Need help to find my engine rattle problem. Engine was in truck when I purchased it and it had been setting for years however it was not stuck.I have s/n 053322IF255P 235 engine with a rattle at cruise speed. Timing is at 5 degrees with 18 inches of vacuum. Starts, idles and runs good. When I get to cruse speed a rattle developes. Give it fuel or let off and it goes away. The oil pressure is 15 pounds at 180 degrees. Thinking spark knock I retarded the timing to 0 however I could not hear any change. Thank you for any guidance.
