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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 11-09-2012, 06:34 PM   #1
copracr
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Need some engine rebuild advice

I have an E46 2.5l that will get rebuilt with 3.0 bottom end. Is there some particular reason not to use used pistons? I usually replace as needed or on bore changes but not just because.

Any experience re-using these pistons? any problems? Thanks.
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Old 11-10-2012, 09:32 AM   #2
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Unless you have the cylinders bored out, or there was physical damage to them, I would see no reason not to re use them. I've rebuilt several engines in the past and unless the block got bored, I used the same pistons with no problems. I didn't do German cars though, only American and Japanese.
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Old 11-10-2012, 02:34 PM   #3
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Just buy a used 3.0 litre, easier and arguably more reliable. Short block if your cyl. Head is being rebuilt. Long block otherwise
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Old 11-10-2012, 02:56 PM   #4
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He should be able to reuse his OWN pistons. The OP is asking me to sell him a crank/rod/pistons. I am refusing to sell him the pistons. That is why this thread is here. With all this being said, I'll wait on a buyer that knows wtf he is doing. So it doesn't come back on me. /end thread

Last edited by xixixi; 11-10-2012 at 02:59 PM.
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Old 11-10-2012, 03:04 PM   #5
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Wow, I had asked you if you knew why used pistons were a bad idea. You didn't have an answer, and being a curious individual I thought I'd get some perspectives on the practice.

You're right though, you will wait on a buyer.
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Old 11-10-2012, 03:14 PM   #6
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Wow, I had asked you if you knew why used pistons were a bad idea. You didn't have an answer, and being a curious individual I thought I'd get some perspectives on the practice.

You're right though, you will wait on a buyer.
Unwilling to give you an answer, is not the same as not knowing.
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Old 11-10-2012, 03:50 PM   #7
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You didn't have an answer for me, whatever. In my experience pistons rarely wear out. Sometimes they they wear out the landings, but most often something happens to them to destroy them e.g. ran lean, overboosted, over-speed melting, etc.

I thought maybe BMW pistons had some high tech property which made them wear out- like those nikasil cylinder walls or something.
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Old 11-10-2012, 03:56 PM   #8
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You didn't have an answer for me, whatever. In my experience pistons rarely wear out. Sometimes they they wear out the landings, but most often something happens to them to destroy them e.g. ran lean, overboosted, over-speed melting, etc.

I thought maybe BMW pistons had some high tech property which made them wear out- like those nikasil cylinder walls or something.
Hit my previous post on the head, well done. Do you honestly think, I'd sell you a used piston and encourage you to put it in your engine? REALLY??? If a crank is scored, a rod is bent. I can detect that, how a used piston will work in your motor. I have no idea, you are making me out to be a dick. When in fact, I'm trying to save you from yourself, without giving you an explanation of why.
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Old 11-10-2012, 04:51 PM   #9
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I just asked if pistons were included, you said no, I asked why? I wasn't trying to hound you, and I've just never heard of a good looking piston not being routinely re-used.

Must be a BMW thing.
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Old 11-10-2012, 05:02 PM   #10
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I just asked if pistons were included, you said no, I asked why? I wasn't trying to hound you, and I've just never heard of a good looking piston not being routinely re-used.

Must be a BMW thing.
I don't disagree with you, I don't feel comfortable selling you used pistons. Maybe I misunderstood what you were asking, I apologize for that. If you want 6 pistons that are the same as your own. I will give them to you.

Last edited by xixixi; 11-10-2012 at 05:03 PM.
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Old 11-11-2012, 08:13 AM   #11
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Quote:
Originally Posted by copracr View Post
I just asked if pistons were included, you said no, I asked why? I wasn't trying to hound you, and I've just never heard of a good looking piston not being routinely re-used.

Must be a BMW thing.
I don't understand why you seem insistent about getting his pistons (...sounds funny...you want his pistons)?

He doesn't want to sell them...end of story.
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Old 11-11-2012, 10:42 AM   #12
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I don't understand why you seem insistent about getting his pistons (...sounds funny...you want his pistons)?

He doesn't want to sell them...end of story.
I don't want his pistons, that's what I'm saying. I asked if they were included, he said he wasn't selling them, I asked why? He wouldn't give me a reason.

I posted this thread for the sole purpose of finding out if used pistons were not re-used on e46's, and if so, then why.

That's it, I wanted to know for my own experience. THen he got it in his head I was bugging him. Here's the PM's:

Quote:
Originally Posted by xixixi
Quote:
Originally Posted by copracr
Quote:
Originally Posted by xixixi
Quote:
Originally Posted by copracr
Quote:
Originally Posted by xixixi
Quote:
Originally Posted by copracr
Hi, I did read a little about swapping the 325 guts over to 330. If I got this right, I'd been the crank, rods, and pistons? And how much would you want for them?
450
Sounds reasonable, what condition are they in? Could you mail some pics to copracr@gmail.com?
I wouldn't reuse the pistons, I gave you the price for the crank/rods. I will get ya some pictures, tomorrow.
THanks. Why not re-use the pistons?
I've just never really sold any, I suppose you could reuse them. If you bought new rings.
THen I posted this thread to get some more info.
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Old 11-11-2012, 11:11 AM   #13
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I don't want his pistons, that's what I'm saying.
Sorry...I'll grow up. now.
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Old 11-21-2012, 03:28 PM   #14
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People often re-use pistons and rods. Especially in a straight 6, the primary and secondary balance of the engine is perfect and usually requires just a set of bearings and a light hone with new rings...ect
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Old 11-21-2012, 03:38 PM   #15
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Sorry...I'll grow up. now.
funny funny
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Old 11-21-2012, 06:42 PM   #16
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People often re-use pistons and rods. Especially in a straight 6, the primary and secondary balance of the engine is perfect and usually requires just a set of bearings and a light hone with new rings...ect
This isn't a practice I feel comfortable supporting. I'm not saying it doesn't work. I just don't want to involve myself with it. The parts I get are used. I have as much information about them, as the tech that pulled them. It's much cheaper to buy a used motor than to rebuild an old motor. I can give you first hand exp on this, I broke down 3 blocks. All of them seemed decent, and rebuildable. Not 1 of the 3 were good. Everyone I've sold bottom ends to are from another forum. They source their own pistons, S50's, M52's, etc

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Old 11-22-2012, 11:20 AM   #17
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This isn't a practice I feel comfortable supporting. I'm not saying it doesn't work. I just don't want to involve myself with it. The parts I get are used. I have as much information about them, as the tech that pulled them. It's much cheaper to buy a used motor than to rebuild an old motor. I can give you first hand exp on this, I broke down 3 blocks. All of them seemed decent, and rebuildable. Not 1 of the 3 were good. Everyone I've sold bottom ends to are from another forum. They source their own pistons, S50's, M52's, etc
Whats the problem with using rods and pistons that are still in spec?

The information you have is when you mic the bottom and top end for specification.

Cheap isnt always the best option. Blueprinting an engine(even on a napkin) that your going to throw into your car is much better than just tossing in an unknown used engine.

Many times ive seen an engine with 200,000 miles that burned a little oil from tired rings. The cylinder walls had hardly any taper, the rods and pistons were still within' a gram (the weight of a dollar bill) between eachother. The rods and rod ends had no out of roundness and with the correct length. crankshaft needed nothing but a polish and a standard set of bearings.

Back in the old v8 days, yeah...after 100,000 you would have issues...usually.

Modern engines are built with tighter tolerances and balanced better than ever with computer aided machine equipment, so the service limits are much more forgiving.
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Old 11-22-2012, 12:48 PM   #18
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From a liability standpoint I could see not using them, and that would be about it...other than obvious damage.
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Old 11-22-2012, 04:16 PM   #19
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Every cylinder wears differently a modern engine with 200k or even 100k nothing is round. It has worn and is oval, I don't wanna be the guy on the hook. I could sell pistons, I have about 20 in my trash atm. Ethics, not gonna do it. If you have the thing apart, put better pistons in it. It doesn't make sense to take a chance. I like to do everything ONCE the RIGHT WAY.

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Old 11-22-2012, 07:59 PM   #20
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Every cylinder wears differently a modern engine with 200k or even 100k nothing is round. It has worn and is oval.


I swear Im done with you.
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