1989 Fifth Avenue Dual Exhaust setup.

[Jad]

The project in mind is a dual exhaust back to the bumper on my 1989 Chrysler Fifth Avenue with the H.O 318, no cats nothing emissions related on the exhaust from factory since it's an export model. Issues is that I just read about the vented fuel tanks pain in the later models but I'm still not sure about that, and just want to make sure if the setup clears the rear sway bar. What does the conversion require to be done? (My list contains extending the fuel filler neck and moving the tank a strap to the right)

 

[Mikes5thAve]

No problem with the sway bar. I'm not sure why the thing with the vented gas tank suddenly started coming up. Moving the tank over was the way everyone did it at Farley's and it was never a big issue.

 

[Duke5A]

Wow, I thought it was cool when we got members from as far out as Europe, but I don't think we've ever had someone from the Middle East. Your car looks mint. Welcome.

I don't know when exactly, but sometime after the early 80's Chrysler switched to a gas tank with the vent in the top. It sticks upwards and sits in a pocket in the trunk floor. You can't move the tank over without it sitting incorrectly because of this.

What people would typically do is make the recess in the trunk floor bigger using a big ass hammer. It works, but it isn't pretty. After that you make the fuel filler neck longer by cutting it in half and sleeving it with fuel filler hose. Make sure you mark the original depth of the filler neck in the tank. If it isn't set right you'll have issues filling the tank.

As Mike said, your rear sway bar won't be an issue. I've got 2.5" tailpipes and it clears just fine.

Cleaner options would be attempting to find one of the early gas tanks with a flat top and using a vented filler cap. Or just having a new gas tank made (pricey).

I don't know what you have for an exhaust shop over there, but for duals it would be easiest to scrap the entire system and go new from the manifolds all the way back. 2.25" pipe is all you need.

First two photos below are with the tank being moved over a strap, and the last is a custom tank I had made when I converted to EFI.

 

[Jad]

No problem with the sway bar. I'm not sure why the thing with the vented gas tank suddenly started coming up. Moving the tank over was the way everyone did it at Farley's and it was never a big issue.

Yea I never knew it was a concern until today, I don't even know which tank i have on mine

 

[Jad]

Wow, I thought it was cool when we got members from as far out as Europe, but I don't think we've ever had someone from the Middle East. Your car looks mint. Welcome.

I don't know when exactly, but sometime after the early 80's Chrysler switched to a gas tank with the vent in the top. It sticks upwards and sits in a pocket in the trunk floor. You can't move the tank over without it sitting incorrectly because of this.

What people would typically do is make the recess in the trunk floor bigger using a big ass hammer. It works, but it isn't pretty. After that you make the fuel filler neck longer by cutting it in half and sleeving it with fuel filler hose. Make sure you mark the original depth of the filler neck in the tank. If it isn't set right you'll have issues filling the tank.

As Mike said, your rear sway bar won't be an issue. I've got 2.5" tailpipes and it clears just fine.

Cleaner options would be attempting to find one of the early gas tanks with a flat top and using a vented filler cap. Or just having a new gas tank made (pricey).

I don't know what you have for an exhaust shop over there, but for duals it would be easiest to scrap the entire system and go new from the manifolds all the way back. 2.25" pipe is all you need.

First two photos below are with the tank being moved over a strap, and the last is a custom tank I had made when I converted to EFI.

View attachment 57805
View attachment 57806

View attachment 57807

Wow Looks amazing! Thats the look I'm hunting for but maybe with smaller tips, I'm not sure if I'll be doing the manifolds i was just thinking cutting down the Y pipe and back replacing with duals and dual mufflers to keep it sinced with the classy look. Did you face the vented tank issue with your fifth avenue or is it a problem only on volares and such?

 

[Duke5A]

Wow Looks amazing! Thats the look I'm hunting for but maybe with smaller tips, I'm not sure if I'll be doing the manifolds i was just thinking cutting down the Y pipe and back replacing with duals and dual mufflers to keep it sinced with the classy look. Did you face the vented tank issue with your fifth avenue or is it a problem only on volares and such?

Yeah, I did. I was one of those that clearanced the trunk floor with a hammer. It worked, but it never sat right with me and every time I opened the trunk I could see my handy work there on the floor. You could try removing the gas tank and heating the area with a torch to attempt to make it easier to form. As far as I know every F/J/M car after a certain year used this setup.

Reason I recommend coming off of the manifolds is there isn't anything to be gained by cutting up the factory y-pipe. It merges into a single 2" pipe right off of the motor. 2.25" off the manifolds, balance pipe under the tailshaft of the transmission and mufflers under the rear seat is how I would do it.

 

[Jad]

Yeah, I did. I was one of those that clearanced the trunk floor with a hammer. It worked, but it never sat right with me and every time I opened the trunk I could see my handy work there on the floor. You could try removing the gas tank and heating the area with a torch to attempt to make it easier to form. As far as I know every F/J/M car after a certain year used this setup.

Reason I recommend coming off of the manifolds is there isn't anything to be gained by cutting up the factory y-pipe. It merges into a single 2" pipe right off of the motor. 2.25" off the manifolds, balance pipe under the tailshaft of the transmission and mufflers under the rear seat is how I would do it.

Oh yea thanks for pointing it out! Really appreciate all the info and I'll be posting how it turns out.

 

[Mikes5thAve]

The car I have with dual exhaust was done before I got it. The trunk floor wasn't messed with, I don't know what the top of the tank looks like.

 

[M_Body_Coupe]

Are you dead set on having a factory-like setup? (that being the tailpipes coming out under the bumper)

If not 100% sure, consider the alternative, that being: dump the pipes out right behind the rear wheels. You can enjoy the "engine music" a lot more (right behind your ears with the windows rolled down), also you do not have to deal with the tank re-positioning situation.

Here is the setup on my Coupe, I used to have this posted on Dippy.org forum but I think that stuff has completely been obliterated by now (sad).

 

[Jad]

Are you dead set on having a factory-like setup? (that being the tailpipes coming out under the bumper)

If not 100% sure, consider the alternative, that being: dump the pipes out right behind the rear wheels. You can enjoy the "engine music" a lot more (right behind your ears with the windows rolled down), also you do not have to deal with the tank re-positioning situation.

Here is the setup on my Coupe, I used to have this posted on Dippy.org forum but I think that stuff has completely been obliterated by now (sad).

View attachment 57808

View attachment 57809

View attachment 57810

View attachment 57811

View attachment 57812

View attachment 57813

View attachment 57814

View attachment 57815

View attachment 57816

View attachment 57817

Oh wow you kinda changed my point of view a bit, i still find it weird that they run over the leafs, might be a dumb question but do they rub or touch on hard bumps or rough roads?

 

[M_Body_Coupe]

Oh wow you kinda changed my point of view a bit, i still find it weird that they run over the leafs, might be a dumb question but do they rub or touch on hard bumps or rough roads?

LOL...yeah, I get the "weird" part of it...but it works for me.

To answer your question: NOPE, absolutely no rubbing, no touching, none of that stuff. Consider that I am also running 5-leaf spring packs and the massive MP 1" rear sway bar.

But I will say this: that's a 3" diameter pipe, and the exhaust was a custom job at a reputable shop where you can tell they knew their stuff. Welds are impeccable, etc... Bobby (the guy who still owns the shop) took the time to do this right...he is an old Mopar guy and really proud of his work.

Here (and I promise to stop before you all call me a show-off) is a shameless plug that that will give you a better feel for what the finished product looks like. Pause the video when I am at the back end of the car and you can tell how the pipes run out.