454 dually header/exhaust question
 

My dually has headers that form into one tube similar to stock, this is a 3" in outlet, question is what are my options for down stream, a single 3" muffler? or do they make a kit where it splits right after the headers? currently has a single inlet and outlet flowmaster, better muffler options?

Re: 454 dually header/exhaust question
 

What year is your truck? Trying to figure out why a single exhaust vs dual exhaust.

From a different point of view, a 3" single exhaust flows about the same as a 2-1/4" dual exhaust if the intersection of the two pipes is not sharp. I have a 1979 C3500 Dually with headers and dual exhaust (it came from the factory with dual exhaust and no converter) and it is currently in need of a new system - plan on using a new set of Hedman Elite Heders along with a 2-1/2" dual system, they are available from Flowmaster and Pypes.

Re: 454 dually header/exhaust question
 

its a 91 with throttle body injection and an o2 sensor in the pipe, I picked it up this way, the headers are stainless and not looking to replace, thinking changing the down stream setup

Re: 454 dually header/exhaust question
 

A 91 with throttle body injection will see no noticeable gains by using headers. Going back to the stock manifolds, a free flowing cat convertor an using a heated O2 sensor with the single 3'' pipe will be your best bet unless there were significant changes to the internals of the engine and a new programmed chip

Re: 454 dually header/exhaust question
 

i got with the headers on, not changing them, heated o2? There is no cat...

Re: 454 dually header/exhaust question
 

If the O2 sensor is anywhere downstream you need a heated O2 sensor to operate properly (with or without a cat). If emission testing is not an issue (you mentioned no cat) I would go with one of the dual exhaust kits and get a collector that has the bung for the O2 sensor and wire in a heated O2 sensor.

The factory 454 TBI exhaust had two choke points, the factory "Y" pipe overlapped inside where the two pipes met, and the stock muffler choked down to 1-7/8" just inside of the 3" inlet. Because of excessive heat the converter was placed after the muffler. The exhaust manifolds themselves were not bad considering they had a 2-1/4" outlet. I mention this because if your system is using the original "Y" pipe cut to fit, you have the issue of the overlap at the connection of the two pipes.

Re: 454 dually header/exhaust question
 

no testing here, wisconsin, and the o2 is in the header, this is like a tri y set up that the ps comes over and meets with the ds then has a 3" outlet, I guess a y pipe of sorts, thanks for the info all yall!

Re: 454 dually header/exhaust question
 

This is how mine is done. 1.75 x 3" full length headers into dual 3" head-pipes; though an 'H" pipe; into 3" In/Out mufflers; then reduced down to 2.5" dual tailpipes that discharge @ the rear bed corners.

Re: 454 dually header/exhaust question
 

nice, carbed big block?

Re: 454 dually header/exhaust question
 

TBI. Edelbrock TBI intake w/coolant loop deleted & TBI chip for the ECU. Does ok but the idle hunts (surging @ idle). I don't drive it enough to worry about it but it does fine @ speed.

I've debated swapping to a carb or spending more & switching to a Holley EFI set-up that's NOT TBI based. Most likely it will get a carb because big-blocks in CC duallys aren't exactly efficient so it seems ROI would be nonexistent.

Re: 454 dually header/exhaust question
 

where did you put to o2? how do you like that intake? did it make a diff?

Re: 454 dually header/exhaust question
 

o2 sensor is near the end of the collector. You have to make sure there's X-amount inches of exhaust tubing post sensor (I don't recall what it was @ the moment).

My truck had the factory GM cast iron QJ carb intake w/the aluminum TBI 'adapter' so it's a better intake (looks & weight). Hard to say performance wise as the cast iron/adapted TBI set-up had 100k on the clock (dished pistons/wear & tear/stock cam etc....) vs. a fresh flat-top piston long block + BBC Melling 'RV/Towing' cam (same OE heads just rebuilt w/the block).

Truck can light up the duals post build vs when I bought it. Definitely feels more responsive but it's hard to say what the largest contributor to that is/was.