do i new a 3 inch dp

[gpgt2002]

This is kind of a dumb question but I keep going back and forth. I have ported front and rear manifolds, hv3 insert, 180 t-stat and a few other things i can't remember. Do I need a 3 inch dp or am I fine with a 2.5 dp

[TheOtherNick]

If you all ready have the 2.5 stick with that.

[cerick08GP]

^^ X2

In my reading here and many other resources N/A engines seem to in general like a bit of back pressure. Unfortunately it seems to be a magic un-documented value for literally each car. IMHO you seem to have already achieved a good setup, going to super low restriction setup many not net you any gains.

[blueguy]

Unless your going to put a ported TB, rockers, or a cam...then just keep whatcha got...although the 3" will flow a bit more, but probably not enough for you to notice.

[gpgt2002]

thanks

[chico]

You do mean that you have an aftermarket 2 1/2" DP I hope and not a stock 2 1/2" OD DP ?

[killakross5o4]

i have a 3 inch DP from zzp 304 ss if u decided u want to go 3 inch

[GTPJOE90]

i got a hogan racing 3 inch catless u bend less dp listen to killa go 3 or nothing

[killakross5o4]

i got a hogan racing 3 inch catless u bend less dp listen to killa go 3 or nothing

i have headers now.... i am offering to sell him my 3 inch zzp u bend delete downpipe

[gpgt2002]

i bought a new zzp 2.5 cat dp and my buddy was tellin me i needed a 3 but i wasnt sure because its a gt but eventully ill get a 3

[blueguy]

2.5" isn't BAD for an N/A car...someone will probably bring up backpressure needed blahblahblah...but 3" won't hurt it either...it'll just especially help with the flow when you get more valvetrain mods or other meaningful bolt-ons...like a blower