Iv'e had a 56 Pan/Shovel for 18 years. Iv'e gone thru the engine three times but this last time is driving me crazy. I rebuilt the lower end (new pin, bearings, wrist pin bushings, timken bearings and pinion bearings) Trued it with dial indicators to .0005-.001 runnout and set rod end play to specs. Ground the seats and installed ss intakes & nitrated exhaust valves, the guides were tight and I replaced the oil seals. Checked the rockers and shafts (they looked great) and shimmed the end play. The cylinders looked good so I honed them and used cast rings. I installed a Sifton 512 cam that I got of eBay and set the end play to specs. Rebuilt the lifter rollers and used hydralic lifter units. Found nothing out of the unusual durring the tear down and rebuild. It had a lot of miles on it and I wanted to ride to Sturgis again this year, I try to go every 2-3 years and have gone 5 times without any major problems. It's had what seems like Bad rocker rattle ever since. Go up hill with a load on it and all is quiet like it should be. Go down hill or on the flat and it rattles like crazy. Real Scarry. I don't like going around the block let alone to Sturgis. So Far Iv'e: Checked rocker arm condition and end play (good) Checked the lifters and cam lobes (good) Pulled to whole top end. Bored the cylinders installed new pistons and cast rings. Installed A Ram Jet rocker arm play kit. Pulled the hyd units and installed a Sifton solid lifter kit. Checked the timing and replaced the old manual dist with an auto advance unit. It rattles the same hot or cold and nothing Iv'e done has changed it one bit. Could the cam do this??? I never had this problem before the rebuild but I can't see why it would. I checked the cam with a dial indicator when I got it and it did have a little more lift and duration that my old FLH cam, But nothing that radical. Iv'e been building my own engines and worked in the shops doing the same for 35 years but this has me stumped!! Sturgis is getting Close!