Fulcrum Rocker Bolts

[federal officer]

So I broke one of the bolts that hold my rocker arms. (long story) So my question is, are they a specific type of bolt ? Beacue I tried to find a replacement at the hardware store and nothing would work. I was told maybe it has a very specif pitch that will only work for that application I tried metric and standard. Its a stock 1985 GT h.o

 

[4G-KDMP]

The bolt is 5/16 -18

 

[federal officer]

thats what I thought but it wasn't working at the hardware store. the bolt was stopping at the tip. i thought it was weird.