Critical piston question
Thread Starter
Le Mans Master
Joined: Nov 2004
Posts: 6,128
Likes: 21
From: North Alabama
Critical piston question
While tearing down my 350 for a top end rebuild I found a small ear off one of the bottoms of the pistons where it appears it came off during assembly. The motor was strong before disassembly before tearing it down with no noise and compression in all cylinders were consistant.
The motor was stated as having roughly 10,000 miles on it when I purchased it. My question is "what if anything will this affect"? Balance? There is no indication of any scoring of the cylinder wall in which it came from. Any help or suggestions would be appreciated. Major concern? Minor concern? No concern?
The motor was stated as having roughly 10,000 miles on it when I purchased it. My question is "what if anything will this affect"? Balance? There is no indication of any scoring of the cylinder wall in which it came from. Any help or suggestions would be appreciated. Major concern? Minor concern? No concern?
Burning Brakes
Joined: Feb 2004
Posts: 758
Likes: 14
From: Ville de la Baie Quebec. A winner is just a loser who tried again.
The local performance machine shop here, balances pistons to within 4 grams. So if you can guestemate the weight of the missing peice to be within this range,, I don't think it be a problem.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Michel B
The local performance machine shop here, balances pistons to within 4 grams. So if you can guestemate the weight of the missing peice to be within this range,, I don't think it be a problem.
why not take it to a machne shop and get their opinion....can you post a picture of it? some of the lower piston skirt area is used to stop the piston from rocking in the cylinders...its hard to tell you anything definitely with out pictures......but if it was running well before hand and there is no scoring i would say these are positive signs...
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Jclgodale3
added it to my photo's if you don't mind taking a look?
can't find it ....can you see it in your gallery?
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Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
Where did you find the piece, in the oil pan? Is it a cast or forged piston? Are you sure it has been off since assembly? They are there to keep the piston from rocking, and the cylinder should have weird wear marks on it if it was missing for long. .
BTW, I dropped one of my pistons when tearing it down for new bearings, and broke the same piece off. The machine shop that did the rods got me a replacement for not much money.
Joe
BTW, I dropped one of my pistons when tearing it down for new bearings, and broke the same piece off. The machine shop that did the rods got me a replacement for not much money.
Joe
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
NOt sure what to do there maybe talk to a machine shop about it, possibley if you know what the part number of that piston is you could replace it re-using the broken in rings. Any half decnet piston set is weight matched these days so the wieght would probably be OK if it was the same part number. Not sure but that piston could damage the cylinder so you have to tear it down anyway and it could even gouge it meaning a new block 
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
thats pretty big.........it looks like it is the part of the piston skirt that stops the rocking motion....if you want my opinion i'd say that piston is toast.........i could not justify putting that back in.... a picture of the piston would confirm my thoughts... sorry...i know you are having difficulites posting them....
Burning Brakes
Joined: Feb 2004
Posts: 758
Likes: 14
From: Ville de la Baie Quebec. A winner is just a loser who tried again.
You know,, I broke a peice off one of my pistons by hammering them out with a wooden dowel, and before anybody says that I must have hammered the crap out of it,,,(I didn't). they are suprisingly delicate. You know, I think we are all alike in the sense that we want to save a few bucks when we can,, and thats ok, but for the price of a new set of pistons (stock),, I think it would be wize to change them. Once the motor is all back together and in the car, you will hate yourself if it develops a vibration... 
Advanced
Joined: Jun 2004
Posts: 52
Likes: 0
From: Ventura County ca
My vote would be fix it. You already have it apart so it's no big deal. It would suck to put it back together and have a vibration or worse have it shatter the piston down the road and ruin the crank/block/heads/cam/etc. Who knows what the rest of the piston looks like or if it has any cracks in it that you may not be able to see with the naked eye from underneath looking up. A few dollars is cheap insurance and piece of mind.
