Originally Posted by Halfcent
Okay, yeah, I just learned that too.
So then the next question, what is there for? And why isn't it there on current production heads? And what if I put one with the passage on an engine that didn't originally come with one? And I still want to know why they have the same part number.
Whats it there for?? Its there because the head was designed with provisions for EGR(exhaust gas recirculatio, used to lower combustion chamber temperatures and the formation of NOx) in preparation for the possibility of certain engine/vehicle combinations needing this sytem to pass emissions. While Cavie states some early Saturns used it I personally have never seen any ECOTEC application with an EGR system, nor do any any of my service manuals mention one.
Why isnt on the current head?? Because it isnt needed/ wasnt ever(or rarely) used.
What if I install an EGR head on a non-EGR vehicle?? You'll just need to do what the factory did, block off the EGR valve mounting point with a plate. You might
(I havent measured) have some rad hose/thermostat housing interference issues on a 2006 car though as the thermostat housing has been reloacted slightly to right near the left rear corner of the cylinder head. Its much easier to service now(its previous location was kind of under the exhaust manifold at the end of the water pump feed pipe.)
Why do they still have the same part number?? Because they are interchangeable, and there hasnt been a need to change the number.
Good enough?? Anymore questions fgeel free to PM me.