Fat Bob - stock headpipe big bore builds?
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Grand HDF Member
Joined: Nov 2017
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From: Texas
Fat Bob - stock headpipe big bore builds?
Has anyone out there built a big bore using the stock Fat Bob headpipe?
I've got the Fat Bob, with the stock header and the S&S mufflers, and frankly I have zero interest in changing out the exhaust. I like how it looks, I like how it sounds, it's perfect for this bike. And with my bike now being out of warranty, and FuelMoto offering their $2799 128" kit, that looks really tempting. But will it work? FuelMoto is quite concerned about the exhaust system, as they haven't had anyone build one using the stock header, and they are advising to go with a D&D. I'm sure the D&D is a fine pipe, but I don't want to spend ~$900 to get something that changes the look of the bike and makes it a lot louder than it currently is. I'd rather keep the stock header, even if it means losing that top 10 hp or whatever. As long as it shows good solid gains over the existing build, that's what I'm looking for.
Has anybody put on (for example) FuelMoto's piston & cylinder kit, with the stock exhaust header, and had it dyno'd?
For reference, I'm aware of this build: https://www.hdforums.com/forum/softa...rformance.html
That looks great! Only thing is, that's a full Harley Stage IV with new heads and a TTS200 horsepower cam. It really looks good, and has me optimistic that the exhaust is up to the job, but I don't want the Harley Stage IV 117 kit, I don't want to mess with potentially out-of-round cylinders or breaking valve springs and high compression, I'd rather have a high torque bolt-in cam and modest compression and make up the power with displacement. But it seems the exhaust is up to the task of delivering at least 125 hp, but -- would it work in connection with the big size, stock heads, and lower compression? Without verification it's a pretty expensive gamble, so I'm just asking: anyone out there done anything similar that they can share? Thanks!
I've got the Fat Bob, with the stock header and the S&S mufflers, and frankly I have zero interest in changing out the exhaust. I like how it looks, I like how it sounds, it's perfect for this bike. And with my bike now being out of warranty, and FuelMoto offering their $2799 128" kit, that looks really tempting. But will it work? FuelMoto is quite concerned about the exhaust system, as they haven't had anyone build one using the stock header, and they are advising to go with a D&D. I'm sure the D&D is a fine pipe, but I don't want to spend ~$900 to get something that changes the look of the bike and makes it a lot louder than it currently is. I'd rather keep the stock header, even if it means losing that top 10 hp or whatever. As long as it shows good solid gains over the existing build, that's what I'm looking for.
Has anybody put on (for example) FuelMoto's piston & cylinder kit, with the stock exhaust header, and had it dyno'd?
For reference, I'm aware of this build: https://www.hdforums.com/forum/softa...rformance.html
That looks great! Only thing is, that's a full Harley Stage IV with new heads and a TTS200 horsepower cam. It really looks good, and has me optimistic that the exhaust is up to the job, but I don't want the Harley Stage IV 117 kit, I don't want to mess with potentially out-of-round cylinders or breaking valve springs and high compression, I'd rather have a high torque bolt-in cam and modest compression and make up the power with displacement. But it seems the exhaust is up to the task of delivering at least 125 hp, but -- would it work in connection with the big size, stock heads, and lower compression? Without verification it's a pretty expensive gamble, so I'm just asking: anyone out there done anything similar that they can share? Thanks!
Last edited by FatBob2018; Mar 6, 2020 at 12:17 PM.
Road Warrior
Joined: Feb 2014
Posts: 1,851
Likes: 420
From: Santa Fe NM
I will keep looking but I am almost positive someone has posted about this and how well the stock exhaust actually performs.
Edit: I may be mistaken and it was a stage 2 not a big bore build.
Edit: I may be mistaken and it was a stage 2 not a big bore build.
Last edited by Bowhunter8607; Mar 6, 2020 at 12:39 PM.
4th Gear
Joined: Feb 2020
Posts: 8
Likes: 0
From: Denver
I did the s&s 128 and 475 cam chest and SE heads with stock intake, headpipe with Tab slip ons and it worked great on my fatbob.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
Cruiser
Joined: Jan 2019
Posts: 110
Likes: 24
From: Bratislava
I did the s&s 128 and 475 cam chest and SE heads with stock intake, headpipe with Tab slip ons and it worked great on my fatbob.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
Thread Starter
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Grand HDF Member
Joined: Nov 2017
Posts: 4,252
Likes: 3,135
From: Texas
I did the s&s 128 and 475 cam chest and SE heads with stock intake, headpipe with Tab slip ons and it worked great on my fatbob.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
i eventually got the fatcat exhaust and breather but I really didn't need to, only to try to squeeze a few more ponies out it.
Go for it. It's a good sleeper build.
4th Gear
Joined: Feb 2020
Posts: 8
Likes: 0
From: Denver
I need to dig it up but sure I'll post it when I find it. It was 125/145 I believe with max torque at 3500 rpms
HD EFI Guru
Joined: Jan 2008
Posts: 4,494
Likes: 4,781
Has anyone out there built a big bore using the stock Fat Bob headpipe?
I've got the Fat Bob, with the stock header and the S&S mufflers, and frankly I have zero interest in changing out the exhaust. I like how it looks, I like how it sounds, it's perfect for this bike. And with my bike now being out of warranty, and FuelMoto offering their $2799 128" kit, that looks really tempting. But will it work? FuelMoto is quite concerned about the exhaust system, as they haven't had anyone build one using the stock header, and they are advising to go with a D&D. I'm sure the D&D is a fine pipe, but I don't want to spend ~$900 to get something that changes the look of the bike and makes it a lot louder than it currently is. I'd rather keep the stock header, even if it means losing that top 10 hp or whatever. As long as it shows good solid gains over the existing build, that's what I'm looking for.
Has anybody put on (for example) FuelMoto's piston & cylinder kit, with the stock exhaust header, and had it dyno'd?
For reference, I'm aware of this build: https://www.hdforums.com/forum/softa...rformance.html
That looks great! Only thing is, that's a full Harley Stage IV with new heads and a TTS200 horsepower cam. It really looks good, and has me optimistic that the exhaust is up to the job, but I don't want the Harley Stage IV 117 kit, I don't want to mess with potentially out-of-round cylinders or breaking valve springs and high compression, I'd rather have a high torque bolt-in cam and modest compression and make up the power with displacement. But it seems the exhaust is up to the task of delivering at least 125 hp, but -- would it work in connection with the big size, stock heads, and lower compression? Without verification it's a pretty expensive gamble, so I'm just asking: anyone out there done anything similar that they can share? Thanks!
I've got the Fat Bob, with the stock header and the S&S mufflers, and frankly I have zero interest in changing out the exhaust. I like how it looks, I like how it sounds, it's perfect for this bike. And with my bike now being out of warranty, and FuelMoto offering their $2799 128" kit, that looks really tempting. But will it work? FuelMoto is quite concerned about the exhaust system, as they haven't had anyone build one using the stock header, and they are advising to go with a D&D. I'm sure the D&D is a fine pipe, but I don't want to spend ~$900 to get something that changes the look of the bike and makes it a lot louder than it currently is. I'd rather keep the stock header, even if it means losing that top 10 hp or whatever. As long as it shows good solid gains over the existing build, that's what I'm looking for.
Has anybody put on (for example) FuelMoto's piston & cylinder kit, with the stock exhaust header, and had it dyno'd?
For reference, I'm aware of this build: https://www.hdforums.com/forum/softa...rformance.html
That looks great! Only thing is, that's a full Harley Stage IV with new heads and a TTS200 horsepower cam. It really looks good, and has me optimistic that the exhaust is up to the job, but I don't want the Harley Stage IV 117 kit, I don't want to mess with potentially out-of-round cylinders or breaking valve springs and high compression, I'd rather have a high torque bolt-in cam and modest compression and make up the power with displacement. But it seems the exhaust is up to the task of delivering at least 125 hp, but -- would it work in connection with the big size, stock heads, and lower compression? Without verification it's a pretty expensive gamble, so I'm just asking: anyone out there done anything similar that they can share? Thanks!
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4th Gear
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Grand HDF Member
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From: Texas
Thanks!
That's almost exactly what I am looking for. A little earlier torque would make it perfect, but honestly I don't have any right to complain; that build is showing more torque at 2500 than my stage 2 bike has at peak!
Outstanding. Thanks for digging that up.
That's almost exactly what I am looking for. A little earlier torque would make it perfect, but honestly I don't have any right to complain; that build is showing more torque at 2500 than my stage 2 bike has at peak!
Outstanding. Thanks for digging that up.