Exhaust suggestions

[afterglow]

I need some help deciding which way to go for my exhaust.

I have a 69 Mach 1 and it's in the midst of an engine/drivetrain upgrade. A 408w roller engine is going in, HR cam, etc. It should be right around 500hp/500 ft.lbs at the flywheel. Most of the power will be down low and I don't expect to spin her past 6000 or 6500.

I'll be going with 1-3/4" long tubes and 3" exhaust for this one but need help deciding which way to go with the design as everything will be custom. X-pipe? H-pipe? Dumps? Straight through?

Loudness isn't much of an issue but I don't want it to be irritating while cruising. It's going to be a 100% street car. Cats are also optional

 

[dcstang67]

I have a Magnaflow system on my car with an X-pipe. I love the way it sounds, much quieter in the cabin at cruising than my Flowmaster and when you get on it it really sounds good. It has a nice sound at idle too. Another bonus is that it is stainless.

 

[2+2GT]

It really doesn't make much difference, although I suspect the H is slightly better than the X. At least that's what the guys at Pypes told me when I asked them the same question. Mostly the X is fashionable.

What's more important is how close it is to the engine, and it's easier to get the H closer. Fuelie Corvettes actually wrapped the crosstube under the engine, it couldn't have been closer.

 

[65FBE2]

I have Flow masters with a X pipe 2.5" all the way back. Sound is great and not bad cruisin. I do have Flow Master 50's not 40's though. I'm thinking of going with 1 3/4" headers myself, What headers do you have. And how much did they cost you. All I can find start at about $850 and go up from there.

 

[tx65coupe]

I think that 3 inch is a bit oversized for duals. I think that 2.5 inch exhaust is plenty. I would go with an H or X pipe and straight through mufflers like Magnaflow or Dynomax Ultraflo. If you want it louder then Magnapack or Dynomax Race Bullet. I prefer the sound of H pipe over X. The H is deeper and more mellow. The X is more raspy. I doubt it matters much which one you go with. From what I understand lower and mid RPM power is better with H and high RPM power is better with X. I have not idea if thats really the case though. I also recommend running tailpipes, dumps sound like broken exhaust and the fumes can come into the car.

 

[pypesexhaust]

It really doesn't make much difference, although I suspect the H is slightly better than the X. At least that's what the guys at Pypes told me when I asked them the same question. Mostly the X is fashionable.

What's more important is how close it is to the engine, and it's easier to get the H closer. Fuelie Corvettes actually wrapped the crosstube under the engine, it couldn't have been closer.

Just to clear any possible misinformation:

H- better low end torque + louder than no crossover
X- Better mid and High end torque + quieter than no crossover

The system in the picture is not mandrel bent therefore it flows at least 50% less efficient that a mandrel bent system like the Magnaflow or Pypes kits.

 

[2+2GT]

H- better low end torque + louder than no crossover.

The first part is quite true, an old Hot Rod dyno test showed 5-15 hp, depending on other factors, but…

The latter would be incorrect- The balance tube spreads the exhaust pulse to both mufflers, considerably mellowing the exhaust note.

 

[66forfun]

3" will give a much deeper tone and will grab some attention. It will be noisy whatever muffler you use, not bad, just loud.
I like the regular mufflers over the chambered ones.
I suggest using any type of crossover X or H.

 

[mustangbrad]

I'm doimg the 2 1/2" Magnaflow kit on my 408 W in a 70. I heard this exhaust on a similar engine and really liked the sound. 3" might not overkill, but I have heard that routing can get to be dificult.

 

[pypesexhaust]

The first part is quite true, an old Hot Rod dyno test showed 5-15 hp, depending on other factors, but…

The latter would be incorrect- The balance tube spreads the exhaust pulse to both mufflers, considerably mellowing the exhaust note.

Maybe at low RPM's, yes. However, we stand by our statement on H-pipes based on many tests we have done over the years. These sentiments are echoed from a vast majority of owners on this and other sites when the discussion of H and X pipes come up. Balance tubes transfer the 'pressure' to the unpressurized side of the exhaust. They transfer very little exhaust. Under full throttle mid and high rpms, an H balance tube no longer transfers the pressure to the unpressurized side and in fact starts to create turbulence in the exhaust system which creates a 'louder' sound. The X-pipe starts to transfer the pressure at mid rpm's and gets even better at high rpms. At high rpms, you can always hear a car with an X-pipe by it's high pitched smoother 'turbo' sound.

 

[afterglow]

Thanks for the replies everyone.

The 3" was recommended by my engine builder (fordstrokers). The headers will also be custom made.

It seems as though that H-pipes are recommended to shift the torque band down and X-pipes to shift the power band up?? On the desktop dyno peak torque is 490@4000rpm. I'm getting over 400 from 2000-5500rpm so I'm definitely biased towards the low and mid range.

 

[2+2GT]

The X-pipe starts to transfer the pressure at mid rpm's and gets even better at high rpms. At high rpms, you can always hear a car with an X-pipe by it's high pitched smoother 'turbo' sound.

I have always used actual turbo- and superchargers to get that sound.

Doesn't it mean that at the apex of the X chamber it is essentially a single exhaust at that point? That would certainly make it smoother.

 

[68RCodeConv]

3" is overkill. 2.5" is plenty even for a 500 hp motor and it will make it a LOT easier to get over the rear axle. In fact the 2.5" Flowmaster tailpipes ($100 from Summit) are mandrel bent and fit very well.

X-pipes tend to make more torque than an H and are quieter also.

 

[tx65coupe]

Those Flowmaster tail pipes don't fit worth a damn. I used them. Had it redone by an exhaust shop. That prefab stuff never fits right unless its totally vehicle specific and direct replacement like the OE style exhaust kits. Those tail pipes are for 65-70 I think.

 

[Wicked65]

3IN with X pipe and Magnaflows or Mac..


Pypes.......LOL