[Barry_R]

I think its on the high side, but a Cobra weighs next to nothin' so it'll never load the engine that hard. You may well get away with it.

A good hand on distributor curve work (or some electronics) will allow you to idle with a closed throttle and low enough low RPM timing to avoid dieseling.

A touch more cam would not hurt a thing in most combinations - especially one on the edge of detonation. The det will hurt a lot more...and dropping some low RPM cylinder pressure might just do the trick. At higher RPM the event speed works in your favor.

Cylinder head chamber design plays into this a lot. A traditional FE wedge needs a bunch of timing to make power. The BT or reworked Ed heads with a contoured shape will run with very little timing.