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Jahns pistons

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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 7:45pm
That is ok, just look at them closely to make sure that they don't have material removed for clearance. If they do then when you do assembly you probably will want to run the piston up to TDC and check for clearance issue with the head itself to ensure no interference.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SKeown Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 12:19pm

 To the best of my knowledge Jahns never made forged pistons, only cast. If they are forged then they were made to Jahns spec by Ross.

 SKeown


Edited by SKeown - Sep/14/2016 at 12:26pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 1:06pm
Originally posted by SKeown SKeown wrote:





 To the best of my knowledge Jahns never made forged pistons, only cast. If they are forged then they were made to Jahns spec by Ross.

 SKeown



Unless my memory is failing me, I was buying Jahns forged pistons for Mopars in the early '70's prior to Ross even being in business.
Roger Gazur
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 2:14pm
Jahns are a bit before my time of performance builds. Dad was installing them when I was still handing him wrenches and asking a bunch of questions but no direct experience myself. Either way if they are Ross or Ross bought them they would still be nice pistons.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 2:25pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 2:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Woosterkevin Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 2:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Sep/14/2016 at 3:48pm
They are definitely cast but they also appear to be very nice cast piston.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/15/2016 at 8:32pm
I would say those look forged, not cast. Cast pistons have a shiny look to the metal surface when you look at the underside, and forged pistons have a more satin finish like these do. Also forged pistons have a more gradual radius to corners on the underside than cast (other than the areas that have been machined of course).

Here's a cast Subaru piston: 



And a forged one:



Edited by Greyhounds_AMX - Sep/15/2016 at 8:40pm
1968 AMX 390 w/T5
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TX390AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/16/2016 at 6:32am
I'd also watch your cam lift spec's. Even with the valve reliefs, you wouldn't want to risk those nice pistons with a big lift cam.
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