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Hole in my EGR passage


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Above idle and below full throttle the EGR is active and mixes small amounts of exhaust in with the intake air and fuel. The exhaust is inert and oxygen free and simply takes up space in the combustion chamber. This lowers the power slightly, but more important it lowers the oxides of nitrogen emission causing combustion temperatures. This only works if exhaust without oxygen is used. If you have a hole in the tube outside air with oxygen will get in and upset the intake air / fuel ratio designed into the carburetor. Effectively you will run a lean mixture during EGR operation. 


If this is on the 620 try wrapping with that one sided sticky aluminum muffler tape to seal it up.

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Sorry guys, I am working on a 74 620.


Thanks again Mike, I will pull it out today and see if I can wrap it with the muffler tape. I have been doing research on here and came across some info on making an EGR block plate. Seems that everybody has a PVC holes going to the EGR passage area, but I don not remember seeing one on my truck. I know you mention on other threads how important it is to have one.

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