Not an run.
The balancer is an outer/ inner ring put together with rubber, so the TIMING MARK can slip. This has nothing to do with the engine running, that is, if you get the engine running, and the timing mark slips, the engine will still run until the next time you try to check timing and then it will be way off.
So for your problem
1---The cam may be out of time, IE a worn timing chain/ sprocket.
2--You could be misinterpreting what it is that is happening
3--Part of this is that the timing mark has slipped, "maybe," but that does not explain how you were able to time it in the first place.
YOU DO KNOW how Mopar cylinders are numbered? We are not working on a Ford here, IE no 1 on a Mopar is no5 on a Ferd
1--Get yourself a piston stop and check the timing marks for accurate
2--Run a compression check, or try to find out the specs on your cam, and try to determine if the cam is in time. By marking some degree marks on the balancer, and watching the valves, this is possible.
3--Recheck the distributor setup AFTER making sure the timing mark is OK. Pull no1 plug, stick your finger in, and feel for the START of compression. Then watch the timing marks, and bring the marks up NOT to TDC, but where it is that you want initial timing, IE about 12-15* BTC.
Then confirm that WHEREVER the rotor points, that is where the no1 plug wire lines up.
Also grab the rotor and give it a good firm twist, maybe the cheap *** distributor ?? you have?? has come apart "up top." I've seen this happen on GM V8 distributors, twice in my life.
