i had that problem a year or so ago , but i don't want to curse anyone by saying big end .. so i wont
, id get a compression test if you are worried and find out before you really fuck something. but i also get a quick rattle around the 3k mark still when its cold , ASG think it is the heads and said it didn't get shimmed properly when it was re built , not a problem dow.
but yer , get a compression test if you think its a big end and good luck