M30B34 M30B35 crankshaft: differences?

E28 technical advice asked and given! Troubleshooting, modifications and more.
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pavulon
Posts: 48
Joined: Mar 10, 2018 8:39 PM
Location: WI

M30B34 M30B35 crankshaft: differences?

Post by pavulon »

Are they the same BMW piece? If not, how do they differ?

Thanks in advance.
Mike W.
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Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: M30B34 M30B35 crankshaft: differences?

Post by Mike W. »

According to the bible, Realoem, they're the same. Now that might just mean they're interchangable and only the current part number is listed, BMW has been known to do things like that.

Now I know I've heard the block is stronger on B34s, and Realoem again shows it slightly heavier by 3Kg, but I can't say for sure on the original cranks.
Nothintoseeere
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Joined: Apr 23, 2021 5:27 PM
Location: U.k

Re: M30B34 M30B35 crankshaft: differences?

Post by Nothintoseeere »

There are no practical differences between the blocks ,cranks and conrods, they can be used in any m30 engine. The Pistons differ meaning the heads are not interchangeable without changing the pistons.
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: M30B34 M30B35 crankshaft: differences?

Post by Mike W. »

Nothintoseeere wrote: Oct 10, 2021 1:15 PM There are no practical differences between the blocks ,cranks and conrods, they can be used in any m30 engine. The Pistons differ meaning the heads are not interchangeable without changing the pistons.
No, aside from the blocks being slightly heavier, which may translate to stiffer, or may not, the motor mount bosses aren't in the same place. Using an earlier block in my E28 I had to fab up a new motor mount, and it's well documented that only the earliest B35 blocks will bolt up to an E28 with out the special adapters from I believe it is Koala Motorsport. Now in mechanical rotating parts, yes, but there's more than that.
pavulon
Posts: 48
Joined: Mar 10, 2018 8:39 PM
Location: WI

Re: M30B34 M30B35 crankshaft: differences?

Post by pavulon »

Thanks all!
Nothintoseeere
Posts: 57
Joined: Apr 23, 2021 5:27 PM
Location: U.k

Re: M30B34 M30B35 crankshaft: differences?

Post by Nothintoseeere »

Oh that's is not something I was aware of so just the cranks and conrods are interchangeable then.
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