Spark plug gap closing???

[sc racing]

What could cause the gap to close up by about .010?? This is just a 260hp 350 GM crate engine brand new with a few hundred miles, still had points ignition gapped plugs at .035 then changed to electronic went to gap plugs to .045 and they were all about .025???? There is no obvious marks from contact between the ground strap and the piston I dont even see how thats possible with this engine. Stock style pre 1986 heads 76cc chamber probably a 4 valve relief dish piston and #25 autolite plug.
Any thoughts?
Thanks

[want-a-be]

Lean??

[sc racing]

Thats what I was thinking (getting hot) he's been trying to get through emmisions by retarding timing and leaning out the mixture. I thought I was going seing things I know my glasses work i just went to the eye doctor!