I asked this very question of Hondaman a few months back. I do not believe he would mind if I shared his answer with you:
If your F3 cam is a stock F3 cam...the "F" and K7/8 cams had slightly
> more lift (not terribly significant), but their main feature was that
> they were delayed 5 degrees, relative to the earlier cams. That is, the
> intake valves open 5 degrees later than the ones on a K1-K6 (about 7
> degrees later than on sandcast K0), and the exhaust lobes on the "F"
> cams are longer duration for more scavenging of the cylinder. This
> former change was done to take advantage of the higher compression
> ratio, giving the bike a peppier feeling above 6500 RPM or so without
> extra loads on the crank bearings, while reducing the intake charge at
> 2500 RPM, so the bike could pass EPA rules of the later 1970s (i.e.,
> the engines were tested at 2500 RPM max). The exhaust change was
> partially EPA-related and partially to eliminate the plug fouling
> problems the earlier cams had when the bikes were ridden sedately. It
> also helped reduce 'bluing' of the exhaust pipes, because of less plug
> fouling.
>
>
>
> If you port the "K" head, you will get far more flow increase than the
> "F" cam would provide with its added lift, and at no penalty to the cam
> chain or tensioner parts. If you just drop in the "F" cam, you will
> find that a significant portion of your 3500-5500 RPM torque will
> disappear in favor of the higher HP when wound up tight. You may also
> find that the slide jetting must change (needle may have to drop a
> notch to keep the plugs clean): mainjet should stay at 105. The air
> screw may have to go in about 1/8 turn from where they are now, or
> change the pilot jets to #38 and use the 1 to 1.25 turn rule on the air
> screws, instead. If you both port the head and drop in the "F" cam and
> move it forward 5 degrees, you'll be impressed. ;-)
>
>
> If you install the "F" cam and also advance it 5 degrees, it's a
> different story: the jetting can stay the same and you will find some
> more midrange torque, plus enjoy cleaner sparkplugs overall. This is
> the "feeling" some SOHC4 riders report as "more power", because it puts
> a little more torque in the range where everyone actually rides.
> Certainly, if you make the switch, also use the X24ES-U ND sparkplugs,
> as they will give a nice midrange boost over the D8E plugs.
