2.5" or 3" Y-pipe??

[Bad Habit Bird]

I just bought some coated hooker longtubes and a gibson catback for the truck and right now I am debating on whether I should put a 3" or a 2 1/2" y-pipe on when I take it to the exhaust shop.

It is a 96' Ext. Cab Z71 with a Vortec 350 on 33" tires and 3" of lift with no mods other than the exhaust I will be putting on it. I will be putting a new water pump and a hypertech thermostat in it this weekend and a K&N Intake on it in a few weeks, and that will be it as far as performance mods go.

The truck is mainly just a daily driver and will be towing my Formula to the track occasionally. With that being said can anyone give some input on what size I should go with?

[Bad Habit Bird]

OK I know I'm new here but can anyone give me any input on this subject?

[cravnpup]

I'm assuming you have a single cat. If so, I'd recommend the 3" Y-pipe to a 3" cat to a 3" catback...

[Hit Man X]

A full 3" exhuast will be too large for a pretty much stock 350. I'd do with a 2.5" y-pipe into a 3" collector, 3" cat, and that Gibson.

I thought that those body trucks like yours had true dual 2.5" pipes from the factory?

[97Silverado]

Originally posted by cravnpup
I'm assuming you have a single cat. If so, I'd recommend the 3" Y-pipe to a 3" cat to a 3" catback... 350s are dual cat, 305s are single cat.:read:

[Hit Man X]

I thought so, my old 1996 2 door Tahoe had true 2.5" duals so I assumed the same for the trucks...

[Bad Habit Bird]

I currently have a dual cat setup on the truck now (Factory) I dont plan on putting cats on it when I first put everything together but I will end up getting two cats put on it sometime in the near future.

I'm thinking the 2.5" will help with low end torque for towing as well.

[97Silverado]

Originally posted by Hit Man X
I thought so, my old 1996 2 door Tahoe had true 2.5" duals so I assumed the same for the trucks... Well, even from the factory they had dual cats but a single muffler.:read:

[cravnpup]

Originally posted by Hit Man X
A full 3" exhuast will be too large for a pretty much stock 350. I'd do with a 2.5" y-pipe into a 3" collector, 3" cat, and that Gibson.


errr, isn't that what I said?? When someone says a 3" Y-pipe I would assume that it's in reference to the collector size (i.e. dual 2.5" inlets to a 3" outlet).. Anyway, why would you even need a Y-pipe if you've got dual cats?? Why not just run a dual inlet muffler, or true duals?? Doesn't make much sense to me.. That's why I automatically assumed he had a single cat...:whatever:

[Bad Habit Bird]

The Gibson catback I have is a single 3" inlet with dual 2.5" outlets. That is why I am having a y-pipe made.

[cravnpup]

Oh OK... That makes sense.. So like I said before I'd go with the 3" Y-pipe (meaning 2.5" inlets to a 3" outlet)...