Large Diameter Exhaust on a Street Car

[ykf7b0]

I have a 69 roadrunner and I am running headers with 3 inch collectors and pipes with a crossover pipe ran through a pair of Dynomax turbo mufflers with turndowns at the rear axle. I am contemplating running the exhaust all the way out to the rear bumper and installing some 3 inch road runner stlyle tips I have spotted on ebay. I have an electric fuel pump and filter mounted onto the inside frame rail on the passenger side.
I am curious as to whether any of you performance minded Moparites are running large diameter exhuast and if any problems exist. Thanks!!!

 

[HEMI-ITIS]

You didn't indicate what performance level you are at.I have a 4 inch stainless system with "X" pipe.It's real nice not havin' fumes come into the car from turndowns at the axel!!

 

[ykf7b0]

Thanks HEMI-ITIS! My roadrunner has only been on 1/8 tracks and it is good for 6.90's We drive it hundreds of miles on our outings so the fumes are a problem. That is a great looking Beast you have there I might add!!!!

 

[Moose]

I agree... Nice for sure. I have a four link and I wonder about the exhaust problem when I get mine on the street. I don't think I can get it out the back.... Darn

 

[SUPERSTOCKRACER]

Believe it or not I picked up when I installed my exhaust on my 65 Hemi Belvedere. It liked the backpressure. I ran 3.5" through Dynomax mufflers.

 

[daniel_depetro]

We had a 1970 Charger with an exhaust the stopped just before the rear axle with turndowns. Never again. Way too much noise and everytime you got near any dirt it kicked it up all over the car/interior.


We have dual 3" on our 1972 Dodge Dart and the car loves it.
Looks tough and sounds great.
We bent it ourselves on a standard (non mandrel bends) exhaust shop digital pipe bender. We used as few bends as we could be and kept all the bends as wide (not sharp/tight) as possible.
Still need to add 'H' or 'X' pipe.

Now I need to replace the 1-7/8" dual exhaust pipe on the 1968 Coronet coupe so it's mildly built 440/4-speed can be a bit more fun to drive.

 

[HEMI-ITIS]

I had a 3.5 system before the 4 inch.The exhaust was pretty muffled,but I love the way the sounds with the "X" pipe.You can barley hear my street car at the track next to the race cars.But once I "GIT GOIN" it might get your attention:icon_hang::sleepy2:

 

[beezee]

I,m running a TTI exhaust,2" headers into 3" exhaust to the tips,no problems in fitment.Did have to install a torque strap as the collector was tapping the cross member.

 

[HEMI-ITIS]

Thanks HEMI-ITIS! My roadrunner has only been on 1/8 tracks and it is good for 6.90's We drive it hundreds of miles on our outings so the fumes are a problem. That is a great looking Beast you have there I might add!!!!

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I agree... Nice for sure. I have a four link and I wonder about the exhaust problem when I get mine on the street. I don't think I can get it out the back.... Darn

Thank you guys for your kind words:icon_salut::bighug:

 

[ykf7b0]

Quote: Daniel Depetro; Now I need to replace the 1-7/8" dual exhaust pipe on the 1968 Coronet coupe so it's mildly built 440/4-speed can be a bit more fun to drive.





Dang. they do look really small!

 

[9secondsatellite]

are you running a pcv? what are you using to evac the crankcase? what cubic inch and at what max rpm? 3" should be fine but might be over kill with your application.

 

[dbowperson]

If you're running a basically stock engine you most likely won't see much if any gain. In fact, a stock 440 typically runs best with 2 1/2" pipes. However, the 3" pipes will give you a better sound, especially if you run an X-pipe.

 

[ykf7b0]

I have had the 3 inch with turndowns at the rear axle for almost ten years. Engine is not stock and the roadrunner is running 10's on the bottle and mid 11's on motor. I was questioning if anyone was having clearance problems with bigger tailpipes over the rear axle because I'm in the process of running the exaust all the way out to eliminate exhuast fumes inside the car.

 

[dbowperson]

I see. 3" should be no problem. I've seen quite a few cars with 3" all the way back with no clearance issues.

 

[68X426]

Hey ykf7b0, I'm your Road Runner cousin.

Mine is a 68 RR, 505 Hemi, TTI headers and collectors, TTI 3 inch exhaust, H-pipe crossover, Dougs 3" electric cutouts, just in front of DynoMax Super Turbos, then 3 inch to the stainless tips. Works perfectly, lots of room, room for the Gear Vendors overdrive as well.

I haven't had a fume problem with the cutouts (my wife has "the" problem with "the" smells we know that goes). Really, no fume issue because they aim outward, perpendicular to the ground. If the outlet is at any angle other than zero degrees it'll generate fumes, dust, and no fun. Same for any outlet anywhere before the bumper.

 

[9secondsatellite]

Hey ykf7b0, I'm your Road Runner cousin.

Mine is a 68 RR, 505 Hemi, TTI headers and collectors, TTI 3 inch exhaust, H-pipe crossover, Dougs 3" electric cutouts, just in front of DynoMax Super Turbos, then 3 inch to the stainless tips. Works perfectly, lots of room, room for the Gear Vendors overdrive as well.

I haven't had a fume problem with the cutouts (my wife has "the" problem with "the" smells we know that goes). Really, no fume issue because they aim outward, perpendicular to the ground. If the outlet is at any angle other than zero degrees it'll generate fumes, dust, and no fun. Same for any outlet anywhere before the bumper.

nice car!

 

[Stumper]

Shoot, my fumes are bad in the car with full exhaust out the back. I'm running 3" tubes and Delta 50 mufflers. Can anyone tell me what benefit I would gain from an H pipe? Do they really result in power gains?

 

[dbowperson]

From what I have seen there is no performance gain with an H-Pipe, but it will give you a better sound. If you're looking for performance, then you want an X-Pipe, but that is very debatable as to how much. I think a lot of places will say 15-20 HP, but that could be a stretch. You will not get optimal performance from a one-size-fits-all kit. The actual location of the X-Pipe with regards to distance from the engine will affect the results. The kits are designed more for ease of installation and clearance than they are for performance.

 

[ykf7b0]

Hey ykf7b0, I'm your Road Runner cousin.

Mine is a 68 RR, 505 Hemi, TTI headers and collectors, TTI 3 inch exhaust, H-pipe crossover, Dougs 3" electric cutouts, just in front of DynoMax Super Turbos, then 3 inch to the stainless tips. Works perfectly, lots of room, room for the Gear Vendors overdrive as well.

Thanks Cuz!!! That is a beautiful 68!!! Has it been on the drag strip?

 

[696pack]

From what I have seen there is no performance gain with an H-Pipe, but it will give you a better sound. If you're looking for performance, then you want an X-Pipe, but that is very debatable as to how much. I think a lot of places will say 15-20 HP, but that could be a stretch. You will not get optimal performance from a one-size-fits-all kit. The actual location of the X-Pipe with regards to distance from the engine will affect the results. The kits are designed more for ease of installation and clearance than they are for performance.

That would be a BIG stretch in my opinion.