I know it seems like, when you're putting studs in, most of the 24v's with SO pumps are bottom tapped but it seems like a lot of 24's with HO pumps aren't. What I'm asking is, when I put studs in my 12v, will I have to tap the block or, are the 12v's already bottom tapped?

 

On the 12 valve don't know about bottom taping but you will have to machine the rocker pedestals.

 

I had to bottom tap both my 12 valve and my 24 valve when I did them.