Distributor jumping time.

[ecbach82]

So i recently bought a dohc engine. It was a donor motor because i was desperate. fast forward. I couldn't get it to start. fixed lots of problems thinking they were the cause for it not starting. Then while checking the timing i realized the distributor was jumping time. The donor motor looks like it has a new head and double roller chains. Is there a change that should have been made to distributor gear or something else to check?

Just an example is I got the motor to fire just after checking timing. then after charging battery it had jumped 180 degrees. dont know?