Looking for exhaust suggestions ('72 shortbed, LS1 swap)

[brossow]

For the most part I've accomplished VERY little on my project this year. Terribly, terribly disappointing, to say the least. Before I pack it up for the winter, I'm hoping I've still got a few days of sunshine here and there and with the body in the paint shop I think it would be an excellent opportunity to finish up the exhaust.

I've got an LS1 with Thorley headers. I've got a custom aluminum fuel cell under the bed out back and I'm not sure at all about the feasibility of routing the exhaust out the back. Here's what it looks like from the rear:



Instead I'm thinking about an angled dump in front of the rear tires. Here's an older shot from above:



And one from when I had the new bed on and the fender mocked up just for a general look-and-feel:



I was thinking about dumping somewhere under or immediately behind the steps. Going this route means I wouldn't have to negotiate bends over the axle, around the fuel cell, etc. Here's a shot from a low angle of the general area where I imagine the exhaust dumping:



Here are the headers hung loosely in place:




So now that everyone has seen what I'm working with, my questions are these:

1. Any problems with a relatively short, side-exiting exhaust?
   
2. I'm assuming a 3" exhaust would be appropriate. Right?
   
3. This will be a street truck only -- no serious racing of any sort. Just forget about an X-pipe?
   
4. There aren't any shops within 60 miles or more that do custom mandrel-bent exhausts, only the crappy crimped bends. I definitely don't want that, not after all the work I've put in on this project to do things right. Is there a good package available somewhere that could be adapted to meet my needs? That is, would the exhaust kits designed for '67-72 trucks with headers be more or less a bolt-on regardless of the LS1 swap? Or should I just start measuring and ordering pieces to weld together?
   
   I want to go with stainless if at all possible because in my climate stuff starts to rust just sitting inside, let alone driving. This won't be a winter truck by any means, but I don't want to see surface rust starting during the 4-6 months it's off the road each winter.
   
5. Where would you recommend I locate the mufflers? I assume as far back as possible, but obviously I'm no expert.
   
6. Anything else I'm missing?

Hope these aren't all stupid questions. I've made a lot of calls locally to try to find someone who can handle the task, but there's no one interested and capable. If I'm going to get this done this year, I need to get going ASAP.

Thanks in advance. ANY advice is greatly appreciated!

Brent

[mikajo39]

Good job on the build so far! A 3 inch exhaust would be alright and so would a 2 1/2 but a 3 inch has a good deep tone to it. Going stainless will be expensive but it's nice in the long run. A short exhaust isn't bad but you can't place the mufflers as far back as you could if it exited out the rear, My mufflers are under my bed and don't drone at all. But, I bet if they we're under the cab or close to it it'd be a lot worse. A X or Hpipe won't hurt anything, free up a few ponies and clean up the exhaust sound (less backwrap), so a x or H pipe wouldn't be bad. LMC's exhaust kit would probably be fine to modify (don't quote me on that though) How different is the header location on a LS engine swap? If you have a buddy with headers on a SBC in a truck like that just take some measurements and compare the differences.

[brossow]

Now that I look at it, going over the axle and dumping behind the rear wheels would be feasible and would put the mufflers much further back where there's a lot of open space to work with.

I'm now looking at three Pypes systems at Summit. Chambered vs. turbo -- what's the best choice?

* http://www.summitracing.com/parts/PYE-SGT79V/ (Pypes Violator - $326)

* http://www.summitracing.com/parts/PYE-SGT79R/ (Pypes Race Pro - $396)

* http://www.summitracing.com/parts/PYE-SGT79S/ (Pypes Street Pro - $396)

The first two include turbo mufflers; the third is chambered. After listening to literally dozens of vehicles with all three systems on YouTube, they all kinda sound the same to me. All three systems appear to be the same except for the mufflers. The latter two cost $79 more ($9 of which is an oversize charge; not sure why the first doesn't have it listed as well).

Again, I want to get something ordered ASAP and hopefully get the exhaust installed before the snow flies and the truck is packed away for the winter. Any input is more than welcomed.

Thanks,
Brent

[mikajo39]

Chambered Mufflers, use diffraction and bounce the exhaust sound wave around inside the muffler to cancel out the sound, flowmasters are one example of chambered mufflers. Turbo mufflers I don't know to much on what they are but I'm pretty sure they're restriction based, using stuffing and things like that. Chambered mufflers will last a long time unless they're not stainless steel and just aluminized steel because they'll eventually rust out. Even then you should still get quite a few years out of them. I'd probably go with the last choice, with the chambered mufflers. All of them look to be pretty nice though.

[brossow]

In doing a little more reading on the Pypes website, it looks like the 2.5" Street Pro chambered mufflers flow more than 100 CFM less than the Race Pro for the same price. The Violators flow the same as Race Pro, but are rated much louder, which isn't something I'm particularly interested in. (The guy I talked to at Summit tonight described the Violators like this: "You'll get a ticket for sure." Pypes rates them a 9 or 10 out of 10 on their loudness scale whereas the other two are a 7/10. Even for $80 less, no thanks!)

Will probably end up going with a Pypes Race Pro system by the end of the week. Gotta get off my butt and do something before winter is here to stay. Too bad I didn't start thinking about this a couple days earlier or I could have had something here for the weekend.

[mikajo39]

Seems like a good choice, and what kind of specs do you have on your engine, if its mainly stock you don't need a super high flowing exhaust, but if it's a souped up,cammed out, high flow heads monster than you'd need the super exhaust. Then again having an exhaust that is more than sufficient never hurt anyone

[brossow]

Engine is stock except the headers and (obviously) air intake right now, but I have a very aggressive cam I originally purchased for my '02 Z28 that may get installed before this thing eventually hits the road. Right now my goal is to get it reassembled and moving under its own power again. Iron out the bugs with the computer-controlled stuff, then start messing with the cam and valvetrain later once I know I've got it set up right in stock form. I like to have options.

[unclewatts]

It should be mentioned that bigger pipes is not always the best. Some midrange performance will be lost if the pipes are too big. I don't know what your engine likes the best, but for my 350 2.25 to 2.5" seems to work the best. My pipes exit out in front of the rear tires like you were talking about and the setup seems to work fine. A word of warning though: I'm running 2.50 pipes, Flowmaster Series 40 Classic mufflers and Hedman Headers on my 350. It's very rumbly at idle but when you jump on it, it's LOUD! If you go with 3" pipes it will be louder still. I have a friend with a newer Chev truck with a 350 and 3" pipes. That thing is unbearable. You can't even talk while your riding in it and he has the same mufflers that I do.

[Hart_Rod]

I would use 2 1/2" pipe and run them all the way to the rear. A good exhaust man will have no problem doing this. Take a look at my 68 S/C truck thread. It's lowered 6" in the rear with trailing arms, super track bar, rear mount fuel tank, external fuel pump and filter... and my exhaust man was able to take them to the rear. As far as mufflers, if you go with flowmasters, I would recommend going with the 50 series 3 chamber. It will give you plenty of rumble, but not give you headaches on long runs. I'm not sure what to recommend on the magnaflows, I have never owned a set....

[brossow]

Yeah, but as I said I can't find a good exhaust man around here who's interested in doing this. I don't care for the look of rear-exit exhaust on trucks anyway (no offense -- just see way too many tailpipes around here) and I'm really liking the Pypes systems, which I think for my tastes and needs will offer the best of both worlds. Better routing and longer exhaust, but still a side dump.

EDIT: I have to say, your rear-exit setup is extremely tasteful. I was thinking of the straight-out-the-back setups with the 4-5" tips that I see hanging crookedly on 97% of the late-model trucks around here. The angled-down look is exactly what I'm after, but out the sides rather than the rear.

[chevellelover]

i have sanderson block hugger headers and i ran 2 1/2 all the way with a x pipe right behind the tranny (4 speed truck). i cut my crossmember and ran the pipe thru it. i mounted my 44 series flowmasters a close as i could to the crossmember with 3 inch 45 degree turndowns. Its really short and loud, it may not be your taste but its a option. Before i put the turndowns i had a 90 degree pipe to the side before the tire and it looked great but didnt give the tone i wanted.

[brossow]

"Loud" is something I definitely want to avoid except under hard acceleration. Maybe I'm just getting old but I've driven enough loud, droning cars to last a lifetime.

I'm on hold right now with Summit about doing some price-matching and drop-shipping.

EDIT: Just placed my order with Summit. Got them down to $379 + s/h for the Race Pro system. Hope I don't have to do too much monkeying around with it to get it to fit!

[POPO1984]

awesome man let us know how it goes. Dont forget the pics.

[brossow]

Will do! I don't think I've ever forgotten pics — I usually go overboard the other direction.

[s_nova69]

I agree that you should stay w 2 1/2 pipes especially w exiting near or infront of the axle. I built a 3" stainless system for my 78 k20 a couple years ago w flw 50 series trying to keep it mellow unless in pedal down form. It is some what loud and this is in part to the fact that stainless exhaust resonates much more than aluminized steel and is at least %30 louder w the same si ze. I put together everything w a tig welder and mandrel bends bought and it was fun and hard. In doing this I had to change the tail pipes to 2 1/2 cut down on loud noise. This truck has a 500 hp 406" w some 1 5/8 primary headers. I am currently building a 72 shtwide Super and have the chassis done and will be putting exhaust on it in the spring and will do a version of Hart_rods rear quarter exit w the mufflers infront of the axle as far back as they can go. I have had many mufflers and have realized to always go w a bit quiter than you think they are to not be disappointed if you dont want a "loudest on the street truck". Just my two cents

[67ss&99ss]

2.5" exhaust, with an x-pipe. one chamber flowmaster racemufflers dumped. 2.5" is plenty for a stock LS1. You don't really need 3" until you put a set of heads on it and a cam in it.
My car, a 1999 LS1 Camaro SS LS1 Automatic. It has longtube headers, 2.5" exhaust, x-pipe and one chambers dumped at the rear axle.

View Video on FQuick

In this video it has tail pipes ran out the back. The tail-pipes quiet it down in the car alot but they take away from the sound inside the car. Outside the car they sound great as I rev it up.

View Video on FQuick

[brossow]

Originally Posted by 67ss&99ss

2.5" exhaust, with an x-pipe. one chamber flowmaster racemufflers dumped. 2.5" is plenty for a stock LS1. You don't really need 3" until you put a set of heads on it and a cam in it.
My car, a 1999 LS1 Camaro SS LS1 Automatic. It has longtube headers, 2.5" exhaust, x-pipe and one chambers dumped at the rear axle.

In this video it has tail pipes ran out the back. The tail-pipes quiet it down in the car alot but they take away from the sound inside the car. Outside the car they sound great as I rev it up.

Thanks for the videos -- that does sound like a great setup! I think I'll be happy enough with the Pypes setup I decided to go with. If I ever get around to installing the TSP MagicStick 3 cam and doing something with the heads, I may find the exhaust is the bottleneck in the system. Maybe I should just put it in my '02 Z28 instead. I've already got a 3" Magnaflow catback installed (along with various other bolt-ons) plus a pair of stainless Hooker LTs and a TSP ORY waiting in the wings for "someday."

[watahyahknow]

i would look around on the frame off builds on the forum here
the exaust systems shouldnt differ too mush from engine to engine and there quite a lot of people here that used blazer tanks in the rear and run exausts around them .

you do need someone willing to install the system and doing a good job ...... buying it at the place that has it mounted might get more leverage than ariving with a pile of parts and they only make money on the labour
youre install as a custom job prolly take three times as long as a regulair install and if the garage is buzy they rather make a little more by selling the bread and butter install on three regulair cars with there parts wish has a bigger profit margin.