It's really difficult to discuss cam selection in a 50 word forum response. Often times, we are in agreement, even though we are coming at something from two different directions.

As we all know, cam selection is not simply a matter of finding the cam with the highest lift and longest duration and stuffing it in our motor. Selecting the proper cam is a complex matter of determining first what we are trying to accomplish, and then match all the motor componants to the task. Building a motor for drag racing is different than building a motor to pull large loads over long distances.

It pretty much goes without saying that your cam selection has to match the rest of your engine componants. Putting in a cam with too much duration will kill a street engine because it's designed for high rpm valve events, and at slower rpm's the valves are open too long and the cylinder is bleeding off pressure it needs to build torque. As rpm's rise, valve events happen much more quickly, and a long duration cam is needed to make sure the cylinder has time to fill. At low RPM's, it becomes a detriment, because the piston is already coming back up the bore, and the cylinder will not be able to build as much pressure prior to ignition.

This is one reason engine builders increase compression with a longer duration cam. You can gain the benefits of higher compression without getting a detonation penalty. In small block chevy motors, we would generally run a 270 degree (duration) cam in a 9:1 motor, 280 degree cam in a 10:1 motor, and a 290 degree cam in a nearly 11:1 motor. That's a generalization, but a fairly well accepted rule of thumb.

And of course, when your motor is spinning faster, you need to make sure your valve train can move faster, valve springs need to be stronger with higher compression or your valves stop working properly, your heads need to be able to flow higher volumes of air/fuel more efficently, and so on.

High RPM motors are different in many ways than low rpm motors. The faster the motor turns, the less time the cylinder has to fill, fire, and expend. The valve train needs to be working so much more efficently at higher rpms.

We build our motors in 'stages' because we need all the componants to be working in harmony to provide the best performance for our desired task.

 

Anyone know if I'll be able to still use my Vance & Hines Fuel Pack after SE255 install? E-mailed V&H last week for map but no response.

 

Depends. There are a few settings charts for 07 touring bikes with 255 cams, but I think they're all based on 103 motors, and either a stage I or stage II download. I ran up against the same wall, and finally jumped ship.

 

NO.... I don't think you will be happy keeping the fuel pak! As you already found out.... very limited info/feedback from tech support, and it will never give the proper adjustment abilities for what you will need to dyno tune your cams. You can try, but a download will produce better results than the fuel pak.. I hear alot of good things about TTS and Thundermax. I have the SE Pro tuner but I'm still not so sure about it. Dyno tuning problems are haunting me. Maybe it's just the dyno tech. Good luck none the less.....

 

I went with the SE 103" Stage II in my ultra about two weeks ago. Download from fuel moto and it feels like a new bike. Acceleration is much improved, and Sixth gear is now usable. Nothing but grins now.

 

I'm doing by bike bas achwards of what most people do. I have the SERT, FatCat and good air cleaner and I put a set of HQ500 cams it my bike, I have also added the 49T Evolution ring gear to my bike.
My bike makes 90 hp and 93 lbs of torque that is almost flat from about 2200 RPM to 5000, the combo of this cam and the slightly different gear ratio work perfectly together.
I am currently saving up to have the heads ported by HQ's and bump the compression to 10-1 I an am hoping to add 5-10 to both HP and Torque but how knows. At any rate I'm sure I will have the best 96" around.

 

What kind of problems?
Thanks