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Jahns pistons

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Woosterkevin View Drop Down
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    Posted: Sep/13/2016 at 4:14pm
Can anyone identity these Jahns pistons? I know they are .30 over by measuring and the faint Jahns name on the underside.I removed them from my 360 that I believe was rebuilt in the late 80's. I want to reuse them in my new 360 build but would like to find out a little more about them if possible.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401jim Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 4:21pm
Need more pictures of the bottom. Also the top please......
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Woosterkevin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 4:45pm
I am trying to get more uploaded thanks.
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shootist View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 5:49pm
The look to be forged but hard to tell without seeing the underside. If they are not damaged you can reuse and you can use a syringe and flat piece of plexi glass to get a read on the dish CC. On the surface from the one pic they look like a pretty nice piston. Even if they are cast you could still reuse them without much issue provided they are not damaged. Look at the top ring lands and make sure they are not lifting (very uncommon in an AMC motor common to a Pontiac).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 5:56pm
Oh, I would like to add that if you are not supercharging or spraying with NOS cast is more than adequate. Forged is nice for performance just to be more resistant to detonation but aside from that you still have a cast crank in the 360 which is the weakest link and limits any build to 500-600 HP before the life expectancy will drastically begin to fall off.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 6:04pm
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Woosterkevin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 6:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 6:31pm
Not planning on supercharging or spraying, I just want a nice performance driver. Something that i can drive everyday if i want, but also get up and go when some tuner thinks he is king i can knock off his crown lol.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 7:37pm
Well that is a dome piston. Still need to see the underside where the connecting rod goes in to figure out if it is forged but if you are not going huge power I would not be worried. If you look up in where the wrist pin is and it has cross hatching then it is definitely cast. This is usually the only place to tell if it is cast vs. forged. A forged will never have the cross hatching there internally but even a cast piston could have them removed. However, there would very few people (if any) that would want to perform custom machining on a cast piston because it is still just a cast piston. If anything you will need to watch your valve clearances if using that piston since it will go up into the combustion chamber as it is. Do you have the heads that were used with the previous build? I would ensure that you look them over closely and ensure whatever heads you decide to use have the same clearances.

Edited for literacy issues. I cannot think, I has the beer.


Edited by shootist - Sep/13/2016 at 7:41pm
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Woosterkevin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/13/2016 at 7:42pm
I will stop by the machine shop and get a pic of the underside. I do have the heads but they have pitting on the valves and seats so they would need totally reworked to use them.
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