Hi. mart has been kind enough to locate some 331 pistons for me. Here is a picture of one. Looks like a Jahn's piston to me. Any idea on compression ratio? I think it's certainly safe to say it's higher than the 7.5 I currently have. Thanks yall. And thank you mart!
Piston ID Help.
Moderators: scottm, TrWaters, 392heminut
Re: Piston ID Help.
Jahns often put their name on the inside, so if it is bare then look for a number of some kind. It is obviously higher than 8.5 since they were flat-tops. If they will fit in your bore as you had wanted then hook up a rod and crank and check the down fill volume to determine dome volume. Easier to make a guess at that point.
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Early Hemi Parts and Pieces,
INVENTORY CLEARANCE IN PROGRESS. See website for details.
Early Hemi Parts and Pieces,
INVENTORY CLEARANCE IN PROGRESS. See website for details.
Re: Piston ID Help.
I take it you didn't get them in the original box.
Re: Piston ID Help.
No. I actually don't have them yet. I am working out a deal with the owner. I will probably go ahead and get them because surely they are over 7.5:1. lol As long as they aren't 12:1 or higher, I think I'll be ok.
Re: Piston ID Help.
If he has the box the CR is @ the bottom of the label, possibly curled under on the bottom of the box.
Re: Piston ID Help.
----------------------George wrote:If he has the box the CR is @ the bottom of the label, possibly curled under on the bottom of the box.
I doubt he has the box because, I'm pretty sure these pistons are used.
mart
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Re: Piston ID Help.
I got me some pistons. Old on the left. New on the right.
Re: Piston ID Help.
------------------Rob wrote:I got me some pistons. Old on the left. New on the right.
NICE!!!! It looks like the domes are about a 3/16 of an inch or so taller than the original truck 'flattops'. Not much... but enough to make a noticeable difference in power output for sure. The small dome should be good for about 1.5 to 2 points over the stock 7.5 to 1 truck pistons. And being 354 pistons too, the 23 extra cubic inches over the 331, also won't hurt anything in the power department either!:D
mart
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Last edited by mart on Sun Jul 03, 2011 12:21 am, edited 1 time in total.
Re: Piston ID Help.
So wich pistons are you going to use?