401 valve timing

[Guest 53and61]

In the restoration of my '61 Invicta, I'm finally getting to an elusive engine problem. I suspect that the valve timing is off. The base ignition timing @ 400RPM when I got the car was around 35deg BTDC! No pinging, but poor performance and roughness at low RPM. Performance got worse when I set timing to the specified 12deg. Vacuum and centrifugal advance seem to work fine. I'm a straight-8 oldie but a nailhead newbie--can it be that the 401 would run without pinging (or at all) at 35deg BTDC base timing? Does the crank balancer go on only one way or can it be put on such that the timing mark is way off? (I guess I could check this by turning #1 piston to TDC and checking timing mark position.) Is it possible to check valve timing without removing the timing chain cover as it is with staight-8s, or does the lack of solid lifters and adjustable rockers preclude this? Can one determine if valve timing is correct by watching the rockers with a timing light with the engine running?