Recently I have been kicking an idea around that I wanted to have a H-Pipe fitted to my twin exhaust system. This would be a trade-off, noise vs power the pros and cons.
By adding an H-pipe section it increases power. Even when headers are installed, the close firing cylinders are competing for space in the exhaust pipe after the collector, which creates back pressure and reduces power. Connecting the exhaust pipes allows pressure to escape to the other side of the system, with a resulting gain in low-end and mid-range torque. However, the effectiveness of an H-pipe section decreases somewhat at higher rpm. The increased exhaust gas velocity at high rpm causes most of the exhaust to take the path of least resistance and continue down the exhaust pipe, rather than make the turn into the H-pipe.
On the other hand, when the two close firing cylinders are exhausting on one bank, there is nothing happening in the other bank, so connecting both pipes effectively enlarged the exhaust system, allowing these exhaust pulses to exit through both sides of the system. It was found that, with the addition of an H-pipe, exhaust noise could be reduced by as much as two decibels.
So I took the plunge and made a date at Mustang Maniac for my car to go down and have the H-Pipe fitted. It was good to see Yogi again and he had already cleared a ramp for me to drive straight onto. Within a minute or so he had already pre-cut a length of pipe ready, quite impressive really, and would need proper fitting & fettling.
The pipe was offered up and the best position worked out for it. There isn’t a lot of space under there due to the headers of my exhaust, not to mention the custom-made brake lever as a result of the exhaust headers. Yogi marked up the proposed fitting points on the first of the exhaust pipes and made the initial holes. The holes were made bigger a little at a time in order fir the diameter of the pipes.
The surrounding area was sanded down ready for a little tack weld. The pipe was offered up numerous times to get the fitting and location correct. The welder was set up for the task, making sure the weld would be just how Yogi wanted it.
With the tacks in place a final check for clearance and position then the welding could start. Hand held face mask for more tack welds then the full on mask for the proper welding. I just love the blue arch light from the welding.
To complete the top of the pipes the rest of the exhaust would have to be taken down and finish the seam weld.
The H-Pipe finished and all tightened back up into place. The H-Pipe has a curve in order to make it fit within the space, a straight pipe simply wouldn’t fit. This is where the skill of the guys at Mustang Maniac can work around and make something to fit properly. Something that many other competitors try to do and fail big time.
I couldn’t wait to get in the car so I could start her up almost jumping in the car before it had got down on the ground. The exhaust is now a slightly deeper tone and a more even note. Although the volume is still there I’m glad to say. The drive home I could feel the difference at lower acceleration using the torque and not revs and got up to speed a little faster, it has improved the power band range no question about it.
Thanks Yogi for the good work.
I was then left to my own devises under the car to clean it while it was back up in the air on the ramps again. Yes I did, and I do clean the underside of the car. Then I noticed a split on the steering ram rubber boot. I picked up a repair kit from the new shop of Mustang Maniac’s and took it home ready to swap it over.
I have made a complete walk-through of the full process here, in more detail, or simply copy the link to the browser. This explanation below is just a quick summary of what I done.
The repair kit from Mustang Maniac was a very reasonable £24 and straight of the shelf with everything you need in it. Click here for the link to buy it if you need one.
The boot had ripped completely and looks more like it has torn or been caught to damage it so much. I suspect driving over fields and rough tracks to get to the Car Shows has done the damage as this part does sit lower than normal Mustangs.
So the process; there are just two nuts that holds the ram in place, one for the tension and the other for locking in place. My mounting bracket is a modified bracket to sit lower down from the chassis because of the larger exhaust headers and not having enough clearance for the steering ram. However, the principles are exactly the same regardless of the bracket being standard or the lowered upgrade. Undo the bolts and slide off the outer steel plate.
The bushing can either be pulled of or just push the ram through and out the other side. On the ram itself there will be a sleeve that sits inside the bushings inside the bracket.
The bushings will probably be stuck to the bracket and may need a little persuasion to get them off, I used a mini hook that makes it much easier to remove without slipping and mashing your knuckles.
Behind the bracket on the inner side there is a pinch clip or single ear O ring that also needs to come off. This can be a pair of cutters, pliers or what ever, again I just hooked it off. be careful not to damage the ram shaft. With the pinch clip off, remove the damaged boot and clean the shaft.
The next part is to refit the boot and the new pinch clip, If you don’t have a pinch clip tool you can use an alternative fixing. Slide the new boot over the cleaned shaft with the bigger end first, this has to sit over the end of the cylinder ram’s mounting flange.
As my bracket is thicker than the standard bracket, this little modification is not required for the normal bracket. I had to trim a little off (about a third) the bushings otherwise I would not be able to fit the nuts back onto the end of the ram to tighten it back up.
Don’t bother to fit the cylinder end of the boot just yet. Next refit the outer plate and bushing on the inner side of the bracket, they do need to be fitted the correct way, so take care when refitting..
Slide the ram shaft sleeve on and will fit inside the bushing about a quarter of the way. Make sure enough is exposed in order to fit into the other bushing once it is through the bracket.
Push the shaft through the bracket and locate the lip of the bushing into the bracket hole, You should be able to see the end of the shaft and the sleeve ready to be surrounded by the next bushing and then the outer plate.
Looking on from the side. the bracket is sandwiched by bushings and then a plate on each side of the bushings. Slide a nut onto the shaft to tighten in place, then the locking nut.
Now we can secure the bracket end of the boot with the pinch clip tool. Use the proper tool to clamp the bracket in place and not pliers to squash it in place. Be careful not to damage or rip the boot with the tool.
At the other cylinder end you can now stretch it over the lip of the flange. Make sure that the boot is not twisted and is able to move freely.
With the boot in place I found that it can pop of the cylinder and is a pain. So most people use a cable tie just to hold it in place from slipping off. Trim the excess tie and make sure the boot is still free to move.
That’s it job done, total of no more than an hour including me taking the pictures!
My car was due for its MOT later this month, even though it technically it doesn’t need one. However most like-minded and conscientious classic car owners, they want to know that their car is safe and not going to cause problems. This split rubber boot would have been a failure of that test. Once the boot was changed, I took the car to the MOT centre where she then passed with flying colours. Now I’m ready for the car shows again.
I usually look over the car when I clean it to see if anything out of the ordinary is wrong. This was one of those times that saved me not being allowed to drive the car as a result of the failure. It’s a good idea to check the old cars over especially if they have been stored up for a while. Mine had sat in the garage unmoved since the end of October last year.
11 thoughts on “Power vs Noise”
This might be a dumb question, but does an “H” pipe function similarly to an “X” pipe? The newer high performance cars seem to use the X pipes.
In effect yes they’re the same, the x pipe just allows a more streamlined flow of exhaust from each side of the engine. Where as the H style sort of has a little more turbulence to go across each side of the exhaust bridge if you like.
I ran my exhaust without the H for a couple of years, I had a nice uneven idle which I liked.
The H or X is supposed to give a bit more performance. When I retro fitted my H pipe the engine idle was smoother and more even.
Thanks for the clarification. I. Glad you like the new results.
Nice article, and especially nice photographs. Well done!
Thanks Richard. 👍
Another great article with great pics and descriptions. It’s also nice to see that you accounted for some occasions that you have to make adjustments for added / upgraded parts. Welcome to the wide wide world of hot rods! Once again, well done gentleman!
Thanks Bob. I appreciate the kind comments. I wanted power from long headers, the downside is everything then becomes non standard as it were. But these things can be overcome, trouble is there is not much information on the variables, I hope it helps somebody some day. 👍
Very detailed and informative article. It now has me thinking about how my car can benefit from an H pipe.
Thanks, I collated some of that information from a few websites that know far more than me, they all pretty much said the same thing. It was a chance read that made me think of getting the H-pipes in the first place too. 👍
It’s always a good idea to check over the car at any time. Good to see the little lady down here again. 👍👍
Thanks for fitting me in at short notice. 👍😃