Those two XE series cams have a taxi cab - like idle. The car ran better with the 268H, and better still with the 270H. No problem with all power accesories including vacuum powered hide away headlights and power brakes.
If this is for a Cobra kit car that has manual brakes and no vacuum accesories then why not step up to something more substantial? All these cams are really mild. With a manual trans and a 428 something like a Comp 294S is a real blast to drive.
1912 Model T Ford touring Salmon (ugh!)
1913 Model T Ford Touring original Black paint
1915 Model T Ford Roadster Black
1915 Model T Ford touring Black of course!
1967 Cougar GT 390 Cardinal Red / Black
1968 Cougar GTE 427 Augusta Green / Saddle
http://www.supermotors.net/vehicles/registry/15029/50071-2