The whole point of a crossover pipe(X-pipe or H-pipe) is to get the out-of-balance exhaust pulse to the other bank to prevent it causing backpressure. There are 2 ways to do this...with an H(or X) pipe or do it like the GT-40 did it....by sending primaries to the opposite header:

To be fair, in the case of the GT40 it also had the effect of creating a clockwise(or counter-clockwise) swirl as each cylinder fires, which also reduces backpressure and makes more power.

Fun fact though: Only v8s benefit from a crossover pipe....v6s do not, since they do not have that "out-of-balance" cylinder, all adding a crossover pipe does for them is change the exhaust note.

 

so you could run the manifolds without a crossover but would lose out on some performance?

 

Correct

 

A crossovers isn't required.

 

My ‘66 coupe has hi-po manifolds, 2-1/4” dual pipes, and no crossover. Sounds great.

MrFreeze

 

To clarify more-- regular manifold,hipo or headers ,does not matter which. Run exhaust with or without H/x pipe.

 

I actually like the sound of divorced true duals the best. And no you don't have to have an H pipe but it is better to have one no matter what manifolds or headers you have. I do have an H pipe on my car. Early GT350s, AC Cobras, Corvettes and old hot rods don't have H or X pipes etc Millions of factory single exhaust cars were converted to dual exhaust back in the day and most didn't have a crossover pipe.
800 × 600

 

I use an H pipe with headers.

 

Went to a X pipe on my latest exhaust. I really like it.

 

I made my h pipe 2.250"

 

You don't NEED one but it's there for a reason. Remember, Henry didn't spend any extra when it wasn't needed.

In the illustration below, the firing order is shown outside the diagram in bold black numbers. The green line with an arrow indicates that when that cylinder is on the exhaust stroke, pushing expanding spent gases into the exhaust system, the cylinder it's pointing at is at TDC ending the exhaust stroke and entering the intake stroke (the "overlap" portion when both intake and exhaust valves may be open and "reversion" in play. Reversion is when the airflow wants to go in the opposite direction of normal due to pressure changes. The crossover is designed to "balance" the reversion effect to help the exhaust gases efficiently escape.

 

Searching for dyno testing of crossover, I only see people reporting on sound. Does anyone have link showing actual HP/TQ gains?

I plan to install one to tone down the noise but I'm a little skeptical that they do anything for HP/TQ unless you have long tube headers and the crossover is placed right at the collector.

 

2.5K views · 61 reactions | Straight Exhaust vs H-Pipe vs X-Pipe! - Engine Masters Ep. 22 The stock 5.3L GM LS3 engine in the video used the "go to gold sauce", as David describes it, Signature Series 5w30: http://canadianoil.wboil.com/storefront/asl.html | Premium Oil Inc

Straight Exhaust vs H-Pipe vs X-Pipe! - Engine Masters Ep. 22 The stock 5.3L GM LS3 engine in the video used the "go to gold sauce", as David describes it, Signature Series 5w30:...

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X and H are identical on power. Both make more than none.

 

The H pipe will also on getting rid of that drone that some exhaust systems have.

 

Another aspect is that it makes the exhaust system sturdier. With two single pipes, it's quite a distance between the manifold and the hanger at the end of the floor pan. Wiggling around this long pipe due to vibrations could cause issues with exhaust sealing. That's actually something OEMs care more about that gaining a horsepower or two, especially if it also reduces noise.

It's a detail that has some benefit. Nothing spectacular but worth it.

But to answer the OP's question: I think what people meant when saying that you need an H pipe with Hipo manifolds is that you need a Hipo specific H pipe. The one for regular manifolds doesn't fit due to the different exits.

 

Crossovers are a tuning tool. Typically, they make about 1 to 1.5% more power than true straight pipe dual exhaust. That means if your car makes about 150 horsepower to the rear tires (stock 289 2V engine), you will gain a whopping 1-2 horsepower. Even on a very powerful engine, you are not going to notice any change in acceleration between "with" or "without".

It does, however, change the exhaust note. In my experience, it did not 'quiet things down'. It just changes the tone a little. A true dual setup has a very distinct burble, and when you stand behind the car, you can really hear the 'back and forth' between both pipes. At highway speeds, it has more of a ragged note, tending towards drone (depending on your muffler setup).

An H pipe preserves a lot of the character of a true dual system, yet smoothing the tone and causing less drone at highway speeds. It's the classic 'musclecar' sound.

X pipe smooths the burble effect even more, creating more of a modern exhaust sound. It is more reminiscent of a tuned exhaust; almost like an Indy car, though of course not high pitched. Just smoother than the duals or H-pipe setups.

 

Also the crossover of the H needs to be a smaller pipe. I believe it is a percentage of the pipe diameter and i have always seen them behind the transmission mount not at the headers

 

Just got the ‘56 f100 back from getting custom exhaust from my neighbors shop, I was amazed he was able to put a cross over pipe on it sounds great with the cherry bombs, just don’t ask the neighbors lol

 

I assume the reason most people run h-pipes with hipo manifolds is because then you can just buy premade repo exhaust parts and bolt them on.

 

you can run duals without an H pipe but why would you?

 

First time I've ever heard that.

 

Someone here said that you need a hipo specific h pipe if you were doing one. and that made more sense when I read that.

 

there is a A code gt dual H pipe
there is also a K code dual exhaust H pipe
each fits a different set of exhaust manifolds.

 

My 69 Cougar H code has straight pipes with cherry bombs and sounds very good. It's really not obnoxiously loud. I bought it that way and since I'm not looking for extra bit of power it's not likely that I'll ever change it.

Since the Mustang that I'm doing doesn't have an exhaust system yet, I'll probably go ahead and put on in.

 

How can it be straight pipes if it has glasspacks? Bet it sounds good though.

 

I would like to have an "X" crossover pipe in my '67 but with me tucking my exhaust into the tunnel above the x-brace there was no room to put one towards the bellhousing. I might could have fitted an H crossover but figured things were complex enough under there already and it just wasn't worth it.