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ron37
Jahns Pistons


Picked up a set of Jahns hemi pistons. The number cast inside is 942R. Diameter checked out at about 3.79. The guy said they were .020 and 3.8 for a 56 Dodge hemi. Checking my books, sounds more like a 341 or 345 Desoto. Mainly I am interested if anyone knows the compression ratio. I have a 330 Desoto to build and that would make it .080 over.
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on: Sat 22 of Apr, 2017 [15:51 UTC] reads: 2578

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ron37
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Re: Jahns Pistons
on: Sun 23 of Apr, 2017 [21:11 UTC] score: 0.00
Well the box has a McQuay-Norris label with 8 - P425 NX .060 Aluminum Pistons. Some one wrote card 2920, which probably means nothing. Then on the top someone marked 315 hemi. On the side they wrote 3.805. Below that 11.12 to 1 CR. So I think all this is wrong. They are cast with the web inside the top of the piston . They have JAHNS cast inside on one side and 942R on the other side by the wrist pin boss. I got out the mic and did some measuring. The piston diameter is 3.79. Height from top of the dome to the wrist pin is 1.947. Wrist pin diameter is .964. So from the top of the dome to the center of the wrist pin is 2.429, if that helps. Just curious as to what I got.

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DaveBlakeman
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Re: Jahns Pistons
on: Sun 23 of Apr, 2017 [15:44 UTC] score: 0.00
My 1965 Jahns catalog shows a F942HR Then it has some specs 2 1/16 for 9:1 cr 2 1/8 for 10:1 Comp rat and 2 3/16s for 11:1 comp rat. The number 2 1/8 may be the height of the dome off the top . This catalog is for cast pistons only . These are in the Chrysler section.

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George
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Re: Jahns Pistons
on: Sun 23 of Apr, 2017 [01:16 UTC] score: 0.00
Do you have the OEM box?


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