Starter is slowly turning over on a rebuilt engine.
Just rebuilt the engine on a 1977 MGB. Tried starting the engine and it will slowly turn over. Checked the battery and it is fully charged. The ground strap from the engine to the frame has been connected.
Did you ensure the engine would turn over by hand prior to installation? It is possible that you overtightened the main bearings, which should be set at 70lb.ft. If you are sure that is not the case you could try and remove the spark plugs to see if the starter will crank faster without compression. If it does turn over a bit quicker then it's either a bad battery or a starter motor. Put back the spark plugs and check the voltage on the starter motor to ensure the battery is providing enough power to the starter. Anything under 10 volts means your battery isn't up to the task anymore and needs replacement, it might seem fully charged but may not provide the power it did when it was new.