[blykins]

I've seen 100hp drops from flywheel to rear wheel on Cobras. Sidepipes and drivetrain losses are usually killers.

A good single carb intake and carb package would probably wake that thing up a little bit. It should pull a little higher than 4900, so something is amiss somewhere.

Any signs of valve float at higher rpm? Usually the springs that they put on these heads (especially small heads like a 170) peter out pretty quick.