Hey guys,
On my chvy 350 block located between the 6 and 8 cylinder, there is (was) a plug (bolt) I removed during my motor cleansing and areosol overhaul. I didn't put it back in and dont have it anymore. It screws into something already screwed into the block, it looks like a reducer. Anyone know what I am refering to. I need to know the size the bolt to go back in. I bought a 1/2", too small, 9/16"?

Thanks

Here is a pic...

its a pipe thread. i beleave its npt not sure on the size go to any decent auto parts store and they will know the size. a brass plug will work.

1/2" pipe thead.  Go get a plug at home depot....or if your local, I've got about 20 of 'em.

Pipe thread IS different than bolt thread.  Pipe thread is tapered and the sizing is based off of the inside diameter of the pipe, so a 1/2" pipe thread fitting is going to have an outside diameter closer to 13/16"

3/8" npt is a little over 5/8"
1/4" npt is a little over 1/2"

Hope this helps.