Alright, I think I'm following here. The torque converter isn't coupling until well past the torque peak of my motor, and when it finally does at 5200 RPM is the reason we see the spike.
That’s how it appears to me.
By the looks of the graph, I’d say it starts to couple effectively at about 5000, and at around 5200 or so when it’s more fully locked up, it’s well past peak tq and you’re well into the downhill side of the tq curve of the motor, which is why it’s dropping off quickly right after it shows the peak.
It’s not until the converter is basically locked up that the power curve will mimic the engine power curve........and in this case that seems to be happening well beyond the engines tq peak rpm.
You should do the flash stall test to see if it agrees with what appears to be happening on that sheet.
I can’t believe there is any way a converter that was “right” for a small block would be correct behind a lower/mid rpm high torque 511.
I’m not sure exactly what kind of driving experience you’re looking for, but the OD trans and 230@.050 cam, unported std port heads, dual plane manifold....... kinda looks like a 3000-ish flash stall combo to me.
Which would likely be a pretty tight(very tight?) 11” unit.
As an illustration of how tq affects stall speed, the 8” converter I ran behind my 340 and then the 383.
4800 behind the 340, 5400 behind the 383.
Depending on what your what your SB combo was, I can easily see where the 511 could be 200ft/lbs better, especially down near where the converter would have stalled behind the SB.
And a difference in tq like that will have a huge impact on how the converter behaves.
Frankly, I’d think it should be pretty high on the list of things that should be changed.
