EGR Valve differences?

Discussion in 'Engine Topic' started by Michael211_2000, May 23, 2011.

  1. FS87LT

    FS87LT New Member

    Apr 3, 2010
    DFW, TX
    Two EGR valves, or more, will look the same externally, BUT they can have different sized internal restrictions (related to EGR volume) and different springs for timing of said flow.

    The main differences between an LT and a Z/28 have to do with the rear axle ratio and tire size. The Z/28 automatics had 3.42 gears and the 4-speeds had 3.73s. Not to forget the exhaust system differences (dual outlet muffler on the LT and dual resonators on the Z/28s. The tire size on the Z/28 was GR70-15 (now P225/70R-15) and the LT had smaller 14" 70-series tires.

    In reality, I suspect either one would work well and you'd not know which was which, except that there might be slightly different readings on an emission tester at registration renewal time.

    The TPS switch which runs the EGR valve runs off of ported vacuum, not manifold, I suspect. The temp spec on the TPS keeps EGR from happening with a cold or warming-up engine. IF it ran off of manifold vacuum, the EGR would be either full open or closed, which would not be good in all operational modes. Either way, it should be closed at WOT.

    Many aftermarket EGR valves will come with a set of washers/flow restrictions. For a particular engine size, you'll insert a corresponding colored washer to "customize" it to the size of engine it's installed on. Better to get one which is designed and calibrated for the particular application than adapting a "will-work" item. When possible, going by the "stamp number" on an OEM valve is best. Part numbers can and do change, though, which is why GM parts usually referenced stamp numbers in the parts books.


Share This Page