I know what you're saying. That's the same basic formula as Ohms law. Here's my thought. Dual exhaust with 2.25" is more then sufficient. That's good to around 450-500 hp. The CSA area of two 2.25" pipe is the same as one 3" pipe. While in theory it should effect flow, you have more then enough area.

Hot Rod Magazine actually did a test on dinging and flattening header tubes for clearance. They literally took a 10 pound sledgehammer and beat the daylights out of the tubes including using the wedge side. It hardly effected power. Don't forget the hotter the exhaust gases, the smaller the pipe it needs.

With a 3" pipe I would imagine you could need a few flat spots for clearance. As long as it was done neatly it wouldn't bother me. I'd rather have that then from hitting the road. Besides even if it did effect performance it wouldn't be in everyday driving


https://www.dailymotion.com/video/x3vupq0

Last edited by Huskinhano (5/07/2020 10:55 AM)

That looks like some of my handy work...;)  

It definitely doesn't make a difference in power.  I think given the size of the pipe any backpressure change will be minimal. 

Should you be pissed?  I guess it depends.  Stuff like this is exactly why I don't have other people work on my vehicles.  If I have to make a compromise like this at least I know I explored every possible avenue before making it.  I get that I should give others the benefit of that doubt, but I find it hard. 

From his perspective, he's been doing this for however long and probably had very few complaints about stuff like this over the years.  Does that make it right?  Again, I guess it depends.

Ultimately should or shouldn't you be pissed doesn't really matter; you are pissed.  The question becomes how to handle it.  If it bothers you that much I think I'd get it fixed, either have him do it or someone else.  I have to say I'm a believer in the statement that its not about never making mistakes or having problems arise; its about how you handle those things when they do.  As a business owner I'd like to have the opportunity to make a customer happy and have them talking about how I fixed the problem, not how I screwed it up. 

Like the famous and well known  'sage'  once said............"Ah-simma-down-now.....ah-sima-DOWN-now.....Ah-simma.......-down....-NOW............Ah-simma-down-now!"    The late  Rosanna-Rosanna-danna. RIP

You think THAT'S bent up??!!!    You should see the BFH job I had to do on my pipes.(only difference is...I did it....you paid somebody to beat on yours)
No kidd'in  what you got looks fine.
  Maybe there is a difference in 'fluid' vs gases?!    Once spoken by the man who took a laxative before going to bed! Hence the term  "my so & so just  $hit-the-bed"!

Don't worry about it.......just drive the fool out-of-it.....you'll feel better!
6sally6

Looks like a good job of clearancing. Find the Hot Rod article and look at THEIR hammer work.  Then see their dyno results that showed no discernible difference.

I’d say your right to be angry depends on what you spent.

If you handed the guy $1000-2000 Labor for a mandrel bent 2 day long job worthy of a SEMA car - then yes.

If you handed over $400 labor for a decent driver quality exhaust - then no.

Putting 3” pipe on a Mustang is going to require sacrifices of some sort, ground clearance or pipe shape- even 2.5” pipe can be a pain.  There are some pretty wild “clearance” pipes out there that are manufactured to allow the same area as a 3” pipe, but in all sorts of funky shapes.  Maybe one of those options would better suit you?