Okay, so now I have the longtube hookers instead of the SLPs (some of you might have read my post about the angle plug heads). I was on the phone ordering the mean mufflex ypipe, and told the guy I needed to weld up my SLP catback to the end of this (4") ypipe. I bought the $25 adapter piece to neck the pipe down to fit, and the guy asked me how much power I was expecting. I told him right at or just above 500 flywheel HP, and he told me that the 3" was really going to hurt my performance. Does anyone have a guestimate as to how much power loss I will experience using my existing catback or was this simply a sales pitch to purchase their $500 catback? I plan on going to their full 4 inch setup someday of course, but for now I'm kind of stuck with what I have.

Some important mods are as follows...
355 4 bolt 2 piece rear main seal
Forged rotating assy,
Holley Stealth ram intake
Lingenfelter 58mm Throttle Body
SVO 30# injectors
Air Flow Research 195cc 68cc chamber, 10:7:1
NO EGR
Cam…lift is .560 at the valve with a 1.60 rocker which
Equals .350 lobe lift lobe sep is 110 intake centerline is 106
Degrees and duration at .050 is 224 degrees for both intake and
Exhaust
Hooker Super Comp Long tubes, ceramic coated
Mufflex 4” y-pipe
No cat
3in. SLP exhaust
Flowmaster 1 chamber
GM 1991 Firebird speed density wiring harness
GM ECM # 7730
150 HP wet kit nitrous
~500+HP + n2o

 

I think it was just a sales pitch...my friend has a 01 WS6 with a 432 ci LS1 with a 3 in cat back, and his car runs in the 10's. I don't think that you will have much of a problem. The 4" could help, but I think you will be just fine with the 3".

 

Great, those were my thoughts exactly! I do belive there will be a power loss involved, but not enough to justify a $500 upgrade. The horsepower per dollar ratio is not good enough to justify the swap at this point. Furthermore, your friend's 432 makes for a much bigger airpump than my 355 cubes. I plan on just turning this motor to 6-6.2K max because of the hydro rollers.

 

g o d damn a 432ci LS1 ? you could tow an 18-wheeler with that :sillylol:

 

Yeah, it has over 500 rwhp...he is taking it to the dyno soon, I'll post when he does.