I just got done installing my long tube headers on my 01 ss . The LTare followed by dual magnaflow cats and go into a flowmaster ''Y'' collectors with dual 3'' inlets and 3.5'' outlets followed by 3'' pipe into a flowmaster muffler and dual, dual pipes. Would I loose HP or TQ if I was to follow the 3.5'' collector with 3.5'' pipe into a dynomax ultra flo Round 21'' long or a borla xr-1 12'' long even a magnaflow all 3.5'' with a turn down in front of the axle. I really don't whant a flowmaster type sound, I'm looking for deeeeeeeeep mellow.

 

your description is a little confusing. you say you have LTs with 3" collectors, into a 3" ypipe that joins into a 3.5" outlet. then connects to a 3" catback?

what other mods do you have?

going to 3.5" exhaust from the Ypipe back probably won't hurt you. maybe a little drop in low end power...but probably only under 2500rpm.

i know i noticed a nice gain with my LTs, 3" ypipe, and a bullet muffler on the intermediate pipe.

but it won't be a deep mellow sound. it wil be a loud raspy sound. nature of the freeflowing, very low restrictive, minimally muffled setup.

 

Sorry about the description, I was half asleep last night when I wrote it. The collectors on the LT are 3'' the Y pipe being the same, it turns into a 3.5'' because I used a flowmaster part called '' Y collector " witch has dual 3'' inlets and a 3.5'' outlet from thereI simply hooked it up to the original pipe. Not sure if 01 ss cars came with 3'' catback or it was added by the previous owner.

 

you shouldnt lose any power with that setup, although i don't think there is anything to gain either.

a 3" setup flows well enough to support a bolt on LS1 with minimal lose in power.

and like i said...that setup...no matter what muffler you use...will be LOUD

 

I disagree. Even bolt on LS1s can see a noticable gain going from a 3" catback to duals, so the 3.5 should help.

I'm running a 4" mufflex catback.