HELP! I Dropped a Piston!!!!

[Rot 911]

Don't ask me how. I already feel incredibly stupid. Not to mention sick to my stomach. I dropped one of my pistons on the concrete garage floor and of course it hit on the weakest spot, the piston skirt. As you can see from the pictures I have a crack all the way through the skirt and the corner of the skirt is bent. The question is what are my options? Can I buy just a single piston or do I have to buy a piston and cylinder together. Damn! Damn! Damn my stupidity! I am cross posting this to the Tech and Engine Rebuild Boards to get as many good opinions as possible.

[Tyson Schmidt]

Well, that's obviously a used piston, so if I were you I'd look for another used piston from a dismantler, or private party. Measure the ring lands and determine what thickness the rings are so can find a matching piston.

Then, once you find a matching piston, get a gram scale and slide the wrist pins in each of the pistons. Then weigh them all, and if you find a heavy one, remove material from the wrist pin until they all match perfectly.

[Rot 911]

Tyson, thanks for the advice. But I have a couple of questions. First why would I need to measure the ring lands? Aren't all U.S. 3.2 pistons the same? Second, I like the idea of having all pistons weighing the same. Where would I remove the material from the wrist pin? I am assuming from inside the hole that runs through the pin, but I know what happends when I assume.

[Tyson Schmidt]

Originally posted by Kurt V
Tyson, thanks for the advice. But I have a couple of questions. First why would I need to measure the ring lands? Aren't all U.S. 3.2 pistons the same? Second, I like the idea of having all pistons weighing the same. Where would I remove the material from the wrist pin? I am assuming from inside the hole that runs through the pin, but I know what happends when I assume.

Well, I had no idea what engine you are building. That's why I recommended measuring the ring lands. Early cars came with varying dimensions.

You should remove material from the inside bore of the wrist pin until it matches. Preferably from both ends equally.

I had to replace one piston during my rebuild, and the one I found was quite a bit heavier than the others. Even with the lightest wrist pin installed in it, I had to grind down the wrist pin quite a bit. It sure is a smooth running engine now. Those little attentions to detail make all the difference. Particularly on an engine like mine that spends quite a bit of time over 7000 rpm.

[Wayne 962]

Originally posted by Tyson Schmidt
Then, once you find a matching piston, get a gram scale and slide the wrist pins in each of the pistons. Then weigh them all, and if you find a heavy one, remove material from the wrist pin until they all match perfectly.

Or, mix and match the heavy pistons with the lighter wrist pins. You can usually get very close with this approach (that's a tip from Walt at Competition Engineering)...

-Wayne

[john walker's workshop]

i probably have a used one.