2.25" or 2.5" exhaust?

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1967DartGT

1967DartGT

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I just got a set of older Doug's Headers and am trying to plan out the exhaust system for my 67 Dart. I'll be running dual exhaust of course but was wondering what pipe size that you would recommend for a street built 273. I was leaning towards 2.25" but was also considering 2.5". There is the possiblity that I could eventually put a hotter 318 in it (for no other reason than that I have a couple of 318 blocks sitting around itching to do something) but probably nothing bigger than the 273 or 318. The headers have 2.5" collectors.
Thanks
Kevin
 
2.25 is all you need for smaller engines. The 2.5 sound deeper but if you put too big an exhaust on you could potentially hurt torque/performance.
 
I vote for 2.5"

a single stick of 2.5" has a flow capacity of about 330hp airflow wise....with 2.5" duals and your statement that you will run a 273/318 forever...you will never outflow the capabilty of 650hp of air that the 2.5" pipes can handle.

2.25 will limit you to 450-500hp before it becomes a restriction.

How do I know all this? My turbo 4 cylinder days recall clearly the .70 second gain I recieved by installing a SINGLE 3" exhaust pipe over the aftermarket 2.5" I put on a year before, and 2.5 seconds faster than it would go with the stock 2" exhaust system.

Trap speeds prove I was making notable Hp gains:

1998 Eclipse GSX Awd Turbo

100% Stock - 10 psi boost - 14.97 @ 88 mph

Stock Engine and exhaust, upgrade turbo 16 psi - 14.3 @ 94

Stock Engine, 2.5" exhaust, 16 psi, - 14.0 @ 97

Stock Engine, 850cc injectors, Front Mounted Intercooler, 22 psi, 3" exhaust 13.31 @ 107

THEN,...Customized Programmable ECU,Two Step Rev Limiter, 15 psi @ 6000 launch, 25 psi - 12.74 @ 112

http://www.youtube.com/watch?v=unL4IIMMlxg

Nuff said.
 
There is a gain in going from 2-1/4 to 2-1/2 at the 300 HP level. Not much, but, you will notice a sound jump as well.
How much power are you making?
 
While 2.25" may be adequate, if the cost is similar go with the 2.5" pipes. Unless they are mandrel bent the pipes will be smashed down to 2.25" at each significant bend anyhow. Larger diameter pipes will tend to be a bit louder with the same muffler, but will have a nicer tone. If you want pipes that "snap" go with a smaller diameter.

If your muffler guy tells you that you should run the smaller pipe because "your engine needs some back pressure" he is lying to you (although he may be too stupid to know it). Take your business elsewhere.
 
Quote ... "If your muffler guy tells you that you should run the smaller pipe because "your engine needs some back pressure" he is lying to you (although he may be too stupid to know it). Take your business elsewhere."

Yah, there is one muffler guy that I won't take this car to because he wanted to put in 2" because he said there was not enough room for anything larger when going over the rear axles on "these old Dodges". He must have been a chevy guy trying to even the playing field!
 
Purchase a summitt racing 3 inch system and show'em the truth with a big burnout in his shops driveway. LOL
 
if i would have been the guy building your exhaust you can be sure i would have made it out of 2½ mandrelbent tubing mostly because it will give you some extra room for future upgrades and it will sound alitle bigger and alitle deeper (remember i wrote sound alitle bigger not louder) just the way i like it:)

and to those saying bigger exhaust will kill torque i dont believe in it, bigger primarys in the headers may kill torque but thats a diferet story
 
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