Routing of exhaust - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rrenner · 02-08-2015, 02:46 PM

Starting to plan the layout of exhaust. I'm looking for advise on routing. I am running a 350 with 3" rams horn manifolds. I was considering a cross over pipe and running out just under steps on bedsides. Maybe too short a distance for cross over and mufflers? Passenger side has break booster to deal with. Over or under cross members? Cross over a pain with trans and drive shaft in the mix? Any thoughts or pix will be appreciated..

Bad Apache · 02-08-2015, 03:45 PM

Are you running 3" pipe the whole way? You can support over 1000whp through dual 3". So it may be over kill. But it does sound good! I'd suggest dual 2.5", a crossover/h-pipe behind the trans (for space) into a pair of mufflers that you like and pipes out the back. You may be able to package it all before the steps and do 90* elbows and out where you want it depending on muffler length. As far as cross members go, it'll depend on what size pipe and space you have available. I like it tucked up as tight as possible. Looks cleaner and reduces the chance of dragging it on something if your truck sits low.

OrrieG · 02-08-2015, 04:29 PM

Where did you get 3" rams horns, biggest I have seen are 2.5" which are still reproduced for the stock racing classes? I have 2" rams horns that transition to 2.5" pipe. First go around I ran 14" mufflers and dumped them right behind the cab. The reverberations at idle and slow speeds drove me crazy. Bonus was at just off idle it would set off car alarms in parking garages! This time I moved the muffler back and got the longest I could get, 28" I think and will dump them either out the passenger side in front of the wheel opening or dump them just in front of the axle.

rrenner · 02-08-2015, 04:55 PM

Oops, 2.5" my bad. thought stock was 2.5 was the stock manifolds and 3" was the more open ones.... My thought for not running them to the back was clearance around a mustang fuel tank and saving some of cost of material, (minimal). The alarm thing sounds fun though..

_Ogre · 02-09-2015, 02:21 PM

you have to remember that the frame on these trucks is above the body sheet metal
i ran my exhaust under the frame which also put it under my hydroboost

and i agree with orrieg; if you don't exit out the back you will have more exhaust noise and possible drone
with a flipped axle space is tight but i believe with heat shields over the pipes i can get over the rear axle

octanejunkie · 02-09-2015, 02:59 PM

I ran my 2.5" dual exhaust from the rams horns all the way back about 5-6" inboard from the frame rails, exiting behind the rear wheels.

I went back after the fact and added an H pipe crossover over the trans tailshaft, just behind the crossmember. It made a big difference in sound and was a mild performance benefit.

roger55 · 02-09-2015, 07:21 PM

rrenner · 02-09-2015, 10:49 PM

Thanks to all, Roger55 great pictures, checked out your build thread, beautiful truck. May I emulate? thanks again..

roger55 · 02-10-2015, 12:07 AM

Quote:

Originally Posted by rrenner

Thanks to all, Roger55 great pictures, checked out your build thread, beautiful truck. May I emulate? thanks again..

You are welcome.
Plagiarize to your heart's content!

**mr48chev** · 02-10-2015, 11:37 AM

From past experience of driving four trucks with loud exhaust dumping in front of the rear wheels I'd suggest mufflers that muffle a bit more if you do dump the exhaust in front of the rear wheels.

That noise is fun around town but on long freeway road trips the constant drone gets pretty tiresome.

Goldengophersax56 · 02-13-2015, 03:59 PM

He mentioned clearance under a mustang fuel tank going out the back. Will that still be an issue? I am thinking about doing the same thing if I can.

octanejunkie · 02-13-2015, 06:53 PM

Quote:

Originally Posted by Goldengophersax56

He mentioned clearance under a mustang fuel tank going out the back. Will that still be an issue? I am thinking about doing the same thing if I can.

This makes dropping the fuel tank a real PITA... just sayin'

_Ogre · 02-13-2015, 08:12 PM

as your exhaust comes over the rear axle, swing it out under the frame and run straight back

Speedbumpauto · 02-14-2015, 11:36 AM

Something to consider when routing to the rear is splitting the "tailpipe" at the hump. My exhaust is a little more complicated than some cuz I had to have the big boy toy cutouts, but I was able to solve the over the axle and clear the tank problem by splitting the tailpipe using 2 1/2 collector flanges. When I fabbed up the pipe to do what it needed to do on a lowered truck with a four link, it was impossible to snake a complete tailpipe over the axle to the muffler. Might be a little out of the box but the flanges made a hard problem easy.

02-08-2015, 02:46 PM	#1
rrenner Registered User Join Date: Mar 2014 Location: Chickamauga Posts: 69	Routing of exhaust Starting to plan the layout of exhaust. I'm looking for advise on routing. I am running a 350 with 3" rams horn manifolds. I was considering a cross over pipe and running out just under steps on bedsides. Maybe too short a distance for cross over and mufflers? Passenger side has break booster to deal with. Over or under cross members? Cross over a pain with trans and drive shaft in the mix? Any thoughts or pix will be appreciated.. __________________ 1958 Apache short bed

02-08-2015, 03:45 PM	#2
Bad Apache Registered User Join Date: Feb 2015 Location: Mechanicsburg, PA Posts: 93	Re: Routing of exhaust Are you running 3" pipe the whole way? You can support over 1000whp through dual 3". So it may be over kill. But it does sound good! I'd suggest dual 2.5", a crossover/h-pipe behind the trans (for space) into a pair of mufflers that you like and pipes out the back. You may be able to package it all before the steps and do 90* elbows and out where you want it depending on muffler length. As far as cross members go, it'll depend on what size pipe and space you have available. I like it tucked up as tight as possible. Looks cleaner and reduces the chance of dragging it on something if your truck sits low. __________________ 1958 Apache 454ci 4 speed

02-08-2015, 04:29 PM	#3
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: Routing of exhaust Where did you get 3" rams horns, biggest I have seen are 2.5" which are still reproduced for the stock racing classes? I have 2" rams horns that transition to 2.5" pipe. First go around I ran 14" mufflers and dumped them right behind the cab. The reverberations at idle and slow speeds drove me crazy. Bonus was at just off idle it would set off car alarms in parking garages! This time I moved the muffler back and got the longest I could get, 28" I think and will dump them either out the passenger side in front of the wheel opening or dump them just in front of the axle. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

02-08-2015, 04:55 PM	#4
rrenner Registered User Join Date: Mar 2014 Location: Chickamauga Posts: 69	Re: Routing of exhaust Oops, 2.5" my bad. thought stock was 2.5 was the stock manifolds and 3" was the more open ones.... My thought for not running them to the back was clearance around a mustang fuel tank and saving some of cost of material, (minimal). The alarm thing sounds fun though.. __________________ 1958 Apache short bed

02-09-2015, 02:21 PM	#5
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Routing of exhaust you have to remember that the frame on these trucks is above the body sheet metal i ran my exhaust under the frame which also put it under my hydroboost and i agree with orrieg; if you don't exit out the back you will have more exhaust noise and possible drone with a flipped axle space is tight but i believe with heat shields over the pipes i can get over the rear axle __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

02-09-2015, 02:59 PM	#6
octanejunkie Registered User Join Date: Jan 2015 Location: Santa Monica Posts: 264	Re: Routing of exhaust I ran my 2.5" dual exhaust from the rams horns all the way back about 5-6" inboard from the frame rails, exiting behind the rear wheels. I went back after the fact and added an H pipe crossover over the trans tailshaft, just behind the crossmember. It made a big difference in sound and was a mild performance benefit. __________________ Déjà vu. It's that feeling you get when you hit your thumb with the hammer a second time '59 Chevy 3100 Stepside

02-09-2015, 07:21 PM	#7
roger55 Registered User Join Date: Feb 2010 Location: San Angelo, Tx Posts: 1,068	My 3200: __________________ *'57 3200 Build Thread* *My Gas Station Themed Workshop*

02-09-2015, 10:49 PM	#8
rrenner Registered User Join Date: Mar 2014 Location: Chickamauga Posts: 69	Re: Routing of exhaust Thanks to all, Roger55 great pictures, checked out your build thread, beautiful truck. May I emulate? thanks again.. __________________ 1958 Apache short bed

02-10-2015, 11:37 AM	#10
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,711	Re: Routing of exhaust From past experience of driving four trucks with loud exhaust dumping in front of the rear wheels I'd suggest mufflers that muffle a bit more if you do dump the exhaust in front of the rear wheels. That noise is fun around town but on long freeway road trips the constant drone gets pretty tiresome. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

02-13-2015, 03:59 PM	#11
Goldengophersax56 Registered User Join Date: Jan 2015 Location: Lino Lakes, MN Posts: 60	Re: Routing of exhaust He mentioned clearance under a mustang fuel tank going out the back. Will that still be an issue? I am thinking about doing the same thing if I can.

02-13-2015, 08:12 PM	#13
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Routing of exhaust as your exhaust comes over the rear axle, swing it out under the frame and run straight back __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

02-14-2015, 11:36 AM	#14
Speedbumpauto Registered User Join Date: Aug 2011 Location: Tucson, AZ Posts: 917	Re: Routing of exhaust Something to consider when routing to the rear is splitting the "tailpipe" at the hump. My exhaust is a little more complicated than some cuz I had to have the big boy toy cutouts, but I was able to solve the over the axle and clear the tank problem by splitting the tailpipe using 2 1/2 collector flanges. When I fabbed up the pipe to do what it needed to do on a lowered truck with a four link, it was impossible to snake a complete tailpipe over the axle to the muffler. Might be a little out of the box but the flanges made a hard problem easy. Attached Images



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