Alright my turn to ask the same question that has been asked 1,000x's. I am thankfully going to finally be getting a new exhaust on my 1972 Cutlass with a stock 455 and am still trying to make up my mind on the final details. I have been shopping around for awhile and I believe I am going for a 2.5" aluminized with Dynomax's. But I still have the nagging question of either an x-pipe, h-pipe or niether. Alot of you guys recommend the x for better flowing and performance, while some from other various auto forums say the h for lower end torque and a deeper sound. Now being honest with myself, my engine is pretty tired and I really don't think a lose or gain of 10-20 HP will be that noticeable ( I will just get a K & N filter to make it up ) so I am focusing on the sound. Right now I have the stock 2.25" tubes from the engine frenched into 3" pipes right before the mufflers with no welding or clamps, just shoved right into it (thanks previous owner). It is so loud and annoying and raspy and uneven that ANYTHING would be 1,000x's better as long as it is sealed up. So what should I do? I am not concerned about the price very much, I just want it to be nice and effective. After speaking to one of my local mom and pop exhaust shops the "expert" that has been doing this for 20 years said he is tired of people asking for x or h pipes because they don't do anything for street driven cars, only hi-revving racecars. He said all they do is make it a bitch to do any transmission work and the pipe would have to be cut out to actually do any transmission work. The guy seemed like a spaz and his way was the only way, but I have known people that have gone to him for many years and said he is the best. But I have descided on a smaller local shop that is much more open to my wants and concerns and is not telling me what I need but asking what I want. Anyway, h-pipe, y-pipe, figure 8 pipe....??? Need to know before tomorrow because it's D-day or I should say E-day.

 

I think you have the right idea going to a different shop. I had a local exhaust shop install an X pipe when they did my pipes. I guess it gives a mellower sound. I did it becaue it was only $60 extra.

I've also heard that an H pipe is better for low end torque. I don't know if it is true or not. Whatever you get I think you will be happy with it. Especially if your running "hill billy" exhaust right now.

 

Whatever your choice, have it done by someone who will do it your way.

 

Either configuration allows stacked exhaust pulses a place to go, relieving back pressure. I put the crossover behind the trans. ...

 

I know it is a little late in this ballgame, but check the Summit website and read up on the different types (H, X, 2.5", 3", etc). Use it as a reference to find the one that fits your wants best.
I have H pipes 2.25" on my 455. It is doing fine.

 

Yeah hillbilly exhaust is an understatement. I have been looking all over the Internet, through articles, watching videos on YouTube and it seems like the consensus is there is not a huge difference between the 2, at least at my power level. You are talking maybe 7-10 hp/ft lbs of torque? Not a big deal for me. But there seems to be a fairly noticable difference in the sound. The x pipe seems to be a more mellow, highly tuned growl as opposed to the H pipe that has the lower ragged muscle car sound. I personally like the lower grumble so I am leaning toward the H. I can't believe how big of a topic this is on the Internet. There are forums all over the place where people are fighting with each other over which is better.... X gives more HP, well H gives more torque, they are the same, they are totally different, well your mom's a hag. I mean it is like a bunch of highschool kids. Most of the bickering is going on in the Mustank 5.0 forums so they probably are highschool kids.. Well I am going to sleep on it, and probably change my mind 8 times on the drive up to the shop. We will see tomorrow!

 

As some have already noted, the performance gain differenced between an H-Pipe and an X-pipe are pretty minor- especially for a street driven car.
Your Butt-Dyno will not be able to tell the difference, though at the track you likley would see a couple tenths + MPH increase by going with the X pipe.

As for sound. I had an X-pipe once. Won't do it again. The sound was not my cup of tea.

Made a Small block chevy i had sound like a V6 car. Definitely quieter-Higher pitched and smoother.

I had it cut off and replaced with regular duals after about 6 months.

I find H-pipes have a slightly smoother tone than straight duals- but it doesn't drasticly change the sound like the X does.

Comparing Exhaust sound is tough- Even on cars with the same mufflers, the sound can be radically different based on the engines compression ratio- header type (coated Vs Not coated, Full length vs Shorty, & primary pipe guage) head pipe size & design, tailpipe size, etc etc.

 

Well just got back from the exhaust shop and didn't get it done yet. The guy who will be doing the system is about to go on vacation this week. He didn't tell me that when I spoke to him last week, but oh well, that's what happens when you go to such a small shop. But I was very happy after speaking to him. He has had 3 Oldsmobiles in his 40 sum years, 2 Cutlass with 350s and a 1970 442 w/ a 455. So he is in tune with what I want. He said if my engine was running top notch, he would just do straight pipes, but since it is a pretty tired stock engine it should greatly benefit with an h pipe. As for the mufflers, I threw out the Dynomax turbo ideas and he said he could do them but it would take the price up from the $400 he quoted me. His quote included some "white box" performance mufflers that are Flowmaster knockoffs. They look just like FM's but he said they are a lot mellower, not nearly as annoying. Even though he "specializes" in Flowmaster systems, he said that he has not used them in over 5 years because these knockoffs are cheap and sound a lot better. He said they sound a lot like the Thrush flowmaster knockoffs, but not as loud. So I am excited. Now I just have to wait a whole week to take it back up. In the meantime, after driving it around all day and making a few stops, I am having a new never before seen issue that I am going to start a new post for.

 

Good to hear that you will get the exhaust done soon. Keep us posted.