Bad ass pipes

Herb Becker made these pipes for Andy Cox's unstreamlined land speed racer (149mph so far).

"...start out at 1 5/8", then steps to 1 3/4", then 1 7/8", then finishes at 2", with reverse cones. We were pretty happy with the results; ... 94rwhp.

I saw a guy at the Broadford Bonanza about 3 years ago with a commando with pipes like that. With a commando motor, it is big enough to still have power if it drops off the megaphone on a road race circuit. But I would not like it. For a land speed record, it is probably OK if you stagger off at the beginning and get a big kick in the pants as the motor comes on song.

I bet that sounds great. Any movies anywhere?

I'm loving those pipes

You might be able to hear them at Bonneville this year.

I have some Short vids from the Dino runs. I’ll try to get them posted.

When I was road-racing regularly, the best time at any race meeting was when I was driving home down the highway in my car, without that racket banging in my ears.

I've got a brief visit to Bonneville planned for the bike speed week, probably the most boring ride ever coming up from Houston area. I'm only going to stay a day or two, just wanted to hit an item on my bucket list. I'd love to see and hear a Norton run there.

jseng1 said:

You might be able to hear them at Bonneville this year.

Click to expand...

From the looks of them I probably will hear them at Bonneville and I live not far from Herb in Ontario

Hopefully you don't live near any place named Jericho

https://en.wikipedia.org/wiki/Battle_of_Jericho#/media/File:JSC_the_battle_of_Jericho.png

My bike has a 2 into 1 pipe with muffler and it is TOO LOUD but performs extremely well. The 850 cam is advanced 12 degrees ahead of standard to compensate for the pipe.

Chatting with someone recently who gave some sage advice on the stepped header, particularly with a two-into-one arrangement. I don't understand the phenomena of stepped headers but the simulation he ran was encouraging.

Dances

stepped headers are/were often used as an alternative to a fully tapered exhaust. Much easier to assemble, and very similar results, although for optimum performance the full taper is to be preferred.
How many pipe manufacturers are willing to roll and bend tapered headers these days ?
Skilled sheet metal workers capable of this work do exist, the difficulty is finding one.

Yes, I missed the point of explaining the distinction between stepped headers and true taper.

I recall Gordon Blair pointing out the step between the bell mouth and bore of the Mikunis on the 500cc twin we were campaigning at the time and saying something along the lines of “confusing” the intake signal. Probably a similar situation on the exhaust.

So the question has been cast out there and stands.

Snotzo said:

Skilled sheet metal workers capable of this work do exist, the difficulty is finding one.

Click to expand...

Anyone care to chime in?

There could be something to the edges of the steps helping to prevent reversion of gas flow.

I believe it has to do with discrete signals and when they are reporting back to the valve.

Well, I've got pics of the finished pipes on the bike at the dragstrip, a vid of the 95hp dyno run and a pic of the actual dyno sheet, but I can't figure out how to (easily, with copy and paste of URLs) post the pics here from my google photos. Most of my stuff is on IG and FB, so if anyone want to see regular updates, follow my Instgram: @santaschoyce, or my Facebook: Andy Cox, Waterloo ON.

You can theorise about the effect of steps in the inlet and exhaust tracts, however it is what works which is important. There have been claims that BSA Gold Stars perform better if there is a step in the inlet tract, however the comparisons might have been done while jetting was being changed. Cause and effect can be deceiving. My 2 into1 exhaust is made up of pieces of tube welded together, so there must be welding flash on the interior at the joins. To my mind, the diameter of the pipe is of more importance. Early Triumphs had fat pipes and so did Manxes. My friend was an A grader with the fastest Manx in Victoria. I was once in his workshop and commented on the skinny exhaust on his Manx. He said ' you notice too much'. I've read magazine articles which claim the fatter pipe is better on Manxes, but my friend was the only A grader who ever got close to Ron Toombs on the Henderson Matchless which had a highly developed 4-valve motor.
I would not use fat pipes on a road race bike, because of the effect on mid-range and bottom end power. But on a land speed bike, they might be good - once you are near top speed. Dyno figures might be important to some people, but what happens in practice might not be what you might expect.
.

Thanks, Jim. Best wishes for Bonneville.

By the way, that place is magical. More than mere bucket list.
Can't be described.

Our Boyer EI causes a lot of grief with the Dyno software when the dyno rpm sensor is hooked onto the coil, so there are no rpm readings on the chart, but we logged rpm from our WEGO III sensor. Peak HP was just past 7500rpm.