pulled my motor down today and found this, talked to my local machine shop and they told me this was very common in stroker motors with this size skirt. what are my options? can I reuse them? should I look for a smaller skirt piston?

 

not sure how many short skirt pistons are avalible for us FI guys

 

I think part of the problem with strokers is the piston is very short because of the stroke.

I was also told by a machinist that a bad tune up and detonation can cause where like that and collapse the skirts (I had collapsed the skirts on a couple pistons in my old motor)

 

Wondering if I should reuse them

 

they look like these?

 

My 404 used to do this real bad. The stroke pulls the piston out of the bottom of the bore too far.

 

probably no. They should be measured to see if they had the skirt colapse. Looking the way they do I would think they are no good.

 

I'll Mic them up, should I run a short skirt piston?

 

Yes, normal for a 4" stroke in a short sleeve block. Do not reuse. Precisely why I am so against the 4" stroke.

 

my piston look that way do to the wrong piston to bore clearances

 

It can be helped with the proper piston to bore clearance, proper skirt taper, and finish on the bottom on the cylinder edge. Those skirts looks pretty torn up. I just had my motor apart with a 4" stroke setup and they actually looks pretty decent.

 

Think I'm at .005 clearance. Skirt taper is up to weisco. What piston should I look into.

 

actually that is not normal-got one here i just tore apart after 20,000 miles-no wear like that whatsoever.

 

what would be a guess of whats going on?

 

here is another pic without the flash glare

 

Is the bottom of the cylinder chamfered?

 

yes it is

 

how old are those pistons?

 

A skirt coating helps in addition to the other things mentioned. That is where GM went when they had skirt scuffing issues on the 3.4L (2.8) V6.

 

I have had good luck with Diamond pistons, maybe try a set of those on the setup and see if you have better results. I'd check the chamfer, and check piston to wall after the machine work is done.