Critique my exhaust design please, 1996 RCSB 5.7 vortec with Pacesetter longtubes

[linexrandy]

I drew this up tonight after crawling around under the truck for awhile. I got the longtubes installed and they sound sick! Havn't run on the street because when you put it in drive (when I pull it out of the garage to work on it) it backfires about every 2 seconds so I know the computer is confused. Will get a tune after I'm done with the exhaust.
The plan:
-Instead of a Y-pipe I'm thinking of running true duals to the muffler. Muffler will be 2.5" dual in/out Spintech 6000. I'm putting thunderbolt cats on to act as resonators as I hate the glasspack crackle.

- Pacesetter longtubes come with the reducers which neck it down to 2.5", so I will run this size exclusively through out. I measured and the pipe from the drivers side will run under the front of the driveshaft, just under the tailshaft, with about 2" of clearance and will not hang down below the crossmember. No issues there.

I know I'm being paranoid, just hate wasting money. I think this exhaust will sound great (not really looking to be the loudest). I just want nice, clean, racey sound with minimal "glasspack crackle". Anyways, here's my scribble. Tell me what you think.
http://i249.photobucket.com/albums/gg238/linexrandy/Exhaustdesign.jpg

[Benny00Z71]

looks good to me

[95nProgress]

You should put your cats as close to the header collectors as you can, heat is what makes them work. The drivers side one is way too far down the exhaust path.

Brian

[Benny00Z71]

You should put your cats as close to the header collectors as you can, heat is what makes them work. The drivers side one is way too far down the exhaust path.

Brian

Good point. If you look at the cats on the 5.3 Y pipe they are both right after the collectors.

[Low97tahoE]

Good point. If you look at the cats on the 5.3 Y pipe they are both right after the collectors.

im sure closer to the headers is better, but if u look at the stock Y on a 5.7, both cats are on the pass side, so the one in the pipe that crosses over from the drivers side is pretty far down, just sayin

[Jagsweb]

Try this....... Install a 2" or 2-1/4" tube that connects right and left sides at a point about 6" ahead of the muffler. That will give an "H-pipe" configuration which will enable the engine to "see" a system that will appear much larger than what you're building.

[silverado_lover]

You basically have the same setup I'm running now, I have a 3" y pipe coming off the headers and I have a coupler to bring the pipes to a single pipe.

You won't have any glasspack crackle at all, it's going to be really deep cruising but when you get on it, it's really going to scream.


Disclaimer: My truck has LS awesomeness

Edit: my cats are directly connected to the headers


Sent from my dishwasher

[linexrandy]

Yeah I can put the cats right up to the reducers. Plenty of room. Gonna have to wait and save up a couple paychecks before I do this so I have time to get opinions. I'm back to leaning towards the y pipe into a single in, dual out spintech. I think it would be simpler, sound good, and no need for H pipe. So would yall run a cat on each collecter or the Y pipe into a single cat? I'm thinking 2 right at the collector.

[SUBURBIAN]

im sure closer to the headers is better, but if u look at the stock Y on a 5.7, both cats are on the pass side, so the one in the pipe that crosses over from the drivers side is pretty far down, just sayin
I believe the driver side cat is closer to the engine on my vortec 350. Further downstream is where the passenger side cat is located, to make them more equidistant from the manifolds, as this is the optimal setup.


OP, Using converters as resonators is a bit odd. I think you're better off with a muffler that gives the tone you want instead. You yourself said you dislike wasting money. 2.5" to the bumper is a waste of $. The gases are cooled and slowed enough coming out of the muffler(s) that a step or two down in pipe diameter is adequate. Also muffler(s) should be placed as far downstream as possible.

[silverado_lover]

Yeah I can put the cats right up to the reducers. Plenty of room. Gonna have to wait and save up a couple paychecks before I do this so I have time to get opinions. I'm back to leaning towards the y pipe into a single in, dual out spintech. I think it would be simpler, sound good, and no need for H pipe. So would yall run a cat on each collecter or the Y pipe into a single cat? I'm thinking 2 right at the collector.

Now that I'm off my phone I'll post some picz

http://i978.photobucket.com/albums/ae267/mrmason17/LS%20Swap/P3190754.jpg
http://i978.photobucket.com/albums/ae267/mrmason17/LS%20Swap/P3190750.jpg
http://i978.photobucket.com/albums/ae267/mrmason17/LS%20Swap/P3190751.jpg
http://i978.photobucket.com/albums/ae267/mrmason17/LS%20Swap/P3190753.jpg
http://i978.photobucket.com/albums/ae267/mrmason17/LS%20Swap/P3190756.jpg

And a rev to only 2500 RPM


http://www.youtube.com/watch?v=bGz86uHr2gA

[Chevy53]

silverado_lover how those band clamps working no leaks form headers?

[silverado_lover]

Surprisingly well

[linexrandy]

Thanks for the pics silverado_lover, pics really clarify things for simple minded folk like me. So you said you had cats off the headers but I didn't see them in pic. Also, whats your thoughts on the 3" into the muffler? 2.5" should give a little more low end I was thinking? I'm basically going to steal your design but may do 3" into the Y then 2.5 back to single in, dual out spintech. I need opinions on the benefits of using 3" vs 2.5" (hopefully from people like silverado_lover that have or have had both). Remember motor is stock, will be tuned after exhaust.

I don't mind spending $80 on a pair of highflow cats but if yours sounds that good without them I'll just leave them off.

The reason I planned on running them out the back is the truck came with some nice 2.5" flowmaster tailpipes that don't reduce down at the bends at all (don't remember what its called, Hydoformed???) so that will not cost me anything. I had turned downs on my last truck and liked them and would probably do them if I already didn't have the pipes.

[silverado_lover]

My cats are completely hidden above the trans crossmember :lol:

My cats cost a total of $68 shipped to my house, you'll definitely want 3" pipe back back to the muffler. A single 2.5" will have plenty of exhaust velocity but too much backpressure.
Sent from my dishwasher

[jaredself]

Wow, small world. I used to live in Childress.

[linexrandy]

Wow, small world. I used to live in Childress.

Haha yeah I just moved up here from Buffalo Gap, south of Abilene. Like your avatar says much of west Texas IS bfe!

10-4 on the cats silverado_lover

[jaredself]

Haha yeah I just moved up here from Buffalo Gap, south of Abilene. Like your avatar says much of west Texas IS bfe!

10-4 on the cats silverado_lover

Got that right. Find Toyahvale on a map and see where I am now, haha.

[linexrandy]

On another note, the headers I have don't have the EGR bung, so I'm deleting it. Right now the hose is just hanging there. I've got the O2 sensors plugged into the headers. I'm pretty sure it's because of a lack of backpressure and the computer trying to figure out whats going on, but the truck idles at 1000 rpm and backfires about every second or two when you put it in gear so I havn't drivin it around the block. Just wondering if plugging that hose would do anything or just need to get the exhaust finished before I take it out.

[linexrandy]

Fixed the back firing issue. Got this blockoff plate in and installed: http://www.ebay.com/itm/CHEVY-S-10-S10-SATURN-BILLET-CPI-EGR-BLOCK-OFF-VORTEC-/250943161769?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26o tn%3D5%26pmod%3D220565786482%26ps%3D63%26clkid%3D7 099959597912485143
and plugged the intake port via welding a bolt head into the nut. Still not sold on using 3" with a stock motor. I'm probably gonna go with 2.5" throughout. BTW Truck is doggy as hell with open headers and no tune. Lost tons of bottom end (as to be expected).

[silverado_lover]

I'm lost as to what your plans are now :lol:

If you do a single exhaust, 2.5" y pipe, to a 3" single pipe.

If you do troo duels (kekeke) 2.5" pipe all the way.


I have a 3" y pipe but I do plan on some more mods for the 5.3 :burn:

[SUBURBIAN]

Stockish 350 will lose seat of the pants power with 2.5" dual exhaust and good flowing mufflers.

[linexrandy]

Plan is to use the reducers I have from pacesetter that neck collectors down to 2.5". Cat off each reducer. 2.5" Y pipe. 2.5" all the way back to spintech 6000.

I just have a feeling that 3" is too much and will make it doggy on the bottom end.

[silverado_lover]

Stockish 350 will lose seat of the pants power with 2.5" dual exhaust and good flowing mufflers.

Interesting...then what size pipe?


Plan is to use the reducers I have from pacesetter that neck collectors down to 2.5". Cat off each reducer. 2.5" Y pipe. 2.5" all the way back to spintech 6000.

I just have a feeling that 3" is too much and will make it doggy on the bottom end.

I didn't even have longtubes and I had a 2.5" y pipe going to a 3" pipe, IIRC the TBI trucks had a 2.xx" y pipe going to a 2.75" pipe.

I've never heard of anyone running a 2.5" single exhaust on anything bigger than a 305 :lol:

Here's my old 0-60 for good measure...keep in mind this motor isn't as power full as yours



http://www.youtube.com/watch?v=gTPzjrHm-qA

Edit: Seeing my truck shift before the tach is pegged out is lulzy