Head Dowel Sizes 6.0L PowerStroke® Diesel
Not sure what size dowels you need? This should help you.
18mm head dowels were used from Model Year 2003-2006.5 and had casting numbers - 1843080C1 thru #######C4. Example: a 2006 Model Year truck that was built in 2005, came with 18mm head dowels from the factory.
20mm head dowels were used for Model Year 2006.5 & 2007 with the casting #1855613C1. The rocker box bolt size and location changed, along with the fuel injector holddowns and are not directly interchangeable with the components for the earlier 18mm dowel engines.
SRH (Service Replacement heads) Dowels
SRH (Service Replacement heads) these heads are a 20mm head dowel casting #1855613C1, but the top is machined to use the earlier rocker boxes and injector hold-downs from the 18mm dowel engines. These were made by Ford for use on the earlier engines that needed heads replaced after they had switched production to the newer castings. These heads are the intended use for the 18-20mm stepped dowels, since they have 20mm dowel holes, but are supposed to mate to a block with 18mm dowel holes.