Just put together a 331 stroker in my 1990 Mustang. Has a Holley Systemax upper end. Heads have guide plates and studs, comp stainless steel roller rockers, trick flow push rods and Ford motorsports roller lifters. Cam is a Lunati with .512 lift and 222 duration. Measured the push rods to assure the roller part of the rocker arm move in the proper range on the valve stem. This block has the Ford factory roller cam rev kit/hold down bracket. Aluminum Holley heads have been reconded and have 10 degree retainer and keepers with springs good to .600 lift. Piston to valve clearance is ok. My problem is a mometary tic-tic or a tap-tap or ping every 2-3 seconds. It is not constant. Can be heard thru the intake manifold.The valve covers have had the inside ground down for rocker clearance. Has good oil pressure.  Anyone have any problem with the factory lifter hold down bracket not holding the lifters in place, sticking or ? Lifters are new and have been sitting in oil until installation. Rockers are adjusted to index with 1/2 turn on the wrench. Need some sugestions on what to check...please
thanks rg  

I have the exact same problem. I have AFR heads and a cam with like 575 lift. Let me know if you find a solution.