Anti siphon valve

I am redoing the fuel system on my 72 Mustang because the motor acts like it is starved for gas when I am running it hard. I believe there is what is called an anti-siphon valve on top of the gas tank that feeds the fuel line. I can't believe how difficult it is to manually open this check valve. Is it supposed to take extreme force to open this valve? Will any part work as a replacement or is it tuned for the specific fuel pump? I am considering running the boat without it to see if this is the problem but don't want to discard a perfectly good check valve if that is the way it is supposed to work. Any insight is appreciated!

Anti siphon valve:

onebigdog wrote:    If I push on the bottom tappet .

"bottom tappet" ?   

KENO wrote: Don't mind Pete's reply, if you don't speak in Pete terms he'll question your terminology and act like he doesn't know what you're talking about.

Ken,
Please explain to me what he's referring to and what a "bottom tappet" is.

8122pbrainard wrote: KENO wrote: Don't mind Pete's reply, if you don't speak in Pete terms he'll question your terminology and act like he doesn't know what you're talking about. Ken, Please explain to me what he's referring to and what a "bottom tappet" is.

If you can't figure out what he meant by what's already been written Pete, it would be a waste of my time and effort trying to explain it

8122pbrainard wrote: KENO wrote: Don't mind Pete's reply, if you don't speak in Pete terms he'll question your terminology and act like he doesn't know what you're talking about. Ken, Please explain to me what he's referring to and what a "bottom tappet" is.

Ok Pete, I’ll take a stab at it.

A priest and a rabbi are drinking at a bar and in walks Honor Blackman. Priest says to rabbi “I’d bottom tappet”

Or it’s most likely the ball inside the valve?