410 six pack crate engine

It appears to not be getting spark all the time.

It has all the MP stuff....distributor and orange box etc..

Just tried to start it and it appears to only get spark when I stop turning it over and let off the ignition.

I have heard a lot about bad luck with these orange boxes.

I have had it running by the way and the first day it ran great. Tonight it started right up and drove it a little bit and then went to start it 1/2 hour later and it cranked over but wouldn't fire and that's when I found it had no spark. It seems to come and go...maybe once it gets warmed up?

Any ideas?

Thanks.