I dont think you'll see very much gain going to 3.5 personally. I ran 123mph through full 3 inch exhaust with no cutout and MAC headers with 3 inch Ypipe. Grotts with 3 inch YPipe into 3 inch cutout into 3 inch int pipe into the rest of your exhaust will work fine IMO.
Cheers,
Chris
ps- Dont forget a couple of 422s made 500RWHP through crappy MAC headers and the STOCK 2.5 inch Ypipe. Nineball lost a bit of torque and HP going to his new setup but hasnt tuned it fully yet.
pps- check into the 230/230 cam ARE has now, it is making GREAT power on several cars. If you want added exhaust duration go 230/236 on their new lobe on 112LSA.
4.10 gears would also help move out your heavy sled alot too. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

<small>[ August 26, 2002, 02:16 PM: Message edited by: Chris ARE 360 ]</small>

 

Your wasting your money,I was gonna do an X setup or something trick,But I decided to stick with my 3in Y to my SINGLE 3in inter. to my 3in SINGLE 3in tail w/3.5in. SS slant cut tip.

Its light and flow serious CFM,Im gonna try to run the car threw the full exhaust like Chris did just to really see how much I lose...

JS

 

Thanks Chris.

I keep my cut-out back just before the turn-up to go over the axel. I like keeping the noise and exhaust fumes away from the cabin.


On longer highway cruises, I miss my 3.23s, so no 4.10s for me. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
I left a message for Nick about 5 minutes ago on the cam. 230/236 112 is probably going to be too much for me, although I was surprised by how tame Black Sunshine says it idles.

 

Since the grot Y-Pipe is a POS, I'm going to make a new Y-pipe with 3" pipes into a 3.5" collector. My options for after the Y-Pipe collector are:

1) run 3.5" pipe for 2' then a reducer to 3" pipe and into my 3" QTEP cutout, with 3" going over the axel for my SLP D/D
OR
2) run 3.5" pipe and buy a new 3.5" QTEP cutout, then into a reducer to 3" for the pipe going over the axel for my SLP D/D.

Bottom line: Is it worth buying a new cut-out and QTEP to run 3.5" pipe?? For purpose of this analysis, I'm assuming this will add a little over $200 for parts & labor. FWIW, I would do the 3.5" if I were starting from scratch so I'm leaning in that direction.

Car details in sig. Cam will probably be upgraded to something like a 228/232 and will be shifting above 6600 rpm.

 

If you do the flow number calculations you'll note that a 3.5" pipe will constrict the flow of two 3" pipes. Personally I'd recommend going to a single 4" I-pipe for max power.