alright i have a question that maybe some one could help me with. i am going to rebuild my 5sfe engine and i have a set of 40 pistons for a 7afe laying around. they are brand new with the wrist pins and rings. could i use these on my 5sfe engine if i gave the pistons to the machine shop and told them this is whats going in. any help would be great. thanks

i highly doubt it. the 7a has narrower cylinders than the 5s (someone correct me if I'm wrong)

.40 over will make the walls a bit narrower, but its something that has been done before. My buddies patiently collecting parts for his ultimate 5sfte built. Wiseco 88.0mm pistons.

I know the walls will be a bit narrower but after this build I don't plan on rebuilding again. If these pistons will work then it will save me some money and get my build a little closer to finish. I'm not going to be turboing or anything crazy. Just looking to make it a reliable car for my wife to drive. I'm picking up a motor that runs with 165k miles and it's knocking in the bottom end for 100 bucks. So I figured I would drop her off at the shop to get the cylinders bored and honed put in some new rods and mains and ur normal timing belt water pump oil pump and valve stem seals. If these pistons will work then I would say it's a go.

7A-FE pistons in a 5S-FE won't work since they are 81mm in diameter and the 5S-FE got a 87mm bore.

Is that stock pistons size? Like I said the pistons I have are 40 over. If there bigger then the stock 5s pistons then they should be able to bore the cylinder to make them fit, correct?

no.

they're not bigger than the 5s because the 7a cylinders are narrower. If the 7a is 81mm and the pistons are 40 over, that means they are 81.4mm, not 85mm. The 5s has a 87mm bore. If you look in the stickies it would tell you.
You can't hone the 5s an expect it to become smaller...

K I see what ur saying now. Thanks. And merry Christmas.

thats only the first problem, there is also wrist pin location and diameter. i highly doubt the 7A pistons will fit on 5S rods.