I currently have a 103" 2008 Fatboy with SE211 cams and 50mm throttle body.

I've been looking at boosting the TQ and HP by adding new heads and S&S 625 Cams with 10.4 to 1 compression.

My tuner says the bike will be lumpy but still very rideable.

Anyone have any idea about whether this will work well?

Thanks

 

You will need headwork to optimize the performance from those cams; they will have to be decked to achieve the 10.4 CR. Not sure the stock beehive springs will handle the lift. IIRC, the SE beehive springs will handle .600" lift with .030" retainer to guide clearance. .625" lift sounds to me too close for comfort. Even if they handle the lift, seat pressure may not be adequate.

The cam specs indicate that you can't expect much from those cams until you hit 3000 rpms.

 

That's the set up I run and I love them but I wanted a fast top end bike. I haven't been out ran yet and they sound great but there are some sacrafices. They don't make power till top end, there not great for 2 up riding, and it hurt my gas mileage some but I couldn't be happier. I did change my valves and valve springs and I'm running 11.0 cmp with comp releases but it does run perfect on super unleaded with no spark knock. I'm not sure on my power but my builder said 110hp or better was his guess. Mine still has the break in tune because my builder wanted 500 miles before hus real tune was downloaded and I'm at 800 miles but can't seem to give my bike up for the week to install compensator sprocket and dyno probably this winter ill have it tuned. Good luck and if you have any questions you can email me
youtube.com/#/profile?user=dshizzle95z&v=nPFHxARHKtQ&view=videos .

Maybe that link will work I did it from my phone but its a video of mine idleing

 

Thanks to both of you for a detailed reply. Great feedback.

 

Just so we keep the record straight this was my tuner's response to these forum posts. These guys have been absolutely great to deal over the last couple of years so I thought it was only fair to give them right of reply.

"In reply to the forum responses- Re DJL – He is talking about very stock heads which wont handle anywhere near that lift. They are only good for 585” and don’t flow much more from about 500”. Your new heads are running double valve springs with the seat pressures set up for 625” lifts. The heads have been flowed to support the cams and are still flowing great numbers at 650”.

Re HDCrossbones09 – He is running 11:1 comp, we are setting your up at 10.4:1, changes things a lot. Sounds like he needs to get his tune sorted.

The goals of this build are as follows Make over 100HP and 100TQ at the rear. Keep the bike rideable in the lower rpm. Able to run happily on 98 octane. No compromise to reliability. I am planning to have 80FT of torque at 2500RPM. This will make for a very rideable bike."

I'm looking forward to getting this on the road soon so I will post back with numbers.

 

Not to nitpick but my comment on the heads was accurate. Had I known the heads were worked, the comment would not have been made.

Addtionally, you don't need long duration, hi lift cams to achieve 100/100 numbers and 80TQ by 2500 rpms can be achieved with a set of SE204 cams. I still have doubts about the low rpm rideability in this configuration. Spending the kind of money you are spending, I would expect 100TQ by 2500 or better. One of my bikes is a 95" Deuce and hits 90TQ at 2500 in the middle of a torque dip with bolt in cams. A 103" with 255 cams will make 100TQ damn near off idle. I suppose your tuner has also recommended roller rockers with those cams? Rollers are noisier than stockers and, coupled with the heavy valve seat pressures for those cams, valve train noise could be an isue.

I would also be interested in talking to a customer that has this same build as well as looking at his dyno chart. JMHO, let us know now it turns out.

 

With a cam that big 80 at 2500 isn't bad. That's not max TQ. A good tuner can map the fuel curve out so his bottom end would be adequate.

 

Maybe you are right; for the OPs sake, I certainly hope so. I guess it's just me but 80TQ at 2500 rpms is nothing to write home about regardless of cam size. If the OP wants to spend a lot of time between 3000 and 4000 rpms, he will be real happy with the build. But the first time a hot 95"er or 96"er shows him tail lights happy times are over. He might be able to reel'em in at 100mph but who rides there?

If I was the OP, I would want a proven build; see the results and talk to a happy customer. Trust but verify; the OP wanted to know if the proposed configuration would work well and depending on his expectations, it may work great but I remain skeptical. We shalll see, maybe I am FOS?

 

Guys not trying to be picky just trying to work my way through the minefield, and I really do appreciate your feedback - all of it!

I am the guinea pig in this scenario but I trust the guys to do a good job as they have in the past and they have been pretty conservative.

Cheers

 

I hope the build meets your exectations and, if it does, that's what counts. I don't doubt the mechanical ability of the guy turning the wrenches. But what concerned me was the target of 100/100 peak numbers and 80TQ at 2500 rpms. You just don't need long duration, hilift cams and a potentially noisy valve train to achieve that goal with 103". Please let us know how it works out.