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Discussion Starter #1
Could you guys please help me identify what type of pistons I have here and tell my why one is different from the rest? The other side of the engine matches this side too. Makes me think something is out of balance. Why have two different pistons out of the 8? The engine was rebuilt by previous owner and never totaly reassembled. I'm trying to see what I have here.

Thanks for any help.
Scott
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It's hard to tell from the pictures, but it looks like you have two different styles of dished pistons. This is not a problem for a stock street type engine if the dish volume and piston weight is the same. If the engine does not vibrate and runs OK for your purpose, I wouldn't worry about it. It does make me wonder about the engine builder. Cast pistons are cheap enough that I would have put in a whole new set instead of mixing them up.
 

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Weird. I guess if there's one in the other bank on the same crank throw it would balance out. I'd hate to find out otherwise once you got everything buttoned up. How much would new pistons set you back?
 

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IMHO the engine doesn't know the difference. I would guess that since the pistons don't match and the engine has been bored, the guy just took what the parts store had in stock. I wouldn't worry about it, as Ford Crazy said, in a mild street engine. If the engine has been only re-ringed however I would guess that there were a couple of pistons with broken skirts and only they were replaced.
 

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Aside from balance, you will also have a different chamber volume and CR for those two pistons. How much would have to be determined.

If the engine has run like that with no issues, great, but I would personally replace all of them just for the peace of mind of not having to worry about it later.
 

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Discussion Starter #6
This is a fresh rebuild....never ben run. I'm leaning toward replacing them all.
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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I once got in a rush and figured cheapo parts store pistons would do. They got them the next day. Eight pistons. Two were apparently made by Badger and six by TRW. Three were standard bore, one .020 oversized, and the rest .030's I had ordered. I confounded that they could screw it up that bad. I threw that entire mess back and just held on until Summit got me a set of hypereuteutics which were what I really wanted to use anyway.
I doubt there'a any real harm in the mismatched pistons. But me, I couldn't stand it, I'd have to have matched set.
 

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If $$ are not terrible, I'd replace them with all the same thing. You'd be assured of even compression. Man, getting it all together and then discovering that there are two ratios would pretty well ruin my day....
 

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It's possible the mismatched piston is in a cylinder that was bored to a different oversize. I'd definitely check that.

Frank
 

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Discussion Starter #10
Good point...I will.
 
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