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H-Pipe Installation

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My 454" powered '71 had 2-1/2" dual exhaust and home made "performance" mufflers. Last summer I installed an h-pipe to see if it would quiet the exhaust noise down and maybe provide a little gain in power. Knowing an h-pipe had to be as close to the engine as possible to provide any meaningful gain in power I installed mine right under my torque converter. I used my AutoCad program to design it with a 3/4' drop so it would clear the bottom of my torque converter and used stainless steel "band" clamps to seal it. It did quiet the exhaust noise down maybe 10% as both of the mufflers now share every exhaust pulse. My starter makes a lot more noise with the dust cover removed but it's not enough to annoy me.
 

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dougelam

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2002 Roadster
My 454" powered '71 had 2-1/2" dual exhaust and home made "performance" mufflers. Last summer I installed an h-pipe to see if it would quiet the exhaust noise down and maybe provide a little gain in power. Knowing an h-pipe had to be as close to the engine as possible to provide any meaningful gain in power I installed mine right under my torque converter. I used my AutoCad program to design it with a 3/4' drop so it would clear the bottom of my torque converter and used stainless steel "band" clamps to seal it. It did quiet the exhaust noise down maybe 10% as both of the mufflers now share every exhaust pulse. My starter makes a lot more noise with the dust cover removed but it's not enough to annoy me.
Well there be any power gain when mufflers are used?

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Antz81

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Is this a new H pipe? Or is this the same one you have already showed us?
Either way, why have you used claps to seal it rather that a welded joint or a flange?
 
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Is this a new H pipe? Or is this the same one you have already showed us?
Either way, why have you used claps to seal it rather that a welded joint or a flange?


If I had already showed it to you I simply forgot. I chose band clamps to attach/seal it because that was the easiest method of removing it for those few times when I need to drop the pipes. Around noon I'm going to drop my spare tire carrier and take a couple of pictures of my $5.50 True Value gas shut off valves that I installed on my '68 and '71. It's awfully handy to be able to shut the flow of gas off from a tank and my pictures will show you how easy it is to install one.
 

LLC5

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If I had already showed it to you I simply forgot. I chose band clamps to attach/seal it because that was the easiest method of removing it for those few times when I need to drop the pipes. Around noon I'm going to drop my spare tire carrier and take a couple of pictures of my $5.50 True Value gas shut off valves that I installed on my '68 and '71. It's awfully handy to be able to shut the flow of gas off from a tank and my pictures will show you how easy it is to install one.



Great.

You can title it: "How to create another fuel leak source in your C3". And I am sure yours will........

Brilliant.
 

kpic

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Columbus, NC/NE Georgia
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1997 boosted silver coupe
Great.

You can title it: "How to create another fuel leak source in your C3". And I am sure yours will........

Brilliant.

Perhaps modifying his "With These C3's It NEVER Stops" to "With my C3 It NEVER Stops" redux would be a fitting title?
 
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Well there be any power gain when mufflers are used?

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Yes, there is a gain in power because of the fact American V8's use 90 degree crankshafts and not flat crankshafts like the Ferrari V8's that space the firing impulses left bank right bank left bank right bank and so on. The H-pipe bleeds some of the exhaust gas pressure off and send it to the other pipe. That's why the American manufacturers began using H or X pipes a long time ago.
 
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American V8's

The American V8's have an uneven firing sequence like this: Left Right Right Left Right Left Left Right so they need an H or Y pipe to help even out the exhaust pulses to the mufflers.

The Ferrari V8's have a firing sequence like this: Left Right Left Right Left Right Left Right so the exhaust pulses reach the left muffler 180 degrees apart and the right muffler 180 degrees apart. That's why the Ferrari exhaust sounds so smooth.

So an H or Y pipe makes the exhaust note more "even" sounding and they do allow a small power gain at the higher rpm's when things get uh "busy". Google "Ferrari V8 Crankshaft" to see a picture of their "flat" crankshaft with rod journals spaced 180 degrees apart. The disadvantage of flat crankshafts is they have to be fully counter-weighted which makes them heavier. You can buy flat crankshafts for Chevrolets but they also need camshafts that are specially ground for 180 degree flat crankshafts and their different firing order.

By installing an H pipe on my '71 I'm allowing BOTH of my mufflers to share every exhaust pulse which makes the sound a little bit quieter.
 

dougelam

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2002 Roadster
The American V8's have an uneven firing sequence like this: Left Right Right Left Right Left Left Right so they need an H or Y pipe to help even out the exhaust pulses to the mufflers.

The Ferrari V8's have a firing sequence like this: Left Right Left Right Left Right Left Right so the exhaust pulses reach the left muffler 180 degrees apart and the right muffler 180 degrees apart. That's why the Ferrari exhaust sounds so smooth.

So an H or Y pipe makes the exhaust note more "even" sounding and they do allow a small power gain at the higher rpm's when things get uh "busy". Google "Ferrari V8 Crankshaft" to see a picture of their "flat" crankshaft with rod journals spaced 180 degrees apart. The disadvantage of flat crankshafts is they have to be fully counter-weighted which makes them heavier. You can buy flat crankshafts for Chevrolets but they also need camshafts that are specially ground for 180 degree flat crankshafts and their different firing order.

By installing an H pipe on my '71 I'm allowing BOTH of my mufflers to share every exhaust pulse which makes the sound a little bit quieter.
That didn't explained the power gain

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navy2kcoupe

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West Central FL and SE Mass.
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The disadvantage of flat crankshafts is they have to be fully counter-weighted which makes them heavier.

I don't believe that to be true. I believe the counterweights are on the cross-plane crankshaft, making them heavier and prone to a longer time
to rev than a flat-plane crankshaft, but I'm not an engineer and don't know much........

Andy :w
 
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Please Accept My Apology

I don't believe that to be true. I believe the counterweights are on the cross-plane crankshaft, making them heavier and prone to a longer time
to rev than a flat-plane crankshaft, but I'm not an engineer and don't know much........

Andy :w


You are 100% right and I am 100% wrong. The last time I studied flat plane crankshafts was a long time ago and time has dulled my memory. Thank you for waking me up and please accept my apology.

Now back to the reason why an H pipe allows a small power gain. At a high rpm the exhaust pulses of cylinders firing only 90 degrees apart puts a slug of pressure in the pipe and by bleeding some of that pressure off a small gain in power is realized. I have seen many C3 owners put H or X pipes back at or behind the rear axle and that only quiets the exhaust some. For a gain in power the H or X pipe must be as close to the engine as possible and that's why I chose to put mine under my torque converter even though it would allow more starter noise to escape.
 

dougelam

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Messages
453
Location
Michigan
Corvette
2002 Roadster
Yes, there is a gain in power because of the fact American V8's use 90 degree crankshafts and not flat crankshafts like the Ferrari V8's that space the firing impulses left bank right bank left bank right bank and so on. The H-pipe bleeds some of the exhaust gas pressure off and send it to the other pipe. That's why the American manufacturers began using H or X pipes a long time ago.
So you get a power gain from an H pipe but not headers?

Imagine that!

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H Pipe

If you look real closely you can see a skid plate that is welded to my H pipe to protect the front edge of my deeper transmission oil pan. As the last mile of dirt road leading to my house is bulldozer cut there are many rocks jutting out of the surface of the road which had damaged my deeper pan. And headers? As OPEN headers are intended to bypass the restrictions of the exhaust pipes, mufflers, and tail pipes they don't provide any gain when blowing thru the very restrictions they are intended to bypass. In the last 50 years people have forgotten headers have to be run OPEN to do what they are intended to do.
 

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