Re: Flat spot down low???
Harmonic balancers can, and do slip.
They consist of 2 seperate cast pieces, 1 the center hub which slides onto the crankshaft and is located by the key, and 2, the outer ring which is seperated by a high density rubber. This is to damp out harmonics, hence the name.
The outer ring quite often slip out of adjustment when they get old and the rubber starts to perish.
Check to see if it is on true TDC by removing number 1 spark plug and use a bit of wire to locate exact TDC, then see where your mark is on the balancer.
4L I6, naturally aspirated producing 173.5rwkw.
14.410 @ 96.49mph with street radials.
What's that?..... Did I hear you say TQE power?