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  #1  
Old 08-23-2012, 08:02 PM
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HerrKooled HerrKooled is offline
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5" MBRP exhaust on J truck w/ cummins?

Question for you guys who did the conversion, I'm ordering my exhaust for the J20, however what did you use for your exhaust? Can you order something for a 94-02 Ram truck and make it fit? No one around here can custom bend 4" or 5" and I'd like to buy their entire turbo back system if i can make it work, as I love the way they sound on 12V's, performance boost and keep the EGT's down.

Thanks
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Old 08-24-2012, 06:02 AM
wap wap is offline
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If you want 5" for the way it looks, sounds, or just to say you have 5" then get it. However you will notice no performance gain unless you are making major power. I know of guys making over 700hp on 4" exhaust and while I have never dynoed mine I have a healthy set of twins (64mm s300 over s476) and run a 4" DP into 5 because I like the way the 5" sounds. The twins are shipped with the 4" DP from a company that knows much more about what exhaust will work best for said turbos than I. Furthermore 5" will be harder to package just FYI.

I have put on plenty of exhausts and for the most part after the DP they are all the same from the DP to the over axle pipe just with different hangers. If you can weld or fab at all you should be fine with any exhaust just get them with the clamp on hangers so you can move them and be prepared to cut and modify as necessary. If the DP will clear your fire wall you should be fine. Never worked on a cummins that wasnt in a dodge but if your DP works the rest can be modified easy enough.
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Old 08-24-2012, 08:23 AM
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I have a complete 4" system for my swap that came out of a Dodge. I've taken various measurements and see no reason why they won't all fit into my truck with some cutting, fab'ing, and rewelding. I'll probably be getting to it in the next few weeks and will post pics.

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Old 08-24-2012, 03:46 PM
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Mikel Mikel is offline
 
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My vote too on 5" being too big unless you are making mega-HP. I'm perfectly happy with my 3" exhaust and a tweaked P-pump.
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  #5  
Old 05-29-2013, 06:06 PM
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HerrKooled HerrKooled is offline
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Quote:
Originally Posted by wap
If you want 5" for the way it looks, sounds, or just to say you have 5" then get it. However you will notice no performance gain unless you are making major power. I know of guys making over 700hp on 4" exhaust and while I have never dynoed mine I have a healthy set of twins (64mm s300 over s476) and run a 4" DP into 5 because I like the way the 5" sounds. The twins are shipped with the 4" DP from a company that knows much more about what exhaust will work best for said turbos than I. Furthermore 5" will be harder to package just FYI.

I have put on plenty of exhausts and for the most part after the DP they are all the same from the DP to the over axle pipe just with different hangers. If you can weld or fab at all you should be fine with any exhaust just get them with the clamp on hangers so you can move them and be prepared to cut and modify as necessary. If the DP will clear your fire wall you should be fine. Never worked on a cummins that wasnt in a dodge but if your DP works the rest can be modified easy enough.

Sorry for the late reply, does the 5" give more "bass" then the 4"? I run 3" duals on my BBC chevelle at just over 600 horse and it flows great from the headers and the sound has that deep bass you feel in your chest. I'd like the same from the J truck. The P pump 12V I have for it makes just over 800 ft lbs with bigger turbo, injectors and fuel plate however I will be bumping it up to around 1000 ft lbs. Obviously horsepower is way lower on a diesel, but I'm not building it for HP.
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Old 05-29-2013, 06:32 PM
joe joe is offline
 
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Dsl's do like big exh pipes..."within reason." I'm no pro gaso or dsl wrench but 4" works really well with Ford and GM pickup truck dsl's. 3 inch also works just fine. Only reason I see for going 5" culvert pipe is the "wannabe trucker look".
Catalog marketing hype only makes you go faster cause you're hauling less weight...lighter wallet.
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Old 05-29-2013, 07:04 PM
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Makes sense, however I always see the wannabe trucker look as running stacks. I have people tell me to run stacks and I think they would be hideous on a J truck. I have a buddy who is running 3.5" exhaust on his 68 coronet at around 740 horse, and I actually don't like the sound but he says it flows as if no exhaust is on the car - same diameter as headers. I'll probably go with 4" but I'll have to hear a 4" and 5" cummins trucks sitting right next to each other to hear if there is a difference.
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Old 06-01-2013, 12:28 PM
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i know it is a little different of an animal. my 04.5 cummins had a 4 in. strait pipe. a crappy weld broke and the front of the pipe hit the ground. i replaced it with a full 5" strait pipe set up. the new pipe is WAY louder than the 4". did it help with performance? highly doubt it. does it sound the way i want? yup. does it bother my nabors when i go to work at 4:30 am? yes sir! with that said that is a BIG pipe in what is probably a tight space to start with.
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Old 07-11-2013, 06:57 PM
Mudbull Mudbull is offline
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Not sure if I have good pics, but w/ the firewall shaved theres tons of room for my 4" pipe on my truck. It is a fabbed downpipe, the aftermarket dodge ram dp doesn't is too sloped back and was hitting the footwell.

In the above pic is the 4" Ram DP...you need to get rid of that 'diagonal kink' and let it drop straight down till its below the floor. the cab is on the lift in this pic still ~3" off the frame so the space is decieving

New piping, flange from 4" Ram pipe.
I understand people not liking stacks, but I think I can make it work, running it through the bedside. I loved how the 4" into 6" stack sounded on my donor.
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  #10  
Old 07-11-2013, 08:05 PM
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You would probably be better off ordering something with around the same wheel base so your bends may end up in or around where you need them and may be able to make it fit with little mods maybe just move the hangers. And if you want 5" get it ill tell it will be loud my buddy had a 24v with straight 5" no muffler and when he passed a cop he had to shut his truck off because they would pull him over for noise
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  #11  
Old 07-13-2013, 08:43 AM
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mcjeep80 mcjeep80 is offline
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not many bends on a cummins exh. rollinsmokediesel.com has great prices. the kit i got was a down pipe, tail pipe. cat del. and like 6' of strait pipe. realy simple system
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35x12.5x16.5 thorn turds

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  #12  
Old 07-15-2013, 12:20 AM
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HerrKooled HerrKooled is offline
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Mudbull looks great! Did you just set the Jeep on the Ram frame? I'm thinking of doing that. Could convert my truck into dually easily doing that as my doner is a 97 3500.
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  #13  
Old 08-12-2013, 07:12 PM
Mudbull Mudbull is offline
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Quote:
Originally Posted by HerrKooled
Mudbull looks great! Did you just set the Jeep on the Ram frame? I'm thinking of doing that. Could convert my truck into dually easily doing that as my doner is a 97 3500.

Thanks! My donor was a 96 ram 3500 dually. The owner had already removed the dually front spacers and rear wheels/fenders when I got it. The dually rear axle has bigger drum brakes (to my knowledge) but it is only a couple inches wider than a non-dually.

I got a donor frame that we shortened to 120" wheelbase (as opposed to the dually 154") Otherwise it is a stock ram frame that we dropped the Kaiser body onto (w/ ram mounts relocated of course)
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Old 08-14-2013, 06:11 AM
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If your truck is a passenger drop, you are going to have some clearance issues at the transfer case and crossmember. It was already a tight fit with a 4"
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