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Jahns pistons

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pfordamx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pfordamx Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2016 at 9:24am
 with that dome i wonder what compression ratio will end up at. pump gas could be tough to run those pistons look like they should provide atleast 12 to 1
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2016 at 5:58pm
For what I can find on other forums Jahns made both cast and forged pistons, with both being heavy but of good quality. I was hoping someone in our AMC world had used these before and could give a little more information on compression ratio and cc. I do understand the pump gas and clearance issues. Onice I get the block bank from the machine shop and the pistons in I will measure clearance to be sure, but these were used in my old 360 with stock heads so I am pretty sure they will be fine and although it was late 80's early 90s when it was ruining, he used the cheapest gad he could find and claimed to have no issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2016 at 8:36am
Jahns forged pistons were made by what is now JE pistons> Yours look forged to me?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SKeown Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2016 at 12:33pm

 Info found on internet:
 
 "Jahns was a cast piston company (pretty rough too). Jahn Jr. wanted to get into the forging piston scene so they set up Jahns Engineering (later shortened to JE). This is were JE Pistons came from."

 "Most Jahns pistons were cast, and long have been. If the underside of the piston is rough with crosshatch markings, then it is cast. If it is smooth to the feel, with some striations visible, then it is forged. But I have never seen a forged Jahns piston. Jahns did once tell me that Ross will make forged pistons to Jahns specs, because they had an agreement."

 SKeown


Edited by SKeown - Sep/18/2016 at 12:43pm
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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/18/2016 at 2:56pm
Perhaps I am looking too critically, I could swear there appear to be very light parting lines present.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2016 at 4:17pm
It definitely looks like Jahns offered forged pistons for sale, but whether they actually forged them in their own basement or not is hard to say.

1970 Jahns Catalog:


1972 Jahns Catalog:
1968 AMX 390 w/T5
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Post Options Post Options   Thanks (0) Thanks(0)   Quote goops Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2016 at 6:45pm
I definitely had forged Jahns pistons in a 301 chevy small block in early 70,s .
they were forged for sure as I ruined 1 and had to get a replacement.
   Goops
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2016 at 7:47pm
I wish I had them catalogs to look thru.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rlumber Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2019 at 7:59am
Hello, We have a set of new 942B Jahns Pistons. Can you tell me what these were for? Thank you,
Ross
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