Hey sepp,
Here is my amateur stovebolt engine input opinion. I just rebuilt my first 235 a few months ago and its the first engine I have ever done. If you have the time and space permitting since you are in Germany, after you do the test that Pre 68' Dave explained and you confirm that it is a bad rod bearing why not replace it yourself? If everything else is ok such as compression, the head, oil pressure etc. then I would keep what you have and do it yourself.
If you crank is scored you can have it checked and turned down then replace the bearings. Most of the motors I see for sale usually needs to be rebuilt and if they are rebuild they are wanting between 2k - 3k. A while back Tom from Stovebolt Engine Company had a 261 rebuilt for sale, when I was searching but I decided to do my own 235 rebuild with the upgrades I wanted (intakes, carbs and cam) and it cost me about 3500 USD just for parts and machine work. Seeing how easy everything was in those motors just pricy for parts, I would do the repair on what you have since you know everything is original and you know what you have. Plus if you decided to upgrade anything such as cam or what ever you can do it then. It might be a good time to give it new rings also.
I guess the first thing is to verify the where and what the noise is. I guess is what I am trying to say is if you are going to replace the motor you have to pull it out anyway. If you are going to pull it out why not drop the pan and check it out it might be a whole lot cheaper to repair than getting a reconditioned one. Plus now you have to worry about what the other guy did or did not do.
Just check out the simple things first before you do a major job.
good luck
Last edited by Tiny_Jaime; 07/05/2013 10:43 PM.
"As I lay rubber down the street, I pray for traction I can keep, but if I spin and begin to slide, please dear God protect my sweet ride." -Amen
56 Chevy 3100