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Unread 08-20-2015, 06:44 PM   #1
Galligher
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1995 YJ Wrangler 
 
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Exhaust tailpipe for SBC swap

I am in the final steps of swapping a 330hp vortec headed 350 into my 1995 Wrangler. I have 2.5" ramhorn exhaust manifolds with 2.5" downpipes that y into a single 3" pipe. My question is after the muffler. Fitting a 3" tailpipe does not look possible. I don't want turndowns or a side exit as I want it to be as streetable as possible. I am thinking it may not be a big deal to have a 2.5" tailpipe and not drop hp by more than a couple. My thought is that the difference in size is 70% (2.5 of 3 in area of a circle). Bringing out the science major in myself, Charles law states that temp and volume are proportional in gases. I am thinking that after the muffler, the temp drop from the start of the y to the back of the muffler has to be 70% drop in temp. If this really is true, that the actual change in size of the exhaust really doesn't change. The potential is that it may increase torque in that exhaust velocity is maintained? Any thoughts?

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Unread 08-21-2015, 09:31 AM   #2
Randonexplosion
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I honestly have no input on the science but I am running 2.5" exhaust with my 5.3 and it is fine, though I am more interested in low end power.
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Unread 08-21-2015, 03:18 PM   #3
gotswap
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would something like this help move it out a bit?

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Unread 08-21-2015, 04:03 PM   #4
87TPIYJ
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I have the 2.5" ramshorns and a ypipe. My entire exhaust is 2.5". Mine goes manifold, Y pipe, cat, straight shot to muffler (single in dual out) then tail pipes coming out at a 45 in front of the shackle between the frame and leaf. Here are some pics from when I was building it. Hope this helps.














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Unread 08-21-2015, 04:06 PM   #5
zte87
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I am running 3 inch out the back In the stock location So it's possible. I am running 2.5 for the y pipe than 3 inch from there back (high flow cat/ flowmaster ). It's tight but doable!
image-3786950412.jpg

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Unread 08-21-2015, 07:49 PM   #6
Galligher
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87TPIYJ - Thanks, I thought about running the exhaust out back like yours, through the frame and springs. Have you had any issue of the springs touching. I am SUA though so some differences in spacing. Also, it looks in the pic that the exhaust is pointed at the tire, any issues?

GOTSWAP - Any issues touching the springs? Looks like your lift is big enough that it probably is not an issue. The pipe looks like a "stockish" 2.25" one, but I could be wrong.

ZTE87 - That is great! It is tight but it looks like you have some spacing on both sides. How was the clearance for the 3" pipe over the axle?

Again, thanks! I may go 3" out back if over the axle is not bad, or maybe 3" between the frame and springs... Either would be more quiet than out the side or turndowns and the smell would probably not be much different than the stock motor/exhaust.
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Unread 08-21-2015, 08:14 PM   #7
zte87
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Quote:
Originally Posted by Galligher
87TPIYJ - Thanks, I thought about running the exhaust out back like yours, through the frame and springs. Have you had any issue of the springs touching. I am SUA though so some differences in spacing. Also, it looks in the pic that the exhaust is pointed at the tire, any issues? GOTSWAP - Any issues touching the springs? Looks like your lift is big enough that it probably is not an issue. The pipe looks like a "stockish" 2.25" one, but I could be wrong. ZTE87 - That is great! It is tight but it looks like you have some spacing on both sides. How was the clearance for the 3" pipe over the axle? Again, thanks! I may go 3" out back if over the axle is not bad, or maybe 3" between the frame and springs... Either would be more quiet than out the side or turndowns and the smell would probably not be much different than the stock motor/exhaust.
It's very close, it's up high enough to where my bump stops keep my axle off it at full flex. It was dumped under the tub before and I hated it!

Updated with a pic, it barley contacts the axle under full flex (as I said all ready my bump stop prevents this). And I am soa with stock frenched springs......I imagine you would be better off with arched sua setup!
image-1685121588.jpg

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Unread 08-21-2015, 08:30 PM   #8
stevehoj
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I also run a mandrel bent 3" tailpipe for YJ and stock location. Call below.

http://www.kolakperformance.com/

Happy motoring.
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Unread 08-22-2015, 08:04 AM   #9
87TPIYJ
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It's the illusion of the picture. It's really at a 45 pointing towards the back past the tire. The spring never contacts the exhaust, however at full stuffy tire will touch the tail pipe on one side. I could fix it where it wouldn't, but just been to lazy to.


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Unread 08-22-2015, 02:48 PM   #10
gotswap
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I think I have pretty much stock diameter pipe but am no where near close to touching anywhere under full stuff. If you want I can go out and take some better pics.
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Unread 08-22-2015, 04:38 PM   #11
Galligher
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Thanks to all! I see I have many good options.
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