Auto Parts: 4.3L V6 Vibration, o reily, engine vibration

Question
I have a 1990 Chevy G-20 Van I recently replaced the engine with a rebuilt 4.3L V6 bought from O'reily's Auto parts it ran rough from day one but now its two years later and i have a major vibration i have replaced the harmonic balancer and flex plate and vibration still exists it has broken a water pump pulley and power steering pump bracket I would like to know what the problem may be and also can an internally balanced crank become unbalanced?

Answer
Hi C.J.,

An internal engine vibration is a good indication that the assembly is on it's way out. I'd bet that if you pull the pan off you'll find a few piston skirts laying in the pan. You should have pulled and sent the engine back when you noticed it was vibrating right-out-the-box.

Just for sh!ts-n-giggles, I'd do a compression test and see if one of the cylinders is dead. If a compression test yields consistent results, then I'd have to guess that something internal, yet not vital, broke.

Thanks for the question, I hope this information was helpful to you.
Fred
www.knucklebusters.us
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