Dual pipes with X pipe muffler

[CalebAdams]

Hey guys, new to the forum. I have recently bought my great grandpa’s ’90 K1500 that has the TBI 350 and I’m want to slowly build it into an overlander. I had some questions about a new exhaust I was thinking of having made for it. Right now it has the stock 2.25” down pipes that Y into a 3”, and goes into the stock cat. From there my great grandpa had a new muffler installer a long time ago. It splits the 3” back into 2 2.25” pipe, and they both come out the passenger side behind the tire. I was thinking about replacing it all from the manifolds back with a 2.5” true dual exhaust, with a Magnaflow 2.5” dual in/ dual out 4” x 9” x 14” oval that has an integrated x pipe (Magnaflow lists it as #11386). My questions are if the 2.5” pipe would be too big for my stock 350, if just the x pipe muffler would be enough for proper scavenging, and if the muffler would be too loud. I don’t want it to be excessively loud, just a nice low rumble to it. I’d like to have the ends come out where it does right now. I’ll attach a pic of a sketch if I can, plus one of my truck. Thanks

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[Erik the Awful]

Here's my 2.5" with long tube headers and cats. It's loud and boomy, but I plan on extending the tailpipes out over the axle in the next couple weeks. I used Cherry Bomb Salute mufflers, a Jones x-pipe, Flowmaster(?) cats, and Summit headers.
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[Pinger]

How important is the X-pipe and what does it do?
My dual system doesn't have one - each cylinder bank is completely independent of the other - should it be that way? Am I losing out on anything? (That's on a 350 Vortec BTW).

 

[CalebAdams]

Here's my 2.5" with long tube headers and cats. It's loud and boomy, but I plan on extending the tailpipes out over the axle in the next couple weeks. I used Cherry Bomb Salute mufflers, a Jones x-pipe, Flowmaster(?) cats, and Summit headers.
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Cool. I figured, if anything, all I’d do is short tube headers. Hopefully the Magnaflow will be around how loud I want it to be

 

[b454rat]

X or H pipe will get rid of drone. X pipe is for higher RPMs, H for low end. X pipe has a different sound to it, I had one with a healthy 468 and had a snow mobile whine or sound to it, but it sounded good!!! Either one helps scavenge exhaust.

 

[b454rat]

Erik, is ur exhaust just some straight pipes n some bends? Looks pretty simple but pretty slick.

 

[PlayingWithTBI]

Check out this exhaust system. I took these pics back in 08 when my son and I went to the races in Phoenix. This is a mock-up of a truck on a rotisserie when it was the Craftsman series. Note the Tri-Y headers and giant H pipe.

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How about this for a suspension?

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[Erik the Awful]

Erik, is ur exhaust just some straight pipes n some bends? Looks pretty simple but pretty slick.

Yup, thanks! I did have to build a lowered transmission crossmember to clear the cats. I have a parts list on one of these pages, but it's not on my build thread. I believe I bought it all from Summit for under $300, including headers. I welded it myself, and for the first time my welds didn't look like bird crap. The new tubing I got to extend it over the rear axle was another $65.

How important is the X-pipe and what does it do?

The exhaust pulses in each pipe are not constant. If you think about the firing order 1-8-3-4-6-5-7-2, it goes into the pipes as L-R-L-R-R-L-L-R. Your exhaust pressure is not only pulsing, but the pulses fluctuate in size. What if you could use the velocity of big pulses in one pipe to help speed up the gases in the other pipe, and reciprocate? That's what a "crossover" does. It makes a very noticeable difference on the dyno. b454rat has it right, H pipes for torque, X pipes for horsepower, but either will beat no crossover. My pre-fabbed X-pipe I used cost less than $20. That's as close to free horsepower as you get.

 

[b454rat]

Once garage is up, think might copy ur set up lol

 

[L31MaxExpress]

Tri-Y headers into a Merge Y or X-pipe have worked best for me for torque.

FWIW my 1997 Express van 350 Vortec was dual 3" to the muffler from GM.

I have a 3.5L V6 with equal length, merge collector shorty headers, dual 2.5" pipes and a X after the high flow cats. It smokes the tires anywhere in 1st gear.