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Re: i posted that the ones sold by F/M are
Mike and clem-----
Yes, that's what I was kind of getting at earlier. The change in part number may be an indication that these SERVICE pistons are manufactured of a different material than the originals. That could be ONE reason why the part number changed. I think that Federal-Mogul may be pretty much out of the conventional alloy, cast piston manufacturing business; most, if not all, of their stuff is probably hypereutectic alloy by now.
The numbers that you have described that were found do not look like either Federal Mogul or GM numbers. So, I tend to think that these pistons were not manufactured by either F-M or the GM Powertrain Bedford, IN foundry (which used to and/or still does cast-up many GM pistons; these pistons are finish-machined at the GM engine plants for PRODUCTION or SERVICE).
So, it may be that these pistons are manufactured by some entity other than F-M or GM Powertrain. In that case, I have no way of knowing what the manufacturing source OR the material is. There may be other piston manufacturers out there that do still make conventional alloy, cast pistons.
Actually, if you want to ensure that you get hypereutectic alloy cast pistons, which I highly recommend for ALL street applications, then I'd recommend that you just buy those and skip the GM pistons. I can virtually guarantee you that the GM SERVICE pistons currently available are not of internal GM manufacture, either with respect to casting or machining. So, what you're probably getting is an aftermarket-type piston in a GM box. I'm not saying that these are bad pistons; I'm sure they're quite good. However, there is some uncertainty as to their material and I don't know how to get a straight answer out of GM on an issue like this.
Federal-Mogul or Keith Black/Silvolite hypereutectic cast pistons are readily available and are not hugely expensive. These are very high quality pieces. I'd say that they are as good or better than the GM SERVICE pistons available today for old applications.
Mike and clem-----
Yes, that's what I was kind of getting at earlier. The change in part number may be an indication that these SERVICE pistons are manufactured of a different material than the originals. That could be ONE reason why the part number changed. I think that Federal-Mogul may be pretty much out of the conventional alloy, cast piston manufacturing business; most, if not all, of their stuff is probably hypereutectic alloy by now.
The numbers that you have described that were found do not look like either Federal Mogul or GM numbers. So, I tend to think that these pistons were not manufactured by either F-M or the GM Powertrain Bedford, IN foundry (which used to and/or still does cast-up many GM pistons; these pistons are finish-machined at the GM engine plants for PRODUCTION or SERVICE).
So, it may be that these pistons are manufactured by some entity other than F-M or GM Powertrain. In that case, I have no way of knowing what the manufacturing source OR the material is. There may be other piston manufacturers out there that do still make conventional alloy, cast pistons.
Actually, if you want to ensure that you get hypereutectic alloy cast pistons, which I highly recommend for ALL street applications, then I'd recommend that you just buy those and skip the GM pistons. I can virtually guarantee you that the GM SERVICE pistons currently available are not of internal GM manufacture, either with respect to casting or machining. So, what you're probably getting is an aftermarket-type piston in a GM box. I'm not saying that these are bad pistons; I'm sure they're quite good. However, there is some uncertainty as to their material and I don't know how to get a straight answer out of GM on an issue like this.
Federal-Mogul or Keith Black/Silvolite hypereutectic cast pistons are readily available and are not hugely expensive. These are very high quality pieces. I'd say that they are as good or better than the GM SERVICE pistons available today for old applications.
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