I need somebody to sell me pistons or a full M30!!!

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keehn
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I need somebody to sell me pistons or a full M30!!!

Post by keehn »

Help!

My M30B30 block bore is too large for the stock piston ring clearance, so I am looking for alternatives. Dealers online have listed the oversized pistons as unobtanium, and junkyards in my area don't have any 70-80's M30 bimmers in stock.

Does anybody have a full M30 or oversized pistons they would like to sell to me? I was desperate to keep the block, but if I cannot find oversized pistons, then I need to bite the bullet and find alternative solutions.

Thank you!

Mike
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

Eff it,

I sent back the normal sized rings because the gap was too large and ordered the .50 set. Upon realizing that the entire piston needed to be replaced to use the bigger ring (it's thicker), I'm going to re-order the normal sized rings and just tolerate the excessive gap, and send back these oversized rings :cry: .

I have already sprayed some dry-film lubricant on each piston skirt; I may spray a few more coats on top one another; maybe that will help reduce piston slap? In any case, I've already invested WAYYYY too much time and money into this block to quit now. Piston ring gap or not, Eleanor WILL drive again!

BUT, I AM still in the market for 0.25 oversize pistons or a complete M30 block. Maybe I'll use it in Eleanor, or I'll simply clean, prep, and rebuild for another BMW I'm sure to be in the market for later on.

Mike
PatinaBeforePolish
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Re: I need somebody to sell me pistons or a full M30!!!

Post by PatinaBeforePolish »

Keehn,

I have a set of NIB 86.08 with rings if that's any help. I think you want 86.22 though. I also have a 1980 block with about 89k on it that you're welcome to have at no charge. About 1 1/5 to 2 hours from you.
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

PatinaBeforePolish wrote: Thu Apr 16, 2020 9:48 am Keehn,

I have a set of NIB 86.08 with rings if that's any help. I think you want 86.22 though. I also have a 1980 block with about 89k on it that you're welcome to have at no charge. About 1 1/5 to 2 hours from you.
Patina,

I PM'd you.

Mike
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Lock
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Re: I need somebody to sell me pistons or a full M30!!!

Post by Lock »

Just a thought.. the M30b30 block is 89mm bore, and the m30b34/b35 block is 92mm. You could bore it out and get a set of those commonly available pistons. And end up with a 3.2l block. Throw an 86mm crank in there and you'd have a 3.4l. But that leads down a dark path, at that point it'd probably be best to start with a b34 block with the original cylinder wall thickness.
Getting those pistons from Patina is the more responsible option.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

Lock,

Your post caused the light in my head to turn on (or, perhaps, the hamster to turn the wheel); why not overbore and put in oversized pistons? The block is stamped "3.0/3.3" and the cylinder wall is pretty thick, so overbore (to 92mm) wouldn't cause water jacket failure.

I just jumped on a set of $200 pistons on eBay (BMW part 11251286435) that should work perfectly fine with the rest of my rotating assembly (conrods are identical).

Now, I need to find a REPUTABLE machine shop in my area. I used one shop when I did my Buick Enclave and I wasn't particularly happy with their work, but that's my problem to solve.

Thank you for the lightbulb idea!

Mike
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528i-1981
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Re: I need somebody to sell me pistons or a full M30!!!

Post by 528i-1981 »

And thus the 532i was begotten.
(oo=00=oo) Eric
1981 528i Manual
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

:lol:

I've been reviewing the interchanges between the 3.5l and 3.0l parts and if I wanted to make a true "stroker", I would need to get a different camshaft, sprockets and chain.

Instead, I'm going to settle with merely boring out to 92mm to fit the updated pistons and use my existing rotating assembly. I don't think it will give me much of a HP/torque boost, but it's still more displacement than the old 89mm bore.

Mike
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

So, I may have a lead on an 86mm crank and 3.5l cylinder head.

.....the 532i Eleanor might be a possibility after all.....

MTF.

Mike
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Lock
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Re: I need somebody to sell me pistons or a full M30!!!

Post by Lock »

You've chosen the dark path! But it's so easy to go a little bit further, and just a little bit further again.. Especially given so many parts are interchangeable. That the conrods are the same from the 2.5 to 3.5 for example makes things so easy.

The only thing to keep an eye on is the B35 has a larger combustion chamber capacity, and the (US) B34 pistons are dished so just don't match B34 pistons with a B35 head. Unless you want ~7:1 compression for a crazy turbo application, which has been done.

For me, I'm doing the reverse - to keep the log manifold, I'm using the B34 head, but using B35 pistons for an apparently 9.5:1 compression ratio. It might not have a huge top end, but should have a very good low and midrange.

Like I say, each step is only a little bit more, and if you've gone that far...
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

Today, I picked up the 86mm crank and corresponding 3.5l head (with camshaft sprocket...VERY important to have!).

So yes, I have chosen the dark side. I looked up engines and it appears that BMW never made a 3.2l for the E12, making my build unique in that regard. While I do have the 3.5 head, I'm going to keep with my planned AMC head, mainly because everything has been purchased and I don't feel like packing up and returning certain parts like I've had to do with piston rings.

I'm expecting the pistons to arrive sometime this week, at which time I'm going to send my block off to a local machine shop (that has good reviews) for 92mm boring. I'm going to buy the corresponding chain (don't want the valves slapping the piston heads!) and have that on standby.

Once all that's complete, reassembly can officially begin and the Eleanor project can get back on track. Eleanor will become a 1976 532i!

Mike
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keehn
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Re: I need somebody to sell me pistons or a full M30!!!

Post by keehn »

Also wanted to mention that the crankshaft and head come from Al Taylor. His backyard at ONE of his properties (the one I visited) is littered with vintage bimmers in various states of disrepair. He has DOZENS of vintage BMW's. If I didn't have a 4-hour drive back home, I would have spent all-day just rooting through his collection.

I think this man has virtually every vintage BMW part known to exist! We spent a good hour or so talking about him racing his E9, driving a Bavaria through a snowy overpass (he's not called "Crazy Al" for nothing), and his business in general. He is very down to earth and seems like a great guy. If you google "Al Taylor BMW", his name is littered through several online forums, so although this is the first I have heard of him, he has established a well-known reputation with many vintage BMW enthusiasts.

Man! If I lived closer to him, I'd probably end of being the Kramer to his Seinfeld! :lol:

Mike
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