white1

iTrader: (5)

Ive been thinking, I maaaaaay go dual, but I can eigther get the Thorley's and a converter Or the Pacesetters and Y pipe, or just the pasesetters. I dont think Im gonna have enough mods to truly need duals with this motor anyway. Even in the future, I may just step up to 3.5 single if my plans fall out how I hope they do (408 )

SCIV

iTrader: (7)

I have Thorleys with the TR224, and I like them. I still run cats as well.

hog

I think a single 3.5" exhaust would truly work well. I think that having all the exhaust come together after the headers helps with all around torque and power. This is why X and H pipes work.
All the air passes thru 1 MAFS and 1 throttlebody, it makes sense to have all the exhaust come together in the exhaust at some point. Having a single exhaust, or a Y-pipe or an X-pipe makes the V8 engine work as 1 unit rather than as 2 seperate inline 4 cylinder engines.
I used to think that the less backpressure the better on the street, until I unhooked my exhaust and ran open headers for a few minutes. the lack orf low rpm torque was astounding, it sounded cool but it was a dog. No backpressure may work well with race cams, but with a street engine, using the exhaust to tune the power bands is a much better approach.

Having dual exhaust sounds cool, both audiably and when bench racing, but I dont think true divoreced dual exhaust from the headers to tailpipe is as effective for power and torque production as either a dual exhaust system with a, x- or y- pipe or a single exhaust system. Bigger is not always better.

Thoirley Tri-Y headers are a good set of headers, they connect certain cylinders in an attempt to use the V8's firing order to increase scavenging(the process of using the spent exhaust's momentum to draw the next fresh air/fuel charge into the cylinder).
Gains will be felt in ALL rpm ranges when compare dto a stock exhaust system, but the tri-y design will bolster low rpm and mid rpm torque and power. The design is GREAT for trucks and any street going vehicle that relies on torque at many different rpm levels.
On the OBS 96-99 Vortec 350's the Thorleys were a mid length design and headpipes(pipes from collectors to cats) were included. The stock headpipes were generally restrictive for supercharged engines, but were a big improvement over the 1 7/8" factory headpipes that had a pretty severe crimp on both the drivers side and pass. side which reduced this inside diameter quite a big more.

I am not sure if the NBS trucks Thorleys are still a mid length design or not, I have heard they are. Anyone have any pics of the Thorleys.

I chose a standard 4 into 1 header overthe Thorleys simply because I wanted the flexability of using my own custom headpipes. I wanted the 4 into 1's LONG primary tubes for maximum exhaust tuning. The Thorleys are a long shorty with a plus size collector, the Hookers ahve 29" primaries which is what I wanted.
thorleys are an excellent tri-Y, Thorley is the only header manufacturer that is building Tri-Y's that I am aware of. TOG, The Other Guys headers also make an excellent mid length header, but are exppensive $700 plus.

If I personally owned a NBS V8 truck that was NA, I would buy a set of 4 into 1 headers with 1 5/8" primaries and 2 1/2 collectors, dual 2.5" headpipes into dual 2 1/2" cats into a single 3.5" muffler, another 3.5" pipe dumping before the pass. side tire, to keep the exhaust as short as possible, less tubing equals less friction between the tubing and exhaust pulses. Always remebering that 1 90 degree bend is like adding 3 feet of tubing to the length of the system in terms of restriction.

FI would be a 1 3/4" primary 3" collector dual 3" headpipes dual 3" cats dual 3" mufflers y'ed into a single 4 or 5" tailpipe.

Peace
Hog