puzzler for ya

I pick'd this 68 cuda with a 76 360 up last April. You all are starting to know that I'm learning as I go. (thanks for your patients) About a month into it I take it down the road and decide to give it some gas, OK all it would take! and I thought it jumped time. Limped home and found a little carbon on the rotor and the No. 2 spark plug gap was closed. ?? Yesterday I finish putting in a new distributor and ECU. Took it out to time it up (by ear) tonight. It's starting to run good right. Put the vac line it's going well. Then I decide to let it go to 5000 and then it runs like crap !!!!?? turn it off back the vacume down 180 and no change. Bring it home and guess what that No. 2 plug gap is closed up again. I notice it's got a tiiny little nick on the tab at the bend on the side really. It's only the one plug.

what the h&!! is smacking that spark plug?? thanks in advance!

lap