Set them at .012, it will be fine and not too noisy.
Plus, its the recommended setting....
My theory ..is that the clearance allows lots of oil under the rocker pad....
I thought it was to let valve sit longer in seat and transfer the heat to the seat...especially when using the upper rpms, other side of the red line where it turns green again on the CB750 tacho I have.
More oil under rocker arm pad is another good thing. All cam installations must like that. This cam has not that abrupt opening and closing curves.
The data of the 315 has plenty of overlap. Megacycle 125-20 (photo) that has very fat lobes has even less overlap. DP315 look slim when comparing them.
BUT, the duration of the 315 cam is most likely designed for the huge lash of .012" (0.3mm closest gauge I have), which is double than other hot cams).
I'll change the lash if engine runs bad in need of less duration.
I have not calculated any numbers, IN might open like the other hot cams that is in the 29-25° range @ 0 lash (5-10° later) and overlap will be less too.
I need to check with different lash. The cam might work better with more lash. I guess it will when it is deigned that way.
I have set the lash with valve cover open after I timed the cam. Easier to see when rockers are on the base circle without fiddling with a small bent feeler gauge inside the small tappet holes from one side only when valve cover is mounted.
Now 0.15mm (.0666"), next is 0.20mm (0.0787") 0.25mm (0.098"), 0.30mm (0.0118").
Change valve lash is one way to tune the cam.
Lash of IN vs EX different, the only way to make difference between IN and EX on a SOHC.
OK, I'll changed my mind when writing this. The overlap cannot work well on the street with 4-4 as it is now. I'll change to 0.30mm. Sh_t, I have to to the adjustments thru the tappet holes when valve cover is mounted and most likely leak free.
Engine is in frame. Cut frame part not yet mounted (Frank's clamped weld free design)
I mounted the engine in frame alone. Lifted the engine without studs, cyl, head, clutch. All assembled with crankcase in frame.
What a different with new engine bolts with good threads and not banana shaped long bolts.
I have to start engine today so I'll start to adj the valves.
Back to the garage!!!!
EDIT: I finally understand why some experienced guys time the cam with correct running lash. Duration and overlap will then be seen as it will be.