Dual Exhaust

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87GP

Greasemonkey
Jul 15, 2006
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Looking to put dual exhaust on my 78 el camino. It had a 305 4v which was swapped out and replaced with a goodwrench 350 4v.

Looks like the left side exhaust pipe will have to sit much lower than the right side due to the configuration of the transmission crossmember. I would rather the pipe didn't sit so low. What have you guys done? Do they make a dual exhaust crossmember? Should I cut a section from the crossmember and reinforce it to get some clearance? The floor pan is also lower on the left side so the left pipe will always be a little lower. Looking at rujnning duals from the original manifolds rather than adding headers. Or should I just go with headers? Another thing is being the car is over the 25 yr old cutoff for emissions testing, I'd like to loose the cat. Muffler shops tell me they can't do that.

The local Midas Shop suggested using the original single exhaust with a dual outlet camaro muffler to give the appearance of duals at the back of the car. I thought that was kinda dumb. I want duals for the flow, not for the look. (OK maybe a little for the look LOL! )

So what do you guys think?
 

mrapii

Greasemonkey
Jan 5, 2006
198
0
0
Waipahu, HI
You need to modify the crossmember:

2286149_3_full.jpg
 

betsy84

Greasemonkey
Nov 27, 2005
140
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Toronto, Ontario, Canada
Here's what I did to my 305 Cutlass. Manifolds back, 2.25", Magnaflow muffs. All aluminized. You should go with 2.5" for the 350. You dont need anything bigger IMO.
DSC00653.jpg

DSC00654.jpg


and here's a really bad, dark, quick, 30 mins fresh on the mufflers video. Now they're more mellow, and smooth. Just for an idea of how it sounds.
 

87GP

Greasemonkey
Jul 15, 2006
178
0
0
Thanks guys!

I saw the double hump crossmembers at dixie mc and another el camino parts supplier.

I think it would be easier to just cut and weld like the pics above. Unless I'm missing something, why spend $200-$300 for a new crossmember? Is there any reason why new would be better?
 

mrapii

Greasemonkey
Jan 5, 2006
198
0
0
Waipahu, HI
The "modify existing or buy new fabricated crossmember" question has been debated many times before in other forums. I am an advocate of modifying the existing crossmember. It has been said that a heavy fabricated crossmember is stronger, it might be but my modified crossmember has survived many many hard launches (350SBC w/ 140hp nitrous shot) with no problems so I know it is strong enough. Many say that a fabricated crossmember looks better, no argument here but how often are you or anyone else gonna lie on their back and stare at the crossmember. Someone has said that the crossmember "tightens" up the frame, there might be something there but no one has ever been able to prove it. Modify the existing crossmember because it's cheaper and lighter, two really good reasons for me.
 

RedHotRegal

Master Mechanic
Mar 26, 2006
266
0
0
Ontario, Canada
I used 41/2 or 5" channel. cut from the top down so the channel sits flush with the bottom. weld it up then cut out the part for the hump. this leaves 1/8" gap between floorpan and 21/2" pipe goes straight through with no bends.
 

pontiacgp

blank
Mar 31, 2006
29,270
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Kitchener, Ontario
betsy84 said:
Here's what I did to my 305 Cutlass. Manifolds back, 2.25", Magnaflow muffs. All aluminized. You should go with 2.5" for the 350. You dont need anything bigger IMO.

betsy84 ....thats a nice job you did on your duels but do you have any cats installed...if not they can give you a serious fine for altering the emission controls on your vehicle. I got stopped once and was warned about my breather from the valve cover to the air filter was not attached. It's not the cops who stop you but the evironment enforcement...
 

RedHotRegal

Master Mechanic
Mar 26, 2006
266
0
0
Ontario, Canada
Here in Ont. the police can send you to the MTO. You are given 24h to show. I used 2 old cats, gutted them, then ran tubing straight through before I finished welding them up I filled them with sand. They are on my buddies SS. He's been stopped before, and said they tapped them to see if they were hollow. But what they dont know wont hurt them :lol:
 

pontiacgp

blank
Mar 31, 2006
29,270
20,391
113
Kitchener, Ontario
red.... your right about the cops could send you to the MTO but the environmental enforcement guys can ticket you on the spot and can have the vehicle towed and impounded.... :evil:
 
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