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390 Piston weight
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amxron View Drop Down
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    Posted: Oct/22/2021 at 10:04pm
Anyone know what the weight of a stock 1970 390 piston is?

Ron.
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Points: 6881 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Oct/23/2021 at 9:13am
Can get you close:
TWR forged were 572g and KB hyper are 532g.
Stock were 564g as memory serves. Hopefully some one has one on a shelf that can get an actual number.
AMC pin weights are something you really need to consider. They went from 85g to 110g on 401's. Don't know the 390 AMC's, but NHRA states 90g for race rules for the 390.
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Points: 295 		Post Options Post Options   Thanks (0) Thanks(0)   Quote amxron Quote  Post ReplyReply Direct Link To This Post Posted: Oct/29/2021 at 1:32am
Thanks Trader, I had forgotten about the NHRA listings.

Ron.
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Points: 969 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Class Guy Quote  Post ReplyReply Direct Link To This Post Posted: Oct/29/2021 at 6:52am
NHRA specifications can sometimes be manipulated to accommodate available parts and/or racers' influence when it comes to piston and rod weight.  For example, the minimum weight for any AMC V8 rod 573 grams, which is way light for OEM parts.  However, that allows the use of aftermarket Chevy 5.85" Manley rods which were also approved as replacements.  Just saying that you should do some more research.

The 1970 AMA documentation lists the 1970 390 piston at 21.94 oz., which is 622 grams.  That probably includes the weight of the pin, since the section on the pin data does not include weight.
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