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Piston numbers

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    Senior Member SBS933's Avatar
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    Default Piston numbers

    After tearing off the heads to have them freshened up, I noticed numbers stamped on the pistons. I was told by the previous and original owner that the motor was balanced and dyno'd. It does have all the dyno hook-ups on it so i never doubted him. He told me not to touch anything, just keep up the maintenance. Someone told me the numbers were how many grams were ground off that piston so they would be the same weight. Is this true ?

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    gn7
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    Quote Originally Posted by SBS933 View Post
    After tearing off the heads to have them freshened up, I noticed numbers stamped on the pistons. I was told by the previous and original owner that the motor was balanced and dyno'd. It does have all the dyno hook-ups on it so i never doubted him. He told me not to touch anything, just keep up the maintenance. Someone told me the numbers were how many grams were ground off that piston so they would be the same weight. Is this true ?
    Thats BS. No body writes the number of grams removed from anything. Its useless information. If there is anything written on a part its the actual weight after balancing. Usually done with an eletric pencil on the under side, not the top. You're looking at a part number or somethng similar.

    What do "dyno hook ups" look like? Never seen them, and I have had a motor or two dyno'd.



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    Senior Member riverslide's Avatar
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    Quote Originally Posted by gn7 View Post
    Thats BS. No body writes the number of grams removed from anything. Its useless information. If there is anything written on a part its the actual weight after balancing. Usually done with an eletric pencil on the under side, not the top. You're looking at a part number or somethng similar.

    What do "dyno hook ups" look like? Never seen them, and I have had a motor or two dyno'd.
    Very true... I spent a few years with Louie Unser & Bud Gilbert. I would check out the hole motor after that BS....

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    Senior Member SBS933's Avatar
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    Quote Originally Posted by gn7 View Post
    Thats BS. No body writes the number of grams removed from anything. Its useless information. If there is anything written on a part its the actual weight after balancing. Usually done with an eletric pencil on the under side, not the top. You're looking at a part number or somethng similar.

    What do "dyno hook ups" look like? Never seen them, and I have had a motor or two dyno'd.
    I will post a pic of one of the pistons later, the numbers are actually stamped in on the topside of the pistons, a neighbor told me it was for grams taken off. The dyno hook ups were just temp sensing wires on the exhaust ,and the other one i got rid of awhile back, i don't even remember were it hooked up too.

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    Senior Member SBS933's Avatar
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    Quote Originally Posted by gn7 View Post
    Thats BS. No body writes the number of grams removed from anything. Its useless information. If there is anything written on a part its the actual weight after balancing. Usually done with an eletric pencil on the under side, not the top. You're looking at a part number or somethng similar.

    What do "dyno hook ups" look like? Never seen them, and I have had a motor or two dyno'd.
    here is a pic
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    Last edited by SBS933; 09-10-2012 at 04:38 PM.

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    Quote Originally Posted by SBS933 View Post
    here is a pic
    Nope. No pic. Numbers stamped in the top of the piston are usually part numbers. Your friend doesn't sound like he knows what he's talking about.
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    Senior Member Ronboats's Avatar
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    Maybe the oversize? .030-.060 etc.?

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    Senior Member Spike Morelli's Avatar
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    Default Numbers on piston tops

    I concur with any number likely being possibly a part number, sometimes an over size, but never anything to do with final balance or how much may have been removed. Final balance weight recording should be on a balance card, which is filled out by the shop performing the balance job.
    I work at Valley Head Service, and we do balancing. The tech who does this job records all of the pertinent weights on this card, prior to attaching the "bob weights" to balance the crank. After the job is done, WE keep a copy of the balance card, job number and information, and the CUSTOMER gets the original balance card. That's where your piston weights should be.

    Which brings up a related issue......Every single one of you out there who is building an engine, or is/has had an engine built for you, should have and keep a folder on your engine. Keep every receipt, bill, service done, part numbers,cam card, special torque info i.e.head stud torque, rod and main torques, balance information, whatever. If you bought a boat from another party and therefore, don't have this info, well, I can believe this happens, but ASK FOR IT! Be professional. Let's say you kiss a piston with a valve, and need to replace any components, if you keep records, you can order a replacement part and have it balanced to match the rest. You may never need this information, but "stuff', happens doesn't it?
    Last edited by Spike Morelli; 09-09-2012 at 09:59 PM.

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    steelcomp was here
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    Quote Originally Posted by Ronboats View Post
    Maybe the oversize? .030-.060 etc.?
    Could be that too.
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    Default Factory oversize...???

    Quote Originally Posted by steelcomp View Post
    Could be that too.
    Looks like the factory oversize numbers from the 327 SBC era. It wasn't uncommon to get an engine with 8 different size bores....And those were neatly stamped in the tops of the pistons... They weren't nearly that big, but I know that isn't cylinder #9 in the pictures...

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    gn7
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    like I told the OP in a PM. If it was the grams removed, one piston wouldn't have a number.



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    Quote Originally Posted by gn7 View Post
    Thats BS. No body writes the number of grams removed from anything. Its useless information. If there is anything written on a part its the actual weight after balancing. Usually done with an eletric pencil on the under side, not the top. You're looking at a part number or somethng similar.

    What do "dyno hook ups" look like? Never seen them, and I have had a motor or two dyno'd.
    I have a Dyno and I have no idea what he is talking about????

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