Installing Dual Exhaust

[Jeff Roblin]

Because of the offset gas tank and little clearance with the leaf springs, many have questioned how dual exhaust would fit on their GMV.

One of our members, Bruno Fronzaglio who resides in Donora, PA has THREE GMV:

'76 Granada Sports Coupe
www.gmv-registry.com/generic572.html
'77 Granada 2dr
www.gmv-registry.com/generic133.html
'77 Monarch 2dr
www.gmv-registry.com/generic134.html

Below shows the pictures of installation of dual exhaust on a 351W GMV:

[Jeff Roblin]

Another of our members, Henrik, who resides in Denmark owns 2 GMV's

'77 Granada Ghia 2dr
www.gmv-registry.com/generic125.html
'77 1/2 Granada Sports Coupe (Spring Edition)
www.gmv-registry.com/generic375.html

Below shows the installation of dual exhaust on his 302-auto Sports Coupe:

[hipogranada]

This addresses two frequent questions about running duals on these cars - one, with converter intact and the other, eliminating the converter.

In my state, cars 25 years and older are no longer required to meet emissions standards - so ditching the cat is an option.

[jhkaster]

From the look of these two examples, one car splits the exhaust after the converter and the other splits starting at the manifolds. I'm assuming that splitting from the manifold has the best benefit in terms of horsepower gain. But is it a significant difference or small?

I'm thinking about putting a dual exhaust on my Versailles, but I would probably have to have dual catalytic converters, mufflers and resonators for both state inspection and quietness if I split from the manifolds.

[hipogranada]

James, Henrik's car now has long-tube headers so that changed the picture considerably.

As far as what you'd gain from installing true dual exhaust on your car... maybe not a lot. Freer-flowing exhaust helps, but I doubt there's that much gain without induction and cam change. Henrik's SC project includes a swap to Edelbrock four-barrel manifold and carb and a hotter camshaft. The exhaust will probably do him a lot more good than it would on a stock two-barrel 302.

That said, there's a lot to be said for the sound of a real dual-exhaust system, even with dual cats and real mufflers. If you decide to make the change, you may want to ask the muffler shop to fabricate an equalizing tube between the two sides, or in other words an H-pipe. You see that on Henrik's installation. Evens out the sound and helps power output.

jhkaster said:

From the look of these two examples, one car splits the exhaust after the converter and the other splits starting at the manifolds. I'm assuming that splitting from the manifold has the best benefit in terms of horsepower gain. But is it a significant difference or small?

I'm thinking about putting a dual exhaust on my Versailles, but I would probably have to have dual catalytic converters, mufflers and resonators for both state inspection and quietness if I split from the manifolds.

[hipogranada]

Consider this as another alternative way to run tailpipes on a dual exhaust installation. This is a photo of the factory tailpipe exit on a '70 Cyclone GT 429CJ. Torinos used this as well. It has a factory appearance and isn't showy, but gets the job done well, and it eliminates the problem of the offset gas tank on GMVs.




Here's the same setup on a '64 Falcon, which has similar OE muffler location to the GMV.



Personally, I like this setup. It has more of a sleeper/OE look than exiting under the bumper.

[maxford]

has eny body tried 66 mustang try y headers

[sixty9santa]

If Hooker's Competition 6901 full length headers will fit, in the long run I'm planing to get a pair of Flowmaster Super 44's (2.5" in/out), 3" to 2.5" reducers, Flowtech's 2.5" Universal X-pipe kit, welding up the whole shabang and turning it into a side exhaust setup.
Any thoughts?

[sixty9santa]

Hi Henrik,
Curious to know what kind of exhaust kit you used?

[hipogranada]

That wasn't a kit. I believe Henrik had that exhaust custom fabricated in stainless. He's in Denmark so his sources are sometimes not the same as ours.

Mar 11, 2008 15:07:15 GMT -5 sixty9santa said:

Hi Henrik,
Curious to know what kind of exhaust kit you used?

[baun]

Hi,

I use edelbrock mufler and I designed the exhaust myself, and had a friend make it ;D

you can hear the sound here,
s182.photobucket.com/albums/x223/baun3042/?action=view¤t=Testbnk009.flv

you can see the exhaust here,
americangranada.dk/doubleexhaust.htm

Henrik, Denmark

[Grant]

I installed a 351 windsor with Edelbrock aluminum heads and a warmed up cam along with the Edelbrock performer intake and Holley 670 carb on my '76 Granada four speed car. I used 2.5" pipe except for 2.25" around the firewall, to miss the clutch linkage. I used a 70/71 Cougar exhaust manifold on the drivers side. I then crossed the passenger side exhaust over and paralled the passenger side exhaust out the rear (European style). Sounds awesome.

[sixty9santa]

So I've almost acquired every single part for the dual exhaust, side exit before the wheels setup.
The final parts list is as follows:

-Hooker Competition 6901HKR headers
-Headman power steering drop bracket (part#: 20120)
-Pypes polished 304SS 2.5" Universal Special x-pipe kit (part#: XVF10S), the pipes go in the driveshaft tunnel
-Two Magnaflow same side 2.5" inlet/exit Polished SS muffler (part#: 14210)
-Two Magnaflow SS 45deg. J-bends (part#: 10706)
All I need to do now is weld some SS collectors, fab up some tips and hangers, and start welding.

Just another quick question since my system won't have cats, how do I bypass/remove the oxygen sensor from the cat converter?

[hipogranada]

It's so easy, it's like you don't have to do a thing. Because you don't have to do a thing. There is no O2 sensor because it isn't computer controlled.

Just another quick question since my system won't have cats, how do I bypass/remove the oxygen sensor from the cat converter?

[sixty9santa]

Sweet!