EGR port size mis-match

[fumehappy]

Good morning,
So, I replaced my EGR valve. 1984 c-10 stock 5.0 Liter engine. Low altitude Emissions. Quadjet carb.

I pulled off the old EGR, and was surprised to find there was a riser plate beneath it. But then I noticed that the rectangular opening in the riser plate matched the size of hte rectangular opening in the engine, but the port on both the new and old EGR valves was about 1/3 smaller (as seen by the streak i made in the carbon residue) I ordered the new one based on engine size, not previous part number. Is this is correct? Also, the truck idles much rougher now, but smooths out with a little gas.
Thanks!

 

[Jarhead79]

Do you have all the smog stuff on there? If not just make a plate and eliminate the egr. Make sure you don't have a leak because that will make it run worse.

 

[fumehappy]

As of right now, all original factory smog stuff is bolted in place, possibly even functioning. My eventual plan was to leave the EGR as it supposedly improves mileage a bit, and delete the AIR system, while adding a new Catalytic converter.

Goal of the truck is to make it a restored solid driver.
Thanks!

 

[fumehappy]

Also noticed a decrease from 12 mpg to 11 mpg since the change. normal driving patterns and consistent fuel.

 

[fumehappy]

Update: yeah, your truck will probably idle rough if you leave a vacuum line off, and mis-route a second...