Okay, check this out. This picture is from Patriot Performance Heads web site of an L61 engine cylinder head:


And this a very quickly photoshopped picture of the same head:


Heres another picture of it taken from the build book;


Now the first head has that cast-in coolant cross over passage and it is used in L61 ecotec engines from 2002-2004. The second picture is the head used in ecotecs from 2005 an on, without the cast-in passage.

Here's my questions; First, why do they have same part number? I just got back from a Chevy parts counter and we looked up a 2005 cobalt and 2003 cavalier, and the cylinder head part numbers were identical. Second, despite the difference, are they compatible?

I ask because I obtained a core engine from a 2003 Cavalier to use on my 2005 Cobalt, and we discovered the difference in the head castings just last night. Any info that anyone has is greatly appreciated.

 

I wouldn't think there would be any difference anywhere else in the head, I think you should be ok. But don't just take my word for it, do the math and compair the measurements on both heads to see what matches and whats different.

 

that isnt a coolant passage

its the EGR passage

some early saturns had EGR , that is why that V is there

 

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.

 

Thanks dude.

 

New question on the same topic. Does the GMPP head have the egr casting? The picture I posted above from the build book doesn't show one, but I would like to be sure.

 

Even if it does, I don't see where it would interfear with anything. Just get the block off plate that sits on the top. I can get the p/n of that plate for you if you need it. Just PM me I will look around.

 

You might want to check the stock exhaust manifold on your Cobalt man. The only reason you need a block off plate is if the manifold has a flange extension to route exhaust gas to the EGR passage. If that extension of the flange is missing from the Cobalts you don't even need to worry about it.

I've been under my hood plenty and haven't noticed such a passage... I might double check tommorrow. You might have to pull the heatshield to get a good look. 3x 13mm bolts and its off.

 

No, no, you misunderstand. I know the EGR casting can be simply capped off and I know the Cobalt doesn't use it and in fact doesnt even have it. The problem is the even though the casting is not used, if it cast into the head, it won't fit inside the engine compartment. The Cobalt routes electrical and plumbing lines in that space and you will result in an interference fit. I would rather buy a new stock head and port and polish it then get the GMPP head and find out afterwards that it has the casting.

My question is simple, does the GMPP head have it or not?

 

best thing would be to call GM about it and ask, no?

 

Bandsaw anyone?

 

Do you actually believe a telephone customer service rep would have any idea about this kind of question? Actually I was thinking about calling Bates Engineering, I think they actually make the part for GM.

And, actually, you can cut it off, but then you have to weld the hole closed, and I don't want to weld a high tolerance cylinder head like this one and warp the **** out of it.

 

It was just an idea bro.