I have a 2010 Fat Boy w/ V&H Big Shots, Zipper's Max Flow A/C, and a TTS Master Tune.

I want the best of all worlds: lots of bottom end that doesn't drop off at 5000 RPM, and good gas milage.

I asked a tuner about better cams since I already addressed the breathing issues, but he told me that with my engine, milling the deck alone will yield plenty of power, and I can do the cams later if the milling alone doesn't do it for me. Anyone have experience with milling the deck alone aster Stage 1?

My other question is, at what point does upgrading the injectors and ignition prove worthwhile?

Thanks.

 

It is true that the motor would benefit from some additional compression, the OEM EPA compliant cams will not respond nearly as well as performance cams. Without getting into the weeds, decking heads before selecting cams is not a good move. Chamber volume and the intake valve close event of the selected cams determines corrected and cranking compression. The stock head chambers usually measure between 85cc-86cc but I have seen them measure near 90cc. Chamber volume should be set based on the intake valve timing, i.e., close event and the desired corrected and cranking compression. Decking the heads now and selecting a cam later will limit the cam choices available to you.

Unless you are going big, like 1178" or 120", larger injectors won't help. Your bike is fule injected and the ECM can be programmed with the TTS system, so you really don't "upgrade" the ignition. Programming ignition timing is part of the dyno tuning process.

A set of Andrews 48 cams and a retune would be a nice upgrade from Stage I with the stock heads.

 

Generally, you need to decide on your overall goals, and then build the motor to suit. DJ is spot on with his advice, milling the heads in advance of choosing a cam is putting the cart before the horse. A cam is nothing more than a timing device, it controls the opening and closing of your intake and exhaust valves. The sequence in which that happens will dictate where your powerband is located. You get a band of about 3000 rpms where your motor is making the most power. It's up to you (and your cams) to decide where that powerband is located.

The stock cams are as restrictive to performance as the stock exhaust system. The complete lack of overlap is good for emissions (very little unburned fuel escapes with the exhaust gasses), but restricts scavenging, which isn't so good for performsnce. Your heads are capable of pushing quite a bit more air through them if you'd let them.

If you do decide to pull the heads for some reason, like milling the decks, you're exactly zero bolts away from pulling the cylinders and pistons. If you're doing the work yourself (highly encouraged), it will take you about a half hour or so to swap pistons and jugs, once the ring gaps are set.

You'll get a little bump in compression, and better combustion if you swap to a .030 head gasket when you bolt it all back up, so that should figure in your plans as well.

 

You guys are great, thanks for your advice.
I used to build smallthe block engines for my Mustangs, and worked on small block Chavys as well- back in the early 1980s. I'm rusty, and my knowledge of fuel injection, ignition, and Elms is limited.
I did find it odd to up the compression before working the heads and installing performance cams.
If pulling the cylinders is simple at that point, it seems like I should go to 107ci at that point
Agreed? If not please continue educating me.
Thanks!

 

You can go to 103" by boring cylinders and installing SE cast flat top pistons to fit the 3.875" bore. You would have to bore to 3.932" to increase displacement to 107" and go to aftermarket forged pistons like Wiseco, JE or CP. I like the H-D pistons and cylinders but there are plenty that do go to 107". There are cylinder/piston kits from Axtell, Rev Performance, SnS, TMan, etc. Those kits can be expannded to include heads and cams for a complete package. Rev Performance includes an EFI tuner with their kits. How fast do you want to go = how much money you go to spend.

 

Is it worth the money to go to 107ci, or is the gain in performance minimal? Since going to 107ci instead of 103ci only mean a larger bore, so it seems logical to skip 103ci and just go toto 107ci- unless that means work on the crankshaft. Since I haven't bought the cams yet, now is the time to make that decision. If I need to change the heads for 107ci, then I have to rethink my budget.
Thanks for everyones continuing assistance.

 

We seldom take a clients 96"er to 103", as the 107" bore is a no-brainer.
We usually do not, however, try to sell a 107" kit to a 103" owner as the 4 inches just ain't worth the dollar.
But that said, a 107" with a good set of cylinder heads, cam, exhaust combination(and perhaps a throttle body upgrade as well) can, and is, a formidable powerplant.
Surfacing the heads prior to the addition of a cam swap, is setting the stage for detonation issues, and we do not reccomend that.
Best to pull it all togather at one time.
Scott

 

Really no more $$ to bore to 107"; a bore job is a bore job. You don't have to change heads for the larger bore. Whatever head work you planning, or not, for a 103" motor will be fine for a 107" motor. You do need to run the compression numbers and select cams first, then build around the cams.

 

As I stated, "I did find it odd to up the compression before working the heads and installing performance cams," so I guess I'm not totally rusted over.

Scott, You said, "a 107 with a good set of cylinder heads, cam, exhaust combination(and perhaps a throttle body upgrade as well) can, and is, a formidable powerplant." Well, I already have V&H Boig Shots (w/baffles) and a Zipper's A/C, so I would want to match up to the exhaust I already have. When you say, "a good set of cylinder heads," are you talking about changing the heads, or taking my heads and having them ported & polished, new valves lapped in with new springs, etc.? Also, when you say, "perhaps a throttle body upgrade as well," are you suggesting that is my choice as opposed to the needs of the rest of the work you suggest?
My goal is as follows: for my Fat Boy to be a rocket off the line; when I'm cruising on the highway be able to downshift and pass almost fast enough for the driver I passed to second guess if I had been behind him all those miles, or vice-versa; cruise hundreds of highway miles while getting good gas mileage.
Many more thaks!
Rob

 

Sorry to double post, but my conscience just kicked in.
I don't want to do burn outs, and I don't want to do wheelies. I also don't want to have to find out that I will need to change my pulley ,belt, etc. after I do the engine work- I'd like to be able to wait to do those things when I need the next tire change.
Maybe I don't need a radical 120 HP & TQ, but I do want at least 100.

** I just remembered I am going to be 49 in 3 months and this bike may end up being my sons ride, with me going to a bagger in another 3 years.

I hate being responsible sometimes.