Piston Skirt Abrasion

[85rkyboby]

Hey all,
I got some pistons here from a buddies build. He has minor abrasions on his piston's skirt from the main bearings. He's wondering if they are still useable? I can't feel any grooves on the piston but you can definitely see it.
Thanks!

 

[85rkyboby]

@84Ttop @RacEoHolic330 @Noobz347 @A5literMan @srtthis

 

[RacEoHolic330]

I'll let some other guys comment on this one. I do know that mine were way worse though.

 

[85rkyboby]

@RacEoHolic330 Wow. I think I remember you posting that a little while back, Did you end up going with new pistons?

 

[85rkyboby]

Nevermind, I back tracked through your build thread.

 

[84Ttop]

Hey all,
I got some pistons here from a buddies build. He has minor abrasions on his piston's skirt from the main bearings. He's wondering if they are still useable? I can't feel any grooves on the piston but you can definitely see it.
Thanks!

Those pistons don't look to be in too bad of shape. Depending on the application and what pistons they are would depend on me recommending re using them or not. Wear like that can be caused by a few different things, lack of lubrication on the cylinder walls (improper hone, glazed walls, too much oil ring tension) or they could not be sized properly for the bore. A bad main bearing typically won't affect the pistons unless a bunch of metal gets up in the cylinder walls and tears them up.

Scott's pistons are a whole different deal and in my book are a conversation piece at this point

 

[85rkyboby]

@84Ttop Thanks for the reply Nick. These are the 4340 (not sure if that's the right series) forged pistons going in a high boost (20-25 psi) application. Small motor 1.8 to be exact. The pistons are JE Brand

 

[84Ttop]

@85rkyboby If it's an off the shelf piston and it plans on seeing 25lbs of boost it might not be a bad idea to grab a new set (especially if you only need 4) They could surely be re used but something making a lot of power I might save them for spares. Something else to consider is wrist pins... ask me what I know about wrist pins and a lot of boost... lol

 

[A5literMan]

The piston wear doesn't look horrible to me. But...20+ lbs of boost and a small motor sounds like a high rpm and cyl pressure combo. Have you had them mic'd? I'd probably run them but I would be slightly concerened. They should be fine though.

 

[85rkyboby]

@85rkyboby If it's an off the shelf piston and it plans on seeing 25lbs of boost it might not be a bad idea to grab a new set (especially if you only need 4) They could surely be re used but something making a lot of power I might save them for spares. Something else to consider is wrist pins... ask me what I know about wrist pins and a lot of boost... lol

What should he worry about the wrist pins, if you don't mind going into a bit of detail.

The piston wear doesn't look horrible to me. But...20+ lbs of boost and a small motor sounds like a high rpm and cyl pressure combo. Have you had them mic'd? I'd probably run them but I would be slightly concerened. They should be fine though.

We are currently trying to mic the pistons. We don't want to be even slightly concerned with the build. As y'all have stated high boost in a tiny motor. We are shooting for 400-ish HP with boost.

 

[84Ttop]

What should he worry about the wrist pins, if you don't mind going into a bit of detail.

We are currently trying to mic the pistons. We don't want to be even slightly concerned with the build. As y'all have stated high boost in a tiny motor. We are shooting for 400-ish HP with boost.

If you want to eliminate the concern then order new pistons.. It's not out of the realm of possibility to destroy one and need a spare some day so save those for a bad day.

With a lot of boost, I worry about wrist pin wall thickness. Most standard wrist pins can not take the abuse of that kind of cylinder pressure and need to be upgraded. When ordering off the shelf pistons you get off the shelf wrist pins. Call JE direct and ask for wristpins that are more suited for your application. A few years ago: 5 broken wrist pins, 5 broken pistons, 5 destroyed rods and a cylinder head with a hole melted out the side of it later I learned my lesson

 

[85rkyboby]

Sounds like a superb idea! We'll save those for the storm.

We'll give JE a call. Sounds like another expensive lesson my friend. I can't wait!

 

[srtthis]

me personally i wouldnt use them. i have a "bad" piston on my desk at work from the nitrous motor and it looks a lot better than that