2.5" or 3"

[Dome]

Whats the conensus?? I'm going to be replacing my exhaust system in the very near future. Oh, and I have a 2bbl 360 if that makes a difference.

[Kris]

Hi Adam...
I went with 2.5" and a 50 series Flowmaster and am quite happy.
The 3" would look cooler, but the gain would not be noticeable on a stock engine. I know there is someone here that went 3" but said that it got really tight going over the rear axle. Your SOA might alieviate this though. A friend of mine put a 3" 50 series Flowmaster on his Dodge p/u and it was noticibly quiter than mine. We figured that the larger pipe was slowing the exhaust pulse down.

$.02 ?

kris.

[mahlmann]

For the kind of low revs our FSJ's crank, I doubt that the 3" system would provide any measurable benefit over a 2.5" system. Now, bragging rights are another area and 3" just sounds better than 2.5"!

People are usually going to tell you they like whatever they have or did. I've got 2.5" systems on my 360CID Waggy and my 402CID 400HP Chevelle. I don't think either one is limited by the performance of the exhaust system.

-Mike A.

'87 Grand "Steel Brick"
Sunnyvale, CA

[Joker]

I just went with 3' with Flowmaster and where it sounds great I doubt it improved my performance whole lot versus 2.5. But still it sounds aewsome and it gives it the "Big Truck" look. In my case the cost wasn't much more going with the 3 in. Thats just my 2 Abe's worth.

[ArtsiFrtsi]

Even though I can't compare my performance to a stock motor in my rig, I do like the dual 2.5 inch exhaust. It goes to a dual in, dual out Flowmaster muffler, and is quieter than the exhaust in wifies Chero... until I hit the gas!

[blt2krl]

I like the 3in I just got on my rig. No complaints as far as performance losses in comparison to the duals I had removed.

[Dive 30]

I went from Headers (Hedman $99) to 2.5" flex pipes ($9.00 Autozone) and 2.5" cherry bomb glass packs ($15.00 Autozone)to a custom bent single 2.5", no cat, to a 14" Super Turbo. The guys at the shop (good bunch too, do lots of custom work) said that on the 360 a 3" really wouldn't gain me that much. I love the way mine sounds (especially the look on the unsuspecting punk SUV owners that try and beat me off the line) when I romp on it, the exhaust roars and I chirp the rears off the line. It is a loss in overall performance from my improvised (though audibly kick a$$ loud, cool and intolerable) exhaust. Mine cost $250.00 . . . kind of pricey.

Adam . . . I would talk to Ken's Muffler on North College. They usually pitch some attitude, but they make excellent systems for a fair price. They just initially try to talk you out of a custom set-up.

[Lindel]

You certainly aren't going to gain enough using a 3" system to justify the cost, over a 2.5", or even a 2.25" system, especially with duals.

With a single, the 2.5 would be sufficient, and cost a lot less than the comparable 3" system would.

[Lindel]

Remember, the road to torque, which is what we want for off road, and towing, is to keep the gasses flowing at the highest possible speed, and a relatively "smaller" intake/exhaust will do that for us.

By smaller, I don't mean to the point that the engine gets choked, but a 2.5" single, or a 2.25" dual system is all that's necessary. I don't think that bumping up one more size on either will hurt, at least nothing aside from the pocket book.

[blt2krl]

I have to disagree on the cost issue, at least in my area. The whole 3 in system cost $270 a 2.5 cost only $240. Of only a savings of 30 dollars, I decided to go ahead and do the 3in. The only other reasoning I had was that since the whole system had to be built and bent at the shop and all the bends would be at about 2.5 in. I thought it better to start out with the larger diameter. Like I said before I had 2.25 duals and there was a significant gain going to the 3in. I'm not advicating that 3in is the only and ideal way to go. I'm just stating I'm happy with the results I have obtained.

[rigger]

i love my 3" it just sound sweet

[Millerluck]

I was recomended 3" by Thorley.

As far as price I know the guy at the muffler shop.

And yes I did drive right infront of the police station with open headers to drop it off.

The sound is sweet with a Flowmaster 50! Great rumble to it when you get on it.


Later

Larry Miller

[Kenall]

well with all the rocks iv gone over having a madrel bent $$$ ex system that i wood ahve to repair over n over , was not the ticket.

sooooo im using the jc whitney bendable stuff and have been for 9 years. ez to fix and rebend out of the way of this part or that part.

im running dual 2" with equal length pipe b4 and after the muffs. 2" is small, but it slides over the leeder pipes descending from the OE ex manis.

100$ for 25' of tubing, 40$ for the muffs, 20$ for clamps and such.

one thing tho...the dual system i installed to replace the single system i had b4 of the same size/material is much louder. y wood the duals be louder than the single??

[Lindel]

Ken, it's probably as much the quality of the pipe, as anything else. I've had duals on hipo cars, that weren't as loud as the single with glass pack on my Cherokee.

Then again, the exhaust on my Chero is a real hodge podge at the moment. I will be fixing this in the near future.

[243]

Take a look at the cross sectional area of typical straight pipe used in exhaust systems:

2" = 3.14 sq.in. Dual = 6.18

2.25" = 3.98 sq. in. Dual = 7.96

2.5" = 4.91 sq. in. Dual = 9.82

3" = 7.07 sq. in.

A dual 2.5" has greater cross section area than a single 3" and not by a wide margin. A single 2.5" is has a little more than half the cross sectional area of the 3".