2 inch pipe fishtails ????

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BCOWANWHEELS
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2 inch pipe fishtails ????

#1

Post by BCOWANWHEELS » Sun Jan 02, 2011 3:02 am

anybody know where i can buy old school type fishtails for 2 inch exhaust pipe ? i,ve looked everywhere and all i can find is for 1 3/4" pipe. I,am building a new set of up-sweeps for my old panhead chop and this is the look I want. i ported & polished my heads, big valves etc. and I dont want to choke it back down with 1 3/4 " pipes ....all help is appreciated ALOT......
BOB in Tn.



Cotten
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Re: 2 inch pipe fishtails ????

#2

Post by Cotten » Sun Jan 02, 2011 2:49 pm

Bob!

Do you want looks or performance?

If you have performance in mind,
I would suggest avoiding both fishtails and 2" pipes.

All they make is noise.

....Cotten

Bosheff
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Re: 2 inch pipe fishtails ????

#3

Post by Bosheff » Sun Jan 02, 2011 3:11 pm

I will not profess to be be an expert on head flow, as there are others who post here that are far more knowledgeable on this subject than I am. That being said here's my 2 cents worth. First of all there is a reason nobody markets a 2" pipe for a pan. My guess is that it would probably be more detrimental than beneficial as far as exhausting the cylinder head goes. You said you "ported and polished" yer heads and you "don't want to choke it back down with 1 3/4" pipes." In my opinion using a stock H-D pan cylinder head, even though it has been "ported and polished", you are not gonna make a large enough difference flow wise to take advantage of a 2" pipe. The major drawback in the panhead is not the size of the ports or valves, it is the fact that the fuel has to run through the intake and basically bounce off the back of the intake and do a 90 degree bend in both directions and do another less radical turn to enter the combustion chambers. While thoughtout port work will probably enhance fuel/air flow, I highly doubt what you did will make as large a difference as you might be expecting. A smaller diameter pipe will give you more bottom end torque if used with the right carb/intake set-up than a larger pipe would. If you were gonna be right on the red line all the time you were ridin the beast I might go with yer line of thinkin, but performance wise a 2" pipe is probably gonna hurt ya more than it helps. If yer talkin bout looks, that's another story, but in my opinion givin up performance for looks ain't where it's at, and I'm assumin you made the head mods for performance, right?....bosheff
Last edited by Bosheff on Sun Jan 02, 2011 3:32 pm, edited 1 time in total.

Bosheff
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Re: 2 inch pipe fishtails ????

#4

Post by Bosheff » Sun Jan 02, 2011 3:28 pm

Probably the main reason you can't seem to git yer mitts on the exhaust system you describe is that there is no real market for them, otherwise everybody and their brother would be sellin em....bosheff

Frankenstein
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Re: 2 inch pipe fishtails ????

#5

Post by Frankenstein » Sun Jan 02, 2011 4:41 pm

I ran 2" drags years ago on my Pan, (S&S 84"), and all they did was hurt performance. Ran much better going back to 1 3/4". I noticed it most at the high rev's.
However, I'd like to find a 2" fishtail for another project. Building a set of exhausts with no "Y" pipe, but still 2-1. I want dodge the restriction of the Y pipe, but not go with klunky, twisty duals.
DD

Cotten
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Re: 2 inch pipe fishtails ????

#6

Post by Cotten » Sun Jan 02, 2011 6:13 pm

And I'm no flow expert either,
but I know just adding tails can really mess up a fine running machine.
BUCOFISH.jpg
Not old enough to be 'old school'.
BUCOFISH.jpg (43.07 KiB) Viewed 3542 times
Its got something to do with the signal that dominoes back up the pipe to the head.

....Cotten
DD! True duals are "klunky"?

kitabel
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Re: 2 inch pipe fishtails ????

#7

Post by kitabel » Sun Jan 02, 2011 7:57 pm

A fishtail was originally a muffler, not a styling accessory.
The design: if the pipe is flattened, the area is always reduced (although the circumference or length around the outer wall remains constant).
Using a 2" ID pipe, just to make the math easier.
Circumference: 6.28"
Cross-sectional area: 3.14 in2 (square inches)
Squashed into a 2.90" tall × .250" wide rectangle (same circumference), area becomes: .72 in2, much smaller = big restriction.
Instead: make a new end-piece with the same width, but taller to increase the area.
6" tall × .250" wide = 1.50 in2, still less than 50% of the original open pipe.
However, it's much quieter (with no baffler) for 2 reasons:
1. the restriction
2. the 1/4" slot confuses some wave frequencies, if the slot is much wider they all pass through. Even narrower (less than 3/16") would be even quieter (more frequencies are damped), but it carbons up too quickly.

Conclusion: a fishtail has to be pretty open to have nearly the same area as an open pipe. I have an old 4" high tail for 1-3/4" pipe here, and it's about 3/4" wide at the bottom and nearly closed at the top, I estimate the area (as a triangle) as 1.5 in2, or only 62% of the open pipe area.
To make a fishtail for 1-3/4" OD pipe with no restriction (noise suppression by 1/4" slot only) it would have to be about 8-1/2" tall.
To measure a tail, use cardboard with graph paper on top. Race the tail down, and rap the top with a mallet to indent the paper. Count the squares, etc.

Cotten
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Re: 2 inch pipe fishtails ????

#8

Post by Cotten » Sun Jan 02, 2011 9:25 pm

kitabel wrote:A fishtail was originally a muffler, not a styling accessory.
The design: if the pipe is flattened, the area is always reduced (although the circumference or length around the outer wall remains constant).
Using a 2" ID pipe, just to make the math easier.
Circumference: 6.28"
Cross-sectional area: 3.14 in2 (square inches)
Squashed into a 2.90" tall × .250" wide rectangle (same circumference), area becomes: .72 in2, much smaller = big restriction.
Instead: make a new end-piece with the same width, but taller to increase the area.
6" tall × .250" wide = 1.50 in2, still less than 50% of the original open pipe.
However, it's much quieter (with no baffler) for 2 reasons:
1. the restriction
2. the 1/4" slot confuses some wave frequencies, if the slot is much wider they all pass through. Even narrower (less than 3/16") would be even quieter (more frequencies are damped), but it carbons up too quickly.

Conclusion: a fishtail has to be pretty open to have nearly the same area as an open pipe. I have an old 4" high tail for 1-3/4" pipe here, and it's about 3/4" wide at the bottom and nearly closed at the top, I estimate the area (as a triangle) as 1.5 in2, or only 62% of the open pipe area.
To make a fishtail for 1-3/4" OD pipe with no restriction (noise suppression by 1/4" slot only) it would have to be about 8-1/2" tall.
To measure a tail, use cardboard with graph paper on top. Race the tail down, and rap the top with a mallet to indent the paper. Count the squares, etc.
"Eight and a Half" Fishtails would get attention.

What more could you ask for!

Huge "Echo Cans", like Underdoggie?
Underdoggie at Wauseon 2010.jpg
Underdoggie at Wauseon 2010.jpg (169.32 KiB) Viewed 2221 times
....Cotten

BCOWANWHEELS
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Re: 2 inch pipe fishtails ????

#9

Post by BCOWANWHEELS » Mon Jan 03, 2011 1:03 am

THANKS FELLAS FOR YOUR THOUGHTS ON 2" PIPES. I CAN FAB BAFFELS TO GO INSIDE MY PIPES TO TUNE THEM FOR THE BEST TUNE UP BUT I DONT LIKE THE NECKED DOWN LOOKS OF 1 3/4" PIPES. I BEEN TOLD SAMSON MAKES THE 2" TAILS GONNA CALL THEM SOON.
BOB

BCOWANWHEELS
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Re: 2 inch pipe fishtails ????

#10

Post by BCOWANWHEELS » Mon Jan 03, 2011 6:27 am

HERES WHAT I,VE BEEN LOOKING FOR.
THANKS GUYS
http://bikergarage101.com/08876fishtailtip2x7.aspx" onclick="window.open(this.href);return false;

Kuda
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Re: 2 inch pipe fishtails ????

#11

Post by Kuda » Thu Jan 06, 2011 2:59 pm

While I agree with everyone on the use of 2" pipes on a street motor (bad idea), I did help a friend once who had the same idea. Had specific "look" in his mind on what his pipes should look like, and I couldn't talk him out of it. So we compromised: I ended up using 1 1/2" pipe inside a 2" pipe. It was a stone bitch to bend up (had to go to my local exhaust shop to borrow thier heavy duty bender)and I ended up having to plug weld a couple of spots to stop rattling, but it looked the way he wanted and sounded pretty good, and ran better than it had a right to. He also insisted on using "torque cones" on the same stock 74" low compression pan motor. And so I did: turned 'em around and used 'em as adapters to hold the 1 1/2" pipe inside the 2" pipe. Now he brags all day about how he was right about using the 2" pipe and torque cones. I just smile and nod, 'cause he still has no clue... :mrgreen:

-Kuda
'49 panchop

ps. Yes, they were heavy as hell, but they were also fairly short, so... :roll:

Bosheff
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Re: 2 inch pipe fishtails ????

#12

Post by Bosheff » Thu Jan 06, 2011 3:57 pm

Pipe length is also a critical factor when it comes to efficient scavenging of exhaust. The length of the pipe has a tremendous effect on where in the powereband the engine makes it power/peak power, and/or falls on its face. This, teamed up with pipe diameter tells ya alot about an exhaust system's capability before you ever install it on the engine. In a true performance engine scenerio, the exhaust system is just as important as the compression ratio, cam, or induction set-up. All componernts must work together to extract maximun horsepower in the desired R.P.M. range....bosheff

kitabel
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Re: 2 inch pipe fishtails ????

#13

Post by kitabel » Thu Jan 06, 2011 6:33 pm

X2, a wave returning at the right time can have the same effect on the intake system as about 3-4 lbs. of boost (very briefly), far stronger than a tuned intake length.
However, the effect gets very complicated if the pipe is very long. If a wave meets its own echo coming back from the valve several times, each collision sets up another reflection - which strikes all previous.
Heavy traffic damps the signals, making length choice more like guesswork.

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Re: 2 inch pipe fishtails ????

#14

Post by kitabel » Thu Jan 06, 2011 6:39 pm

The damage from a 1-1/2" use on a panhead is mostly from the transition - the gas hits a wall - but if a cone or tapered transition is provided it works just fine.
90 hp Norton, Triumph and XR used 1-1/2" pipe, and it also produces a stronger wave reflection for tuning.
Then why did they use larger pipe?
Because if there is no tuned length (siamese pipes with restrictive muffler, moderate engine speed and low overlap), the next best plan is to reduce exhaust pumping loss - bigger is better. That's why older flatheads have such big exhaust valves - it's not a mistake, just a different plan.

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Re: 2 inch pipe fishtails ????

#15

Post by Panshovevo » Thu Jan 06, 2011 10:51 pm

Kitabel, I've picked up bits and pieces of exhaust theory over the years, but never really got a good understanding of it. Can you recommend any specific reading material that might help me tie it all together?
Regards,
John

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