I have a question about removing the egr valve on a 91 chevy 454 in a one ton dually. I need to remove it to replace the valve cover gasket. my problem is this: a 13mm is too big, a 12mm too small. a 1/2 inch is to big, a 7/16 inch is too small. my question is what do you get the nuts off with? I really don't want to pull the intake over a valve cover gasket. do I need a special tool? any help is appreciated and gratefully accepted. thank you

1991 chevy Silverado c3500 extended cab dually
454 auto rwd

 

Likely a factory tool to keep people from blocking the EGR valve by making some offsize tool. Maybe MAC would have it, but i'd be $$$$

I'd either chisel it off, or buy a real cheap wrench at Harbor Freight, and grind it down until it fit the nut. That is if it doesn't strip- out, as those tools are made in China and not worth much. If it works great, If not you are not out much $$$.

 

You could try a nut remover tool.

 

You are absolutely right, oldchevy!.