040 Stamped on pistons.

[1984ranger28]

Hi, im currently rebuilding my 2.8 and all 6 pistons have 040 stamped on them. Im assuming this means its been bored 40 over, but wanted to make sure before I order rings. Thanks, Lucas.

 

[alwaysFlOoReD]

That would be what I would think too. But to be sure you need to measure the bore. At the same time you can make sure it doesn't need another bore job.

 

[1984ranger28]

Alright, thanks for the response.

 

[enginepaul]

That's .40 over. As said before MEASURE before you order anything. My experience is that there is very little bore wear in these engines but double check.
The .40 over, I'm sure, wasn't from ordinary wear.

 

[1984ranger28]

What would be the max bore wear before you couldn't hone and re ring?

 

[alwaysFlOoReD]

That really depends on engine design. I'm not familiar with the 2.8. I have a 283 that's bored out 60 over and apparently can go to 120.
Best is to talk to your machine shop, they would likely have the knowledge as long as they aren't all under 30 years old.

 

[fastpakr]

I think the OP was asking about allowable taper before having to overbore. As far as that goes, I think you'd have to look that up somewhere. A decent machine shop doing the work to clean and measure everything on the block would certainly have that information.

 

[alwaysFlOoReD]

IIRC, On a 429/460 allowable taper is .004. I was going to rering at .007 but never got there to test. I don't know for the 2.8. Unless you have several hundreds of $ in measuring tools a machine shop is going to be your best bet.

 

[1984ranger28]

Update: I got my 40 over pistons today, and they fit perfectly. However, I did measure the old pistons and they were stock. Which explains the heavy scoring and material loss in every one lol.

And yes, those are all different pistons

 

[Uncle Gump]

I'm a little confused...

Someone put stock pistons in a block bored 0.040 over?

 

[fastpakr]

-And- labeled them 040? Something doesn't add up.

 

[Uncle Gump]

I agree...

Those pistons are tore up! Lots of metal transfer... the bore certainly had to be torn up also.

 

[fastpakr]

How does the bore look?

 

[Uncle Gump]

fastpakr... I will just answer that one.

The block needs to be bored but now my new 0.040 over pistons won't fit.

@1984ranger28... take a deep breath. You seriously need to get that block to a machine shop and have it looked at. My experience says that a hone job won't fix it and you will probably have it back apart in short order.

 

[fastpakr]

Agreed 100% on getting it to a machine shop. Recipe for pain and suffering otherwise.