Car Repair

I have to replace my block heater with a round steel plug. i have tried a thing: tapping it, gently hammering it but it seems like its slightly too big even though the auto parts guy assures me its the right size. any suggestions?

Freeze it. stick the plug in your freezer for a few hours and then try to install it. the cold will cause the steel plug to shrink a little and you may be able to get it in better. nice luck, hope this helps.