100" big bore on 03 Ultra

[chas]

I pulled the trigger with the 100" big bore for my 03 Ultra! I will start the tear down after Xmas. I am currently running the s&s 509c cam. How will this cam run with the higher 10:5 1 cr? Is it going to work to its potential or is it not a good choice for getting the most out of the extra power. I am looking to max the low to mid range torque. I will be doing some light head work. Should I change springs to beehive while in there, or is the bike going to be ok with stock? Maybe go to larger injectors, and intake? Thanks in advance with your thoughts

[RoadKingKohn]

If you do a search you will find what others have done along with DYNO results posted.

[Hossamania]

From what I understood, the 509 was set up for mostly stock 88" motors, the 510 for a little higher compression motor with more cubes.

[rigidthumper]

The 509 was made for stock 88" 8.1:1 compression. Do you have manual compression relief valves installed?

[djl]

JMHO but better cam choices for 100" displacement.  OEM valve springs will accommodate cam lifts to .510; I have read that some have gotten by with .525" If head work is part of the plan, don't short cut an area offering significant gains. Consider replacing valve springs (yes beehives) that will accommodate .600" lift to open up cam choices and talk to the head porter about cam choices.  The big bore kit must come with domed pistons to hit 10.5 static? At that compression, compression releases as rigidthumper suggests would be adviseable.  Cam choices are going to be limited to cams with later intake close events to keep CCP at or below 200psi, something like the S&S 585 or Cyclerama 595; don't know if OP is running geared or chain cams which could impact cam choice. Sounds like the OP needs to nail down a plan; the devil is in the details.

[Hossamania]

Couldn't agree more with djl. Have a plan. (And yes, definitely new valve springs.)

[Deye76]

If doing valve springs, S&S .570 would get that heavy ultra going. 

[m1marty]

I would not recommend the 509 at anywhere near 10.5. Especially in a barge

[Mi Infidel]

S&S 510 would be a better choice if you don't want to upgrade the valve springs.

[Ohio HD]

S&S 510 is not a good fit if he goes to 10.5:1 static compression. He'd be better off with Andrews 31's or 50's if he doesn't upgrade the valve springs. If he upgrades the valve springs then there are many cams that are a good fit.

[kd]

CR575