Right now i have a flowmaster american thunder 3" mandrel bent system in my ta.is that big enough for when i drop the 406 in?..from what ive read i should have around 420-440 at the wheels...or should i step up to a 4" mufflex system .
($1,000.00 for cat-back/y pipe)

True dual 3" is fine, if that is what you are talking about.

------------------
70 SS 454 CI Dynoed 684 HP, 702 TQ All Aluminium Fuel Injected Small Block , plus 200 - 500 HP NX nitrous system.

[This message has been edited by Rick WI (edited January 03, 2005).]

Dual 3" exhaust will support 600Horsepower no problem

How much is it that a 2.5" dual system will support?

No.. 95 % of the 82-92 firebird exhaust systems are are a y pipe that go into a single pipe that goes into a crossflow muffler that spits out rear "duals"..not a real dual system though.

as for as duals go..its a very hard conversion from what ive heard..and expensive.

If you are talking about an '82-92 system that has a 3" single pipe, the general concensus (sp?) over at thirdgen.org is that its good to about 400-450hp.

real true duals on a third gen aint that hard to do now. Had mine for about 7 years on 2 cars, back then it was a pain, cause only 2 brands of headers was out, and bought was shortys, now it's diff.

There's been quite a few post on www.thirdgen.org (http://www.thirdgen.org) about it. The last one I can remember is "duals aint gonna work" Alot of good info and pics in that thread on how to do it.

If your starting with a new combo the cheapest easy way is below. We're doing the same with my dad's 82 327 firebird

hedman long tube headers $136
hedman S pipes $22
Summit X pipe $80-90 (based on size)
Summit turbo mufflers $30 for both
Summit 2 4' long tail pipes $25 (if you want to go stright out the back, or you could just put turn downs on the mufflers)
6 hangers $24

Total of $317.

Can be welded up at home with a cheap welder, no bending, no custom work, or if no welder, clamp it all up and go to an exhaust shop to have it welded. Shouldnt be no more than $5 a weld at most(10 welds).

(driver side header will need alittle tweeking, and a-arm mounts has to be ground on driver's side read on thirdgen.org)

As far as pipe size, I run true dual 2.25" on my 88 camaro. E/t-ing in the high 12's, trapping at 118 mph (power to go mid 11's with traction)

The info I have says about like what Air_Adam said 400-450 max at the crank (328-369 rear wheel HP) max for a 3" single manderl bent

Look how much power the LS1/LS6 puts out with a 3 inch single pipe split to fake duals! I'm running headers that join into 3 inch tubing, through the cat, and then splits back to dual 2-1/2 inch pipes. I'm running a 400 sbc and it doesn't seem to be holding it back much.

<font face="Arial,Verdana" size="2">Originally posted by 1978LT:
Look how much power the LS1/LS6 puts out with a 3 inch single pipe split to fake duals! .</font>

-I dont know..are talking about stock..how much?

-if a 3" system can support 450hp at the crank im sure that 4" will support 500hp.
I'll prolly just go with this.It says it supports 400 at the wheels..but i think it would go for more.

http://www.mufflex-performance.com/fbody_2.html

item#82401C-DT

I've done quite a few 3rd gens with big cube small blocks (street stuff) and a single 3" exhaust doesn't seem to be much of a problem at that power level, in my experience.

Had a 408 with a MiniRam on top that laid 410 out the back and that was through small tube shorty headers into a y-pipe with 2-1/2" down-tubes and a complete 3" exhaust WITH 3" HIGH FLOW CAT and an SLP 3" muffler with "2 on da lef" tailpipes that were each 2-1/2" diameter.