In a big nutshell Eero
It depends on much more than just dialling the cams in to any degree settings that are recommended to you, in reality its a dicey game to play if not taken into consideration whilst building the engine!
It depends on the entire engine spec/build, the turbo you are planning on using and where you want maximum response to be, as every adjustment has gains to be made but against those gains (just like radical suspension setup's) there will be other areas that suffer losses.
For example....We recently built an engine which was going to run a large turbo where the guy who owned it was not bothered about bhp figures nor topend speed, he wanted as fast a spool time as he could possibly get with the best driveability & throttle response possible with what he initially had.
He was running a 278 profile cams which he wanted to be reused which were really inpractical for use in a ltd revving Gtir engine especially with big turbo (Gtx3078r) so we set about advancing both cams by just over three deg without knowing in reality what the outcome would be despite checking valve overlap and clearances.
But have to say that when i mapped the car the difference in spool time was much much better as was indicated by the previous dyno printout and the final one once mapped. It actually started spooling the turbo by around 1,200-1500rpm earlier with a big punch at higher midrange, but overall Bhp figure was down around 35bhp over previous but torque figure had increased by around 60lbft and the car felt 'without doubt' much faster all the way through rev range.
Aftermarket cams are generally preset from factory in order to give the best all round performance for a road car by using 0 adjustment on stock sprockets.
You would only use / need adjustable cam sprockets if you have a special setup in mind and you want the absolute best from which ever cams you purchase.
Did you take into consideration the valve overlap, compression ratio etc when you built the engine (assuming youve built it)???
You need to be very careful what you do regarding dialling in the cams because if you have built the engine to have a raised comp ratio (have decked block and skimmed head) and you are using high expansion race pistons such as JE and the like. When car is used in a race enviorement and temps are up you get your maths wrong then you could well end up with valve to piston contact.
So working out your clearances & allowing some leaway is very important that you get the figures right
The less overlap you run will determine (dependant on other factors) how good the idle will be
With more overlap (get your maths right) your idle will be lumpy but youll get much better top end power(which is ideal for drag type use).
By advancing the intake cam three deg and retarding the exhaust cam same amount the overlap between the cams will be increased and idle will be a bit lumpier, but youll get good mid range power without big losses in top end power.
Retarding both cams by around three degress youll get better top end power but with bottom end losses.
Advancing both cams (2.5deg with Hks 264) will give you much better low to mid-range torque / power but it will be with a topend drop in power
If you advance intake cam and retard the exhaust cam same amount valve overlap will be larger which will affect the idle and make it a tad lumpy' but youll have good mid range power & torque, with some losses in top end performance.
By retarding both cams by three degress youll have good top end power but will be at expense of bottomend and low to mid range performance also turbo response time will be reduced if your using a large tubby, which is not ideal for a road car that you use on a regular basis 'especially if your using a big turbo'
So if i were you i would:
1. determine use of the car
2. Power you want to run and where you want that power to be so turbo choice is the first key prior to build
3. Once above have been finalised then build your engine (do a dummy build up) then work out how much overlap you can get away with safely allowing leaway for the unexpected such as a mis-shift, heat expansion etc
4. I would initially 0 the cams and see how she performs once mapped........If you allow for overlap to be increased or decreased in the build up then at least you know you can do it safely by reduced risk of any valve to piston contact should an unrelated problem occur
Shit my fingers aching after all that typing