We have a stock ap1 rebuild going on. We had to get it re sleeved with non frm sleeves, we are putting back the standard OEM pistons. Which rings should we use? The other threads I've seen didn't address this issue directly. Thanks

 

I dont think you can use stock oem pistons with iron sleeves. However you can order new aftermarket pistons than come with appropriate piston rings and be set
http://realstreetperformance.com/sto...your-block-55/

Pick whichever one you like that fits your build needs, I personally would go for the JE or CP set-up

 

Thx man good to know, not many people knew that about the stock pistons.

 

you could use stock pistons back in a sleeved block, but that's not ideal lol.. It might not be reliable but shops do it all the time when they mess up on slight bores. I knew a shop back home that missed the 0.25mm oversize and resleeved AEBS for the customer free of charge, then ran it fine.

 

FRM sleeves are super tricky to get right...damn this precise motor

 

The machine shop didn't want to bore the FRM sleeves, thats why they re sleeved it with regular sleeves back to standard bore. Is there danger in running the pistons for the frm cylinders in NON-FRM cylinders? Thanks for the help guys.

 

This will NOT WORK.

 

Just get some CP pistons, they're much better anyway. Frm pistons should not be used inside of iron sleeves.

 

What this guy said. I was to lazy to type that out.

 

Either of you guys try it? If not, should probably look into it more.. lol you can't use forged pistons in FRM sleeves reliably, but the other way around what's the issue? The pistons aren't FRM pistons, they're made for cylinders with FRM walls. The pistons are a certain alloy (i'm unsure of) but they shouldn't be anything exotic with a crazy expansion rate..

Edit: the only thing I would be most concerned with is the rings since those are designed for FRM

 

The stock pistons are also FRM coated, not the best choice when using aftermarket sleeves. If it's going to be apart for the resleeving, why not put better, stronger pistons in there...

I can also see the stock rings being a problem as well.

 

Thats what i wasn't sure of thank you sir.

 

Bump

Can anyone explain (with science) WHY pistons from a FRM block cannot be used with iron sleeves?

Does it cause the same damage seen when using aftermarket pistons with FRM?

 

Most likely not, if there is a problem with FRM pistons + ductile sleeves, it would be excessive blowby or rings not sealing properly.

The problem with FRM sleeves + forged pistons to my understanding is the expansion/contraction rate differences between the two. But ductile iron sleeves shouldn't get scarred by FRM-compatible pistons because ductile iron is a sturdier material.

This is all speculative, I would personally shell out the 4-700$ on pistons just to not second guess myself.

 

But to my understanding the pistons designed for frm sleeves are actually an aluminum with a steel coating on the skirts. Can anyone confirm this

 

I coincidentally just came across the situation discussed. You CAN use OEM pistons with iron sleeves without catastrophic engine failure. I just opened up my spare motor and it has 1 cylinder that's sleeved with an iron liner. The cross hatches and wear looks better than stock actually and there are no abnormalities. This engine was run this way for over 15k before the car was wrecked.

 

Are you going file-to-fit?