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i had the mechanic look at the bonne. he agrees there is a knock, but says it isnt acting like a rod knock. he is thinking broken flexplate, torque converter, or transmission internally. he thinks the engine is fine. he explained why he feels that way and at this point i think i agree. he said that it doesn't seem like a "hard knock" and that it inst a rhythmic type of knock. it also doesn't sound like it is coming from the lower end. so the engine isnt the problem, its probably a flexplate. dealer said they would repair the car. im happier knowing that it might be something like a flexplate and that would mean there is less of a chance of the dealer trying to do a botch job on it. once this is all fixed is the 87 bonne a fairly reliable car?

Wonder if they left the flex plate lose when they replaced the engine?

Have them look at that balancer again... Up close and personal too..

Read your first post-I've had bad harmonic balancers, bad flexplates & bad trans, albeit on different vehicles but none had lack of power & had to limp home like you mentioned. I even had a broken rocker & it made a terrible racket but I was able to drive home under good power (V-8).

Hard to guess what the problem is but I would look at power output, so if it isn't the engine itself it might be in a sensor, black box, etc. Since the engine was replaced with used from unknown source, the electronics, if changed, might not be 100% compatible & possibly something isn't hooked up, or is hooked up wrong, or is the wrong application?

If the dealer can't definitively identify the problem, meaning they'll do something but it isn't the root cause, I would look for another vehicle.