Timing at 34* full advance at 3000rpms, shoot for around 14* base timing, but let it fall where it may.
What ignition do you have????
Spark plugs, AC MR43T or NGK BR6FS gapped at .035-.040
800cfm Holley carb
What failures did you have in the other engines??????? 4 blown engines with less than 4 hrs each sounds like a set up problem. Plenty of people have run 1800runsnew engines with good results.