According to my manual, they are interference engines. In the timing section, this is what it says:
CAUTION: Do not rotate either the crankshaft or the camshafts when the timing chains are removed and the cylinder heads are installed. Severe piston and valve damage will occur.
This is what is listed for the 4.6L and the 5.4L. So, yes, they are an interference engines.
Thursday, September 25th, 2014 AT 6:48 PM