I have a 2004 Ford Ranger 3.0 and runs rough at idle and will miss idle in park or neutral , runs great highway . 2 years ago I installed a “ roll over “ junkyard engine and when got it running had miss with low compression 4-5-6 . Removed head and valves sucked in . Put my cylinder head from original engine on replacement engine and ran perfect about 2 years and now same issue . Would it be advisable to replace all valves on cylinder heads that I pulled off junkyard engine ? Is there a stamping on cylinder heads where valve seats are an issue and best to just replace heads . Please Advise

 

Welcome to the forum

Yes, Ford sent out a TSB for 2004-2006 3.0l engines, but can also effect 2003-2007
The exhaust valve seats were the issue not the valves but the valves would get burnt from escaping gases when the seats recessed into head, and of course that caused lower compression in effected cylinders

These heads can be rebuilt with new seats and exhaust valves, the head itself is fine to use, assuming it wasn't overheated and cracked, lol
If on a budget you could probably just replace exhaust valve seats and exhaust valves and leave intake valves and seat as is, but I would just do full valve job so no doubts


There are two different heads for the 3.0l, they have different shaped chambers, one for gasoline only and the other for Flex Fuel, you can use either SET on any 3.0l Ranger engine, but NOT one of each
Picture here: https://www.therangerstation.com/tec...3.0build11.jpg
Left is for Flex Fuel, right is gas only

There was also a change in valve stem sizes, not valve size, valve stem size in 1999 and up heads