454, 1987, lower oil dipstick Bolt

[Sgt Gus]

Bolt at the block is missing, and haven't figured out.
Google AI says 1/2" - 13, but no.
The power steering Bolt on front of water pump is that size.
Definitely seems 1/2", but finer thread.
Could be 1/2" - 14 npt, but that is pipe thread?
1/2" - 20? Seems to fine, but clearly I don't know.
Can't hurt to ask men. One damd Bolt.

 

[legopnuematic]

Got a photo?

I'm not a big block guy but a 1/2" bolt sounds rather large for a bolt on component. I'd suspect 3/8-16. Thats what (on small blocks at least) is used on the water pump/brackets.

 

[WFarm]

1/2-13 is coarse thread. 1/2-20 is fine thread.

 

[Ricko1966]

I imagine it's 5/16 18 which would be a 1/2 wrench size.