new Headers and H-pipe installed

[Evolution1980]

Then: Hooker Competition headers (flat black) and straight back exhaust (2.25" tubing)

Now: Hooker Super Competition headers (ceramic coated), H-pipe, and straight back exhaust (2.25" tubing)

-------------
First off, the ceramic coated sure are purdy compared to the old, surface rusted black ones!! (With that out of the way now...)

Differences in headers: Super Comps have slightly larger primary tubes (+1/8" maybe?) and use 18 guage steel versus 16 gauge on the regular Comps. The Super Comps are lighter. The primary tubes are routed differently; they have less angular bends to allow for better flow and thus they don't hug the block as much as the regular Comps did. And lastly, the collectors are about 1-1.5" longer on the Super Comps, so a direct, bolt-in replacement wasn't possible.

Being that I was now going to have to modify the exhaust, my mechanic decided he was going to put in the H-pipe. I was leaning towards X, but...oh well. The H-pipe setup was only $32 versus $100 or more for the X-pipe setup.

Right off the bat, the low end torque increase seemed noticeable. This was somewhat of a surprise as the larger primary tubes on the headers should've reduced the bottom-end torque while increasing upper-end HP. I'm guessing the addition of the H-pipe made up for that loss of torque from larger primary tubes.

The sound hasn't changed too much. The noticeable sound difference comes in the upper RPM ranges (3500+). If you heard my car before, you'd know that at 3500 RPM and higher it had a distinctive POP-POP-POP-POP-POP sound. The sound is now much more constant throughout the entire RPM range. "Smoother" is how I would explain it. More refined. No more POP-POP. It almost gets rid of that carburator sound altogher and changes it to a EFI sound...almost.

What surprised me overall was that typically, in my opinion, the louder the car is, the greater the "sensation" of acceleration or speed. If the actual performance gains were minimal at best, it would have seemed even more minimal due to less sound overall. I expected the quieter exhaust note to decrease the sensation. But even with the smoother tone, the car surprisingly feels much more responsive. Either way, I'll know for sure as I have an appointment with the dynojet on May 14th. It won't be an exact "before and after" since my last dyno run because I've had my carb tweeked some more, but carb tweeks shouldn't make as big a difference as the change in exhaust. We'll see!
I'll post some pics of the exhaust before and after in a few days...maybe tonight even. I'll also update this thread with my Dyno results when I get 'em.

I think I'll sometime miss the rap of the old exhaust setup, but I was getting slightly tired of it anyways. Change is good. And if it brings more performance, that's even more good-er-er!

 

[waterboy1976]

Heya Evo......Who does your exhaust work? You? I need to change out my Flowmaster 40s for 50s and put an H pipe in...

 

[Evolution1980]

Heya Evo......Who does your exhaust work? You? I need to change out my Flowmaster 40s for 50s and put an H pipe in...

My own personal mechanic...for the past 11 years! He's pretty much built my car into what it is today. Hell, it's as much his car as it is mine! :L If you need work done, let me know. He only works on personal references from people he likes.

 

[bossvette]

My own personal mechanic.

is that any thing like "personal trainer"

 

[Evolution1980]

is that any thing like "personal trainer"

Well, kinda, but not really. What I mean is that he's the only one besides myself allowed to turn a wrench on my car.

 

[leeboy66]

Evo, how much did those super comps run you? What are the benefits of an H-pipe? Why is an H-pipe or an X-pipe better than a straight back dual exhaust? I am very interested in replacing my stock exhaust.

 

[Evolution1980]

Evo, how much did those super comps run you? What are the benefits of an H-pipe? Why is an H-pipe or an X-pipe better than a straight back dual exhaust? I am very interested in replacing my stock exhaust.

I'll get back to you later on the differences, as I am in the middle of some other stuff right now.

Super Comps (Ceramic coated) - $589.88
Premium Gaskets - $16.88
Stage 8 Locking Header bolts - $39.95
H-Pipe kit - $29.95

I could've passed on the premium gasket and Stage 8 bolts, as the headers came with gaskets and bolts, but I consider the better gaskets and especially the Stage 8 bolts a necessity.

If you are just looking for headers, I'll be selling my regular Hooker Comps on eBay, probably after CruiseFest when I have some time to do all that stuff.

 

[waterboy1976]

I love my Super Comp Ceramics.....

 

[Evolution1980]

Why is an H-pipe or an X-pipe better than a straight back dual exhaust?

The text below is taken from this link.

How And Why "X"-Pipes Work
By Bruce Wayne, MagnaFlow Performance

There has been an enormous amount of press about getting more out of performance exhaust systems. By incorporating "cross-over" or "X"- pipes in dual pipe systems, to balance out flow, many enthusiasts have found an extra edge. However, the perception is that this is new technology. Nothing could be further from the truth. But, why is an "X" pipe better than an "H"?

The reason an X-Pipe crossover works better than an H-pipe crossover isn't more flow because of volume, but more effective use of exhaust gas velocity. Exhaust gas (or air) has surface tension, and flows much like liquid would through the same pipe system. As the cylinders of each bank on a "V" style motor fire, they create a pulse in the system. The pulses will alternate back and forth from bank to bank as the motor runs. With multiple cylinders, such as a V-8, the eight cylinders alternately fire creates lots of pulses in the system.

If you put your hand behind the tailpipe, it would feel like a constant flow of air, but what it really is a lot of singular pulses giving the impression of constant flow. The idea behind the H and X style crossover is to unite the two banks of cylinders for better exhaust gas scavenging. Instead of two separate banks of four cylinders doing their own work, the crossover uses the pulse created by a firing cylinder of one bank to create a vacuum in the other bank because of surface tension. When a cylinder of the other bank is ready to fire, instead of the piston having to force the exhaust gas out of the cylinder, the vacuum that was created by the other cylinder bank helps suck the exhaust gas out of the cylinder, hence the term "scavenging."


Whenever you can reduce the load on an internal combustion engine, you are likely going to see performance and efficiency benefits. The difference between an H and X crossover is a smoother path for the exhaust gas to follow. Exhaust gas, like a liquid, will follow a path with the least amount of resistance. An H crossover has a path with two sharp 90-degree angles that are close together. An X crossover has a path with a much more gradual bend to allow the exhaust gases to continue their path back out to the ends of the tailpipes, rather then turning sideways for a short distance, then turn again to head out the tailpipes. Smooth flow with high velocity means more power by use of scavenging. Using an exhaust system with too large of piping diameter work against scavenging in the same way that running an exhaust with too small of tubing chokes the motor and forces it to work harder to expel the exhaust gases.
<end of article>
---------------------------

Now, obviously I'm not in the exhaust engineering business, but my only question to his "logic" is that he talks of exhaust, like liquid, taking the path of least resistence. But then goes on to say that the exhaust would need to make a 90° bend at an H-pipe versus a smoother flow through an X-pipe. Well, if exhaust takes the path of least resistence, it's not going to go 90° into the "H". It's going to continue on straight in it's path. The only thing the H-pipe (or "balance tube") does is balance out the exhaust pulses and aid in the exhaust scavenging effect. In hunting down this article, I ran across a Chevelle forum and many of the members there were saying that they didn't like the sound of the X-pipe as it gave a high-pitch sound at higher RPM's. (For whatever that's worth).

Until I get to the Dyno on the 14th, I won't know the exact performance numbers. In the article above (from the link), the author talks of getting 15.8HP and 11.8Tq over the base setup. If the H-pipe setup gains anywhere near that, then I think it's money better spent on the H. $32 versus $100+...??? And then there's the sound difference (as perceived by others, not myself, in reference to X -vs- H.)

 

[leeboy66]

Thanks, Evo for your detailed response. As usual you have enlightened me greatly. Let me know how much you want for your old headers. I may be interested.

 

[Evolution1980]

Thanks, Evo for your detailed response. As usual you have enlightened me greatly. Let me know how much you want for your old headers. I may be interested.

I'll get back to ya after CruiseFest if yer still interested. Right now, they are just going back in the box that the new ones came in.

 

[82ColEd]

Thanks for doing all the writing Andre.. Really interesting stuff.. I always wondered about X vs. H piping.. I understand the concept of scavanging, but i'd be interesting to see the real world difference, ie. your dyno.. You didnt have any crossover pipe in it before, right ?


-Stefan

 

[Evolution1980]

You didnt have any crossover pipe in it before, right?

Correct. It was from the headers straight back...well, I mean, the usual bends underneath the car, but yeah, one single pipe front-to-back for each side.

 

[82ColEd]

I was thinking H pipe on the drive home: My thought is that the exhaust passing by the "-" in the H forces the air/exhaust from the other side to stream through the "-", thus creating a vacuum (small maybe). I cant see it going through 2 90 degree angles either, but the above should work.. I think...

 

[Evolution1980]

BEFORE PICS

Here are the after pics (Obviously!). I have taken a couple shots of each because in some of the pics, it's easy to misinterpret the spacing between things. Although, the driver header IS pretty much touching the steering u-joints.

​

Note it lines up evenly with the transmission crossmember, but when it gets back to the rear crossmember, it's favored to the passenger side by about 3". This almost has it touching the leaf spring when in [P] or [N]. However, once the car is in gear, the leaf spring compresses thus opening up that gap a little more.
​

 

[82ColEd]

Purdy Andre.. :cool

Not much room there (either between the linkage or underneath).. :crazy

 

[Tepot]

Wow. really nice job !!. I really like your new headers. I'm gonna have to get a pair of those for christmas.

 

[Evolution1980]

Wow. really nice job !!. I really like your new headers. I'm gonna have to get a pair of those for christmas.

Per your other thread, they'll definitely help continue to improve the appearance of things under the hood.

 

[Bob Chadwick]

Looking good Andre.

 

[G Winter]

what about the C4

What about the exhaust system on a C4 ? I has a balance of sorts with the center cat. I think the lead pipes are 2 1/4 ? the cat is 3 in. If you gut the cat is the effect the same as a crossover? I am considering redoing my exhaust on my 90 to free up the flow just a little. I hope I can get this done without losing low end torque. I really like what it has for everyday driving.

Glenn