads to a machine shop and they told me all of the valves should be replaced. I went to the shop and looked at them and they were deformed by the roller tip for two reasons: Improper pushrod length and weak valve springs. The guy who built the motor had a pretty big cam in it with stock springs. They told me that it was caused by the valves "bouncing" due to weak springs and hammering on the top of the stem. Add to that the fact that the roller was riding toward the edge of the stem and it cost me a few dollars to fix.

Scott ,what year is the block ?
'65-'66 need the rear cam bearing surface grooved for proper oiling along with the grooved bearing itself..

The block is a '69 and the correct bearing was used.