"Big Bore" head pipes and mufflers

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The MotorTune fella uses JBWeld, even on the intake side as well as exht. He says heat makes it pliable to still adhere with the thermal expansion.
On Exhat side, failure just blows right out on road but then the porting is ruined.
I've used JBW to replace a finger size cast iron barrel fin and it worked and stayed put, BUT it got malleable soft at running temps, which was ok as helped to mold it back even if I bumped it farting around forgetting the weak spot. I ran it on Peel then put on Trixie fine Until crap foil over paper head gasket blew out at oil hole and gas jetted the fake fin off and almost thru fuel hose too.

From a head porting site.
A-788 Splash Zone or Kop-Koat which ever name you prefer, is the ONLY epoxy I have ever seen that will stand up to the rigors of racing. If you use it with Alcohol you have to seal it with a clear coat paint in order to seal it off. You can use clear Acrylic or Emron clear coat. After you shape the epoxy to what you want, wash the head, dry it and clean it with Acetone. Then heat it up to 150 degrees and apply the Acrylic clear coat over the top of it and make sure to get the edges. Don't be shy with the stuff. Let it dry for 12 to 24 hours.
All epoxies will break down with Alcohol. Its just to corrosive. This procedure will make it last ten time longer.
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Click to expand...

I asked the Chief of British Toys Michael Starkey who has done a couple of Combat head for me and many other for others. > What kind would work in shaping exht track in air cooled hot BI motor?<

http://www.devcon.com/devconcatsolution.cfm?catid=34
ask their "tech department"..they are VERY knowledgeable

http://www.caswellplating.com/permatex/ ... prods.html
product 26346 (ceramic 2000*F one part)

http://www.por15.com/product.asp?productid=7
(download the pdf instructions)

the problem is the vast "movement" of the metal (coefficient of expansion
and contraction) during heat cycles as always, the *correct repair* is WELD (TIG back-gassed) and re-machine..positive, permanent, secure...keep in mind you do *NOT* want to "localize" HUGE AMOUNTS OF HEAT in the weld process (which will DISTORT the head!)... I did a Combat head that had been "exhaust thread repaired" by someone who "threw a truckload of heat" at the head and surely fixed the exhaust *BUT* tweaked the head enuff that the guides were "under stress" and it took THREE borings of the new guides to get them "reamed to proper fit"...
Click to expand...
 
I copied this from the brit-iron list some time ago -

Date: Thu, 15 Jun 2006 22:47:52 -0700
From: Ken Canaga <kcanaga@ADELPHIA.NET>
Subject: Re: Exhaust pipe diameter and performance, tuning

Back in the early 7s, the Norton race shop did extensive dyno testing of
race exhaust systems for Commando engines. The factory notes listed details
of systems using 1 1/2", 1 3/8", and 1 5/8" pipes. If I recall correctly,
all were 2 into 2 systems with racing reverse cone megaphones. The
divergence angles and outlet diameter for the megs were different for the
various pipe sizes. They looked at both top end performance and mid-range,
but also sound level, which was an issue for some venues/clubs/classes.
They tried a short (3 1/2") perforated core silencer in place of the
reverse cone, which was good for sound level (107 dB), but gave it up
because it hurt power too much. Best top end power was with the 1 5/8"
pipes (30" - 31" length). They were able to get excellent top end power and
still just barely meet the ACU sound requirement of 115 dB with several
different reverse cone megs. One of the favorites for the 750 was with a
24" megaphone, diverging to 3 3/8" o.d., with a short reverse cone with a 2
1/2" opening. It gave good horsepower from 4200 rpm up, but lacked torque
coming out of tight corners. For the 850 they had a system with the same
pipes, but a 20" mega with 3 1/2" o.d., and a 3 1/2" long reverse cone with
a 2" diameter outlet. It made good power from 4000 rpm up. They had
another system with 1 5/8" pipes 30" long, and a longer (28") mega with a 3
1/4" o.d., and again the 3 1/2" long reverse cone with 2 " outlet. It gave
more power at top end, but tended to be hard on crankshaft and crankcase
reliability (I'm guessing that's because they revved higher). They tried a
Dunstall exhaust, with 1 5/8" pipes 28" - 30" long, and 24" mega with a 3"
outlet and no reverse cone. It provided a good spread of power, but was too
loud. They sometimes used a system with 1 3/8" pipes (stock Commando size)
35" long, with a 20" mega diverging to 3 1/2" o.d., topped by a 3 1/4" long
reverse cone with a 2" outlet. It gave good power in a 750 from 3800 rpm,
but was not as good on top end. This might be the exhaust they used on some
of the production racers the factory raced, with both megas on the right
hand side, but I'm not positive of that. One of the things they demonstrated, was that the Commando, at least as tuned by the race shop, was
not too sensitive to the exhaust. As long as the dimensions were in the
right ballpark, there were several combinations that would work pretty well.

On a more personal note, back in the day I tried a variety of exhaust
systems on my race bikes, and settled on one recommended by Axtell. I used
1 5/8" pipes 28" - 29" long, with Axtell reverse cone megas. Ax's megas
were only 17 1/4" long, with an o.d. of 3 1/2", and a reverse cone 1 3/8"
long, with a outlet diameter of anything from 2 1/4" up. I generally used
them with a 2 3/8" outlet. The outlet diameter really depended a lot on the
engine tune. Ax told me once that the best was to put the bike on the dyno,
and keep opening up the outlet until the engine didn't rev as freely anymore
(his term was a "happy" engine), and then go back to the previous size.

I've seen flat track Nortons run straight pipes as large as 1 3/4", but I
don't have any experience with that size.

Is everyone now totally tired of exhaust system dimensions?

Ken C.
Click to expand...
 
As for porting and D shaped ports, yes, that is what you wind up with when you do not want to hamper flow by cutting down into the "short turn" floor of the port but you still want to increase the port area. In effect, the port is widened and raised while the floor untouched and, other than widening, is left alone, resulting in the shape of a D laying on its side. IMO, it is not that a D on its side is the best shape, it is the best compromise; the best shape would be round.

But back to head pipe diameter . . . . seems that some like 1.5" or even 1.625" and then the questions are length . . . . and megaphone dimensions . . . . but then I don't want to go there, this bike gets a muffler . . . .
 
Fullauto said:
My motor is very noticably stronger from idle up than when the standard head was fitted. Remember it's not all about size, but velocity of the flow as well.
Click to expand...

And more handsome! I need to start saving for one of those!
 
hobot said:
The MotorTune fella uses JBWeld, even on the intake side as well as exht. He says heat makes it pliable to still adhere with the thermal expansion.
On Exhat side, failure just blows right out on road but then the porting is ruined.
I've used JBW to replace a finger size cast iron barrel fin and it worked and stayed put, BUT it got malleable soft at running temps, which was ok as helped to mold it back even if I bumped it farting around forgetting the weak spot. I ran it on Peel then put on Trixie fine Until crap foil over paper head gasket blew out at oil hole and gas jetted the fake fin off and almost thru fuel hose too.
Click to expand...

So the Motortune man uses JB Weld. We are in the Dark Ages here in Ireland in terms of using epoxy. I have just finished doing exactly the same as you did — repairing a broken fin (on a Ducati 450 barrel). I had to search hard to get hold of a pack of Industro JB Weld. It was the best I could get over the counter here and is claimed to withstand 300 degrees C or 572 F. I am disappointed to hear that it softens at normal operating temperature. I tried Lumiweld and I think it's crap. I reckoned it was too close to the cylinder bolt hole to Mig weld it, hence the epoxy. I made a tiny pin and spacer to hold the fin in place so it won't droop if the stuff becomes plastic. Time will tell if the fix works.
 
On the power question or the quality of CS pipes I have no answers, but I have to say that my 850 sounded nicer running 1 1/2" system compared to 1 3/8" system the same style, (stock no-crossover and Toga P-shooters), or 1 3/8" S-pipes. 1 1/2" made for a deeper mellow sound. Maybe not faster, but pleasing to the ear. Next incarnation is 1 5/8" high pipes with shorties. Should be even more "colorful" but loud.
 
I have about 500 miles now on my 850. I put 1 1/2" sweptback pipes and pea shooters on because I think they look good. I got the pipes from Walridge, I don't remember where I got the mufflers, they are really nice english made ones.

My bike has stock everthing in the engine, an RH10 head and has a single 34 Mikuni.

This bike seems to have just as much power through the rev range, as my freinds 69 750 that has the PW 3 cam, and 9.5:1 compression. He has dual 30 mm Amals. Dunstall 2:1:2 1 3/8" exhausts. His bike never seems to pull away from mine. I know that on this forum it may be contriversial to say, but my stock 71 Bonneville is faster than either of these bikes. I think that is mainly because the Triumph is geared much lower and revs to 7000 RPM easily.

One of my Triumphs, an old flat tracker has very hot cams in it. It has about the most duration of any cam you can get for anything. I have done a lot of experimenting with this engine over the years. I managed to make that bike have much better low end torque by adding small steel pieces in the exhaust ports, that restrict the exhaust and give it the D shaped effect. (they are welded inside the threaded steel sleeves that screw into the Triumph exhaust port) I think this works because of preventing reversion at low speeds. It doesn't seem to restrict power at high speed either because of the way that the gas probably is pushed out to the outside radius of the port as it goes around the corner in the port.

Probably the 1 3/8" pipes would be beter for the street, but I doubt on the street you would really notice the difference. The amount of back pressure from the mufflers is probably more important to think about. Acually looking cool is probably the most important on one of these bikes really!

Nigel
 
tricatcent said:
I know that on this forum it may be contriversial to say, but my stock 71 Bonneville is faster than either of these bikes. I think that is mainly because the Triumph is geared much lower and revs to 7000 RPM easily.
Nigel
Click to expand...

What's the gearing on the Nortons?
 
Peel-750 liked Dunstall across full scope power band and with butt plate 2" hole had mellow deep base note under low throttle but I could hear it to around the ton on WOT. W/o the butt plate it was too loud for me, farm animals and police. I want to find a set of 1 5/8" header to cut up, whose got em?
They tried a Dunstall exhaust, with 1 5/8" pipes 28" - 30" long, and 24" mega with a 3" outlet and no reverse cone. It provided a good spread of power, but was too loud.
Click to expand...

MotorTune site is a pita to get around or find stuff but part 2 on porting methods has him saying JBW is your friend with highlighted photo of the tubes. Then gave tricks of handling the 2 part gray mix. On the fin repair it takes few hundred miles to harden up so can droop then harden if not taking care to remold after rides til it stays put. Painted over only the listee's will know.
Just before mounting Peels barrel it sat on carpet - I turned knocked over to hear clink to lose thumb size piece. I used greased tap over wood pieces to from it then trimmed excess to barrel contour. I'd forget it was there and almost knocked it off bumping it but it stayed on and re-molded back to nice.

Straight flow in a tube may work best in round profile but in a curved tube the D shape flows better. Basically D give less turbulence d/t less inside curve air mass flowing slower than the outer paths. Less shearing vortexes peeling off in D profile. At least that's what I've seen looking into the phenomena air craft, jet boats and log chutes of Viktor Schauberger ( 1885 - 1958 ).
http://www.rexresearch.com/schaub/schaub.htm
http://discaircraft.greyfalcon.us/Vikto ... berger.htm
"Big Bore" head pipes and mufflers


Actually what I will eventually end up with is rifling ridges in intake manifold, notches in chamber where inflow blast strikes and antelope twisted long funnel headers into vortex rocket muffler. One weird thing Viktor measured in nature's models of turbulence such as behind rocks in streams, a drop in temperature!
 
What's the best muffler core design? Louvered such as the Andover peashooter or the perforated such as the Wassell?


Hobot, you may have a point. When the pipe is straight, yeah, round is best shape for flow but when that pipe has to bend, then maybe, help the flow with a flat floor, relieve it by widening, in effect lifting the floor into the widened area to fool the flow into thinking it isn't turning . . . .
 
"Big Bore" head pipes and mufflers


The fellow who flowed my TT heads used epoxy to take the dips out of the inlet manifolds and ports, which came from the US.
 
I think people get too wrapped up in what's best for a race motor and forget what's best on the road. It's not how high the dyno curve goes but how much meat is under it. A motor that gives away power at the top end to fatten up the bottom end and mid range is going to ultimately be a much nicer and more useable motor on the road. With a motor like the Commando has, why would you want to move the power up the rev range? I just love that solid grunt from zero revs and wouldn't sacrifice an ounce of it for either "looks" or "sound". It's funny that neither Mick Hemmings or Matt at CNW (two of my distributors) have ridden a Commando with one of my heads on yet. I think when they do, they will be as impressed as I was when I got my bike back with the first head fitted.

I think it's telling that Kenny has picked up power with one of my heads and can't believe the mid range improvement which, after all, is what gets you out of corners, not a screaming top end. I must say that I'm not a believer in the "power band" theory where road bikes have a point where the engine really comes on and starts to go hard. Fine on a race track where you do the same thing at the same point on each lap and you can stay in the power band. It just doesn't happen on the road for various reasons such as blind corners, unfamiliarity with the lay of the land, other traffic etc. If you took a modern 200 horsepower sports bike, nipped fifty horsepower off the top end and gave it a huge fat torque curve, you would not believe what a ride it would be. It would be outstanding.

Personally, I think the modern factories have lost their way and are so involved in getting the fastest thing out there that they sacrifice true rideability to attain their goals. They also "refine" them and make them "sophisticated" and in so doing they thrash any character out of them that may have once existed. Rough edged motorcycles are what it is all about, as far as I'm concerned. i just wonder why you would want to ride something bland that does nothing for you as a riding experience.

One of my centrestand bolts fell out this afternoon on a pre dusk ride. The price we pay. Took five minutes to round up the spares and fit them. I'd still rather be working on the Norton than riding a Honda. And that, my friends, is the truth.
 
Fullauto said:
I think people get too wrapped up in what's best for a race motor and forget what's best on the road. It's not how high the dyno curve goes but how much meat is under it. A motor that gives away power at the top end to fatten up the bottom end and mid range is going to ultimately be a much nicer and more useable motor on the road. With a motor like the Commando has, why would you want to move the power up the rev range? I just love that solid grunt from zero revs and wouldn't sacrifice an ounce of it for either "looks" or "sound". It's funny that neither Mick Hemmings or Matt at CNW (two of my distributors) have ridden a Commando with one of my heads on yet. I think when they do, they will be as impressed as I was when I got my bike back with the first head fitted.

I think it's telling that Kenny has picked up power with one of my heads and can't believe the mid range improvement which, after all, is what gets you out of corners, not a screaming top end. I must say that I'm not a believer in the "power band" theory where road bikes have a point where the engine really comes on and starts to go hard. Fine on a race track where you do the same thing at the same point on each lap and you can stay in the power band. It just doesn't happen on the road for various reasons such as blind corners, unfamiliarity with the lay of the land, other traffic etc. If you took a modern 200 horsepower sports bike, nipped fifty horsepower off the top end and gave it a huge fat torque curve, you would not believe what a ride it would be. It would be outstanding.

Personally, I think the modern factories have lost their way and are so involved in getting the fastest thing out there that they sacrifice true rideability to attain their goals. They also "refine" them and make them "sophisticated" and in so doing they thrash any character out of them that may have once existed. Rough edged motorcycles are what it is all about, as far as I'm concerned. i just wonder why you would want to ride something bland that does nothing for you as a riding experience.

One of my centrestand bolts fell out this afternoon on a pre dusk ride. The price we pay. Took five minutes to round up the spares and fit them. I'd still rather be working on the Norton than riding a Honda. And that, my friends, is the truth.
Click to expand...

You really should take a KTM Superduke for a ride if this is the way you feel. Sorry, only 100 to 125hp at the wheel depending on the model and tune but fat torque curve, big midrange and revs like it has no flywheel. Real world bike, rough edges and all. This thing is all about the ride, it has to be because as is it isn't much to look at. One could say that beauty is as beauty does and that you can't see it when you're on it.
I hope to be able to get one of your heads in the future to go on my 850 P11.

Will
 
Yep Will, exciting grunt of mis-matched carb-manifold-head port and exhaust gave Peel off idle spunk that finished off sport bike contests in leans before they could even work up to next shift. Pissed me off if I got scared going into or over blinds I'd had deer-ATV's-Tractor+hay rake, log truck trailers or broken down cars just beyond.
The 900's and above could walk away no change to gain back till next 45'+ leaning then had to slow up or run over them.

Super motrards and 4wd drive rally cars are only thing I see as corner competition.
Caclulators imply Peel will have close to 100 lb-ft crank force just off idle. Consider that racer boys have to use brakes on super motards to kick rear out or super bikes lumps/bumps to get air borne to carry momentum. Peel can high side at will in straights as well as turns.http://hellforleathermagazine.com/2010/ ... #more-9447
 
Fullauto said:
I think people get too wrapped up in what's best for a race motor and forget what's best on the road. It's not how high the dyno curve goes but how much meat is under it. A motor that gives away power at the top end to fatten up the bottom end and mid range is going to ultimately be a much nicer and more useable motor on the road. With a motor like the Commando has, why would you want to move the power up the rev range? I just love that solid grunt from zero revs and wouldn't sacrifice an ounce of it for either "looks" or "sound". It's funny that neither Mick Hemmings or Matt at CNW (two of my distributors) have ridden a Commando with one of my heads on yet. I think when they do, they will be as impressed as I was when I got my bike back with the first head fitted.

I think it's telling that Kenny has picked up power with one of my heads and can't believe the mid range improvement which, after all, is what gets you out of corners, not a screaming top end. I must say that I'm not a believer in the "power band" theory where road bikes have a point where the engine really comes on and starts to go hard. Fine on a race track where you do the same thing at the same point on each lap and you can stay in the power band. It just doesn't happen on the road for various reasons such as blind corners, unfamiliarity with the lay of the land, other traffic etc. If you took a modern 200 horsepower sports bike, nipped fifty horsepower off the top end and gave it a huge fat torque curve, you would not believe what a ride it would be. It would be outstanding.

Personally, I think the modern factories have lost their way and are so involved in getting the fastest thing out there that they sacrifice true rideability to attain their goals. They also "refine" them and make them "sophisticated" and in so doing they thrash any character out of them that may have once existed. Rough edged motorcycles are what it is all about, as far as I'm concerned. i just wonder why you would want to ride something bland that does nothing for you as a riding experience.

One of my centrestand bolts fell out this afternoon on a pre dusk ride. The price we pay. Took five minutes to round up the spares and fit them. I'd still rather be working on the Norton than riding a Honda. And that, my friends, is the truth.
Click to expand...

Well said.

I guess my problem is that, although I've owned Commandos since 1971, my other current bike is an 08 CBR1000RR. I took them both out for a track day. Man oh man was the Commando a droner . . . fun, lots of compliments on "how fast that relic goes" . . . but . . . . and that wide ratio 4 speed . . . ugh . . . . but the thing is I love her . . . . far more than the CBR . . . . I just want a little more out of her . . . . . that's why I'm askin about 1.5" head pipes.
 
Well, Will, I'll tell ya something. I was in the local bike shop and saw the price of KTM nicnacs and keyrings and little billet covers and stuff. I couldn't afford them so I'd hate to think what spares prices are like. No Norton spare part has ever scared me price wise. On the Buells Down Under forum one of the guys was talking about track days in Queensland and he said one of the local dealers would come out with his Superduke and give it a flogging. The last he heard was that the guy was on his second engine rebuild and third gearbox. I can live without one I think.
 
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