It's in the exhaust chamber for the number four cylinder. What's it's purpose? It looks like it's suppose to be there, but I can't quite grasp it's use. If it's normal, anyone who's seen this head will know what I'm talking about. I'll post pics in a few for anyone interested...


[Modified by 94gsr, 5:35 PM 8/7/2002]

 

Why can't I post these as images?

http://www.imagestation.com/mypictur...20with%20light


http://www.imagestation.com/mypictur...ithout%20light


[Modified by 94gsr, 6:31 PM 8/7/2002]

 

 

I jus6 looked at a 97 GSR head and it has it to. Ill look at a PR3 and check that one. never really notuiced it.

 

In case there is ever a need for an egr. There it is. Look at the intake manifold gasket. There is always a blackened area near the water hose by #4.

 

Correct, It's the EGR(Exhaust Gas Recirculation) passage. It takes a small amount of exhaust gas and re-burns it with your a/f mixture. It helps with emissions, but cuts down on power. I had the EGR system on my LS engine, however I removed the EGR valve and blocked the hole when I had the stock mani......I switched to a Skunk2 intake mani, which has no provisions for the EGR system.......thankfully.

 

I'll third that- it is for the EGR system that is not present in most of these heads. EGR reduces combustion temperatures and NOx emissions. It does reduce power but there is no EGR flow during WOT, only during high load-part throttle, so blocking it was not the greatest idea. The ECU reduces the amount of fuel injected during EGR flow and without the flow you will be running lean. This can cause detonation and damaged pistons, head, or head gaskets.

I believe the LS had an EGR valve with the automatic tranny (mostly and some 5 spds- possibly 50 state emission cars). The transmission adds heat to the engine and so an EGR valve was used to reduce NOx and detonation.

 

Correct, the car my LS swap came out of was an auto....thus the reason it had an EGR system.

 

Some newer engine managements can see the difference in the fuel and compensate here as well as during purging the charcol canister. Even so, the timing is still retarded during egr operation too.