[3150Mach1]

Originally Posted by Boss 330

This thread makes my head hurt. The tick was/is caused by excessive stem to guide clearance, end of story. The guides had too much clearence right from the start. This allowed the valves to hammer back and forth in the same plane as the followers. The guides would wear into a oval shape. This movement scrubs the valve on the seat and the valves soon lose the ability to seal. Low compression is the result.

Most all of the new replacement heads sold over the counter had the same problem. Ford specification was .002 max stem to guide cl. the brand new heads were .004-.005+
Also..Piston slap gets worse as the pressure goes up. When the thrust transfers from one side of the skirt to the opposite side of tdc that is where the rattle comes from. This gets really ugly with the big piston to wall clearence some builders seem to like. We tore down a 4V this week and had a suprise.
The owner stated the oil fumes were making him sick. This thing had a few thousand miles on the rebuild. The engine had .020 over pistons in a .030 over bore.

Some pistons have pin bores offset to help reduce the slap on cold starts. Many new engine designs have the cylinder bores offset in relation to the crank centerline.

You are the man Al.