Engine Power Loss Under Load

Need help to figure this one out. ‘69 Eliminator, 428cj, auto trans. I use to be able while stopped, to brake while applying throttle and roast the rear wheels with lots of smoke and righteous black marks. Over the course of the past 2-3 years this has degraded to stalling the engine and nothing more. What can change with nothing else done to the car for this situation to happen?


Hmmm… vacuum leak or failing transmission modulator, or a small leak in the lines to the modulator?

Timing is good and I’ve been checking for vacuum leaks. The only leak I’ve found so far is the headlight actuator and I just rebuilt that with a kit from WCC. Didn’t change the performance so I’ll keep searching. Thanks for your input, it’s much appreciated!

The stator one way clutch in the torque converter could have failed. Slowly apply the throttle to max stall speed. If it is under 1200, the one way isn’t holding. Converter replacement is necessary at that point

I’ll check that out and see what happens. Thanks

Have you been using or added the ZDDP oil additive. Cams can go flat and the power with it.
Put a vacuum gauge on it that should give you some hint of where to look.
See the video for the cam problem:

Thanks for the feedback. This is definitely a consideration and I’ll check it out. On a side note, I’ve spent the past 2 hours binge watching his videos with more to go. This is a great YouTube channel. Much appreciated!