I know this isn't a Camaro, but I need some help. I have a 93 Buick Roadmaster with the 5.7 LT1. The egr valve has serrated head bolts that look like E drive bolts. Does anyone know what size head these bolts are? I have an engine code 32 and I want to remove the valve for inspection purposes and possible replacement. I have some ignition wrenches, but even those are too large. It may be a 13/64" or 3/16", but they have to be 12 point. I am not sure because the whole car seems to be metric. Any help would be appreciated. Thanks.

The bolts on that EGR should be inverted torx, but I,m not sure on the size you need.

I just got back from the dealer and the thread size for the stud listed was 5/16 x 18. I tried to put a 15/32" wrench on it and that was too big. How can the wrench size be smaller than 15/32" and the stud thread size be 5/16? That is impossible.

If the stud size listed is 5/16 then it cannot be metric. Try a 7/16 eight point socket.

Frank, I meant to type 15/64" and that was too large. The dealer has the thread listed as 5/16 x 18, but that is impossible. If the thread was 5/16", then the head on the nut has to be at least 21/64" I used a 15/64" ignition wrench on it and that was too big. I don't know what else to try. I can't use a socket because there isn't enough room for that and your ratchet. Maybe a crows foot, but where are you going to get a crows foot that measures smaller than 15/64"? If I could find a wrench that was 7/32" or 13/64", one of those may be it, but I have never seen a wrench that small.