Can someone explain what this is supposed to do..? I see .471" and .500" ones advertised, but I'm not sure what they do, and if bigger really IS better in this case?

 

The larger the # the more line pressure there is, creating firmer shifts.

However, most tranny guys will say on most str applications to go with the .471 boost valve.

 

Hey Ken. I've got a .500 main boost valve and a .283 reverse boost valve. When I had the B&M shift kit it was painful, but with the TransGo shift kit it's very liveable on the street.

I would get the bigger valves now because you know you're gonna want them later

 

.471" is the largest GM makes. .500 is aftermarket. The .500 boost valve is pretty much as high as you want to go. I have seen up to .577" and that is just overkill. You want the tranny to shift firm, not bang into the gears.