I've gone through 5 motors in the past 8 years...each of them a junkyard motor w/ over 150,000 miles on em. If that wrist pin seemed kinda loose, that could be your noise. If you change one out, might as well do all 4.

 

I'm pretty sure I can take the pistons out the bottom. Can I put em back in the bottom? I don't want to take the head off if I don't have to.

 

nope you would have to pull the trans and crank to pull the pistons out of the bottom. since you have it tore down that far might as well do the head gasket water pump and timing belt if it has over 105,000 miles and are not sure when they were replaced.

 

no, you won't be able to get them back in the bottom, even if you pull the crank...a piston ring compressor doesn't work that way...has to be the flat surface where the head meets the block.