Need some help trouble shooting a tappet like sound coming from the front of the engine. The noise sounds just like a tappet. I just changed the #12 heads to ported 722"s. I put in a comp cams hyd. roller #cca-51-433-9. It didn't make the noise before I changed the head-cam combo. I used a stetoscope to find the tappet sound and it is located in the front of the block and a lot less in the rear of the block. Slight noise in the timing cover and fuel pump area. It's the same on both sides of the block and on the front of the vally pan. No tappet like noise in the bottom end. Things that I have checked--correct lifter installation, rocker arm geometry, push rod clearance,lifter clearance,spring coil bind,valve adjustment,lobe to block clearance,piston to valve clearance, cam timing, correct thrust plate bolts, I tried to put a .010" feeler guage under the rocker to to rule out a bad lifter but it wouldn't go in, I have looked at the timing gears, timing cover, fuel pump, valley pan for any type of scraping. Any motor heads out there have any ideas where to go from here or what else to check. Sure would really appreciate any advice guys.