Hans4real

Where did you get the pre-bent mandrel bent pipes?

MotorHead

That is how most of the HP 3 inch systems are done. They use prebent mandrel 3" tubes for the bends and butt weld everything together. Up on a hoist it is pretty much a no brainer for a good exhuast shop and the difference in coin and agony of trying to do it yourself is worth the extra cost if there is any.

As most C3's are slightly different it is better to have the exhaust fabricated to the car rather than buying some kit and lying on your back trying to make it fit. Find a good custom exhaust shop and spend a bit more and you will be much happier.

BTW you don't need 3 inch until you reach at least 500HP crank HP, but if your planning to increase your existing HP then do it once with the 3 inch

roscobbc

When I replaced the 1 7/8" id Hedmans with 2 1/8" Super Comps I had a custom 3" stainless system with 'X' pipe made up for the car. It was really surprising how much the 'top end' opened up - it would always runs to 6500 rpm - now it 'leaps' to 6500 rpm and wants to go further.
http://s160.photobucket.com/albums/t...t=DSCF1411.jpg
Shaky phone clip.
http://s160.photobucket.com/albums/t...t=IMG_0621.mp4

Hans4real

I'm in the 450 HP range and I made the commitment on size today by ordering the 3" Dynomax Ultraflows 17221. Now I'm stuck with choosing an X-pipe set-up or H-Pipe deal. Read too many threads on this forum and others and some say X and some say H, confusing. I'm not sure if the location, being so far back for both set-ups, favors one or the other. Also read that if an X isn't done correctly it can actually hurt the performance. I haven't heard that same comment about the H. There are also several X designs to select from, you have the Flowmaster, Magnaflow, Pypes and then the Summit brand. Any advice on the choice would be appreciated.

Les

Since I'm on the verge of getting a mandrel system that has an X-pipe built into it, I read about H vs X for a good 2-3 hours last night. Most sources say the X-pipe has a slight power advantage but the difference is minimal. Just about everybody agrees that there's a notable difference in sound between the two. I listened to a lot of youtube vids comparing the two, and there is no doubt a different tone. The H pipe has a bit deeper sound whereas the X is crisper and a bit higher pitched, especially at higher RPMs. The consensus seems to be that both styles should ideally be positioned as far upstream as possible, understanding that space limitations can play a big role regarding location.

Since performance is so close, the decision between the two largely comes down to sound preference. This appeared to be split pretty evenly. One guy had an interesting comment that I think is right on the money. His comment was about how muffler choice plays a role in that. He said the chambered style mufflers sound better with the H style- X just doesn't sound as good. Other than that he prefers the X sound.

I finally refined my search and found the video that eased my concerns about changing from H to X. This 454 Chevelle has Dynomax Ultraflo mufflers like you and I do and it also has an X-pipe. I think his car sounds awesome. Although he's probably got more cam than either of us, this should give you a pretty good idea of what your car would sound like with the X.

cv67

ALso running the same 17547 all 3" with X.
The X I doubt gave it any power but did dumb down the crackly higher pitched noises that the man will hear 3 blocks away . Goal was to quiet it down...1 muffler I know of is quieter but not sure I want a power loss...on the street probably never notice it . Oh well.
Mic is too high on the camera sounds louder than it is. With the windows up you dont hear much at all, down different story.

They make an oval type Ultraflow which is more crackly sounding make sure you get the right ones.

These sound incredible at 4k on up, a real clean metallic screaming banshee noise is the only way to describe it

http://www.youtube.com/watch?v=941Qis8BG9U

Hans4real

Appreciate the sound clip and that Chevelle sounds reallly good. With the 454 I think I'll prefer as low a rumble as possible and if the power output is close to the same, think I'm leaning towards the H pipe. That X setup sounds a little Euro up in the RPM, like a Ferrari. Good luck with your new system install. Swap you sound clips when we're finished.

gkull

Mandrel bending is not a must in a 3 inch system. If you use a pass under cross member and run the 3 inch pipes straight back from the headers the gasses are cooling the farther away from the engine you get.

I have a 4 inch ovalled H pipe welded in right below the diff. where the pipes are closest together