Small Block & Big Block Chevy Specific - SBC pulley bolt sizes

dumb question but I can't find them anywhere, does anyone know what size the water pump and balancer pulley bolts are? I've gone and just bought everything I thought would fit at HD and come close, but nothing seems to fit quite right :bang:

I thought maybe the parts stores would carry them in some sort of dress up kit but no dice. While I'm on the subject, I can't find a fitting to fit a stock mechanical fuel pump outlet, if anyone happens to know what size/type it is, looks like an AN fitting but nothing I've tried fits there either.

1/4-20 or 5/16 i don't remember

1/4-20 or 5/16 i don't remember
Huh, wonder what's up then, 1/4 is too small, fits right through. I tried to push a 5/16 through there and it just chewed the threads up on the bolt.

the w/p BTW is a jegs short nose, I thought they were just reman OE pumps, maybe it would be easier to just drill out the threads and tap it with a known size.

I looked last night, its 5/16. Did you try fine thread of corse? you could try cleaning the threads with a tap, but I wouldn't redrill the holes or you may have problems with the pulley.

I looked last night, its 5/16. Did you try fine thread of corse? you could try cleaning the threads with a tap, but I wouldn't redrill the holes or you may have problems with the pulley.

I think it was a coarse. I'll try a fine and I'll chase the threads.

thanks for looking! appreciate it!

this thing is KILLING me :)


I tried some more 5/16-18(?) and it's just not the right thread, I even tried the nearest metric with no luck.