So I've thought about replying to this, and thought about the follow up discussions that will result from this post. Here are my unfinished thoughts:
Firstly lets discuss the target rpms for each of the plate engines. I see lots of folks trying to spin the plate engines too fast, and quite honestly that is the mistake most dads make. But lets say a red plate is 4800, a green is 5200, a purple 5800 and a blue 6200. This can vary a bit depending on the track shape and size. Long, fast, flat out tracks favor lower numbers, short paperclip style higher.
So then lets look at our cam characteristics. This is a BSP3, my personal favorite for plate engines.
111° Intake Lobe Centerline as measured at .150" lift
.050" intake opening lift at 2°ATDC
.150" 38.5° ATDC
.200" 63° ATDC
max lift .233"
-.200" 22.5° BBDC
-.150" 3° ABDC
-.050" intake closing at 39.5°
duration 219° at .050"
Exhaust
107° Lobe Centerline as measured at .150 lift
.050" at 44° BBDC
.150" at .5°ABDC
.200" at 24°ABDC
Max lift .238"
-.200" at 55° BTDC
-.150" at 34° BTDC
-.050" at TDC
duration 224° at .050"
We can see we are dealing with a intake duration of roughly 219° and an exhaust duration of 224°. So say we find ourselves a very similar cam to use for a comparison. For example Comp Cams XS256S (which features an intake duration of 218, and an exhaust of 224, and an ILC of 106 a very close match indeed). You'll see it has a suggested rpm range of 1000 to 5600 rpm. It offers good torque and good idle characteristics. If we move the ILC of the Comp Cam to say 111-112° which is where most cams "land" on the Clone we can expect the ideal operating rpm range of the Comp cam to increase bringing the upper end of the suggested operating range to over 6000rpm.
So we see the rule set for the camshaft limits us (as it is intended to do), in terms of duration, overlap and lift. The comparison I made above with the Comp Cams was to give an example of the suggested rpm range of a cam of similar duration. I draw the conclusion that the BSP3 or CL2 isn't "too big" a cam for a plate engine. So if we can agree that the cam fits nicely with the rule set and the engines desired rpm range, then I would not want to go smaller in terms of lift, duration, and overlap. Lift maybe.... but that's a whole different thread right there.
I also think that this cam's appropriate rpm range works with where we intend to turn the engine, and can be optimized within the rule set by adjusting the ILC for our target RPM. So with all that said, IMO the "stock racing" cam isn't a bad choice at all.
I know you were looking for more detailed info, specific to overlap and duration. I guess through this long winded post, I'm basically trying to say I haven't experimented with changing the cam profile.
