ID my stroker please

[riceh8r]

so i found that an m52 crank had been installed at some point. part number comes up with no matches that i can find tho...1280969. pistons are mahle 83.98 (was hopeing to find them +1mm, but nooooo). rods are just hardened chrome, have not measured length yet, part number 1717085, again no matches anywhere that i could find. just curious...i am ordering parts for assembly, and this caught me by surprise. basically i am guessing i have a 2.8L now instead of a 2.5L ? someone set me straight, 'cause i am having no luck with my searches. why would a bmw part that has cast part numbers on it, not show up on a search. thanks.

[323iNathan]

well an 84mm bore and 84mm stroke (m52) gives 2.8L, so i'd say you guessed right.

Edit: Sorry for the triple post (I've deleted them now) internet troubles ftl!

[riceh8r]

thanks for the verification. got my head and block back from machine shop today. honed cylinders look sooo good. machinest was impressed...he doesn't see many bmw parts. shaved head, new guides and seats reground make me feel all warm inside. masked off and painted block, just finished.

[ForcedFirebird]

Just came across this post during a search. Have an m20 block here at my shop and need a 75mm crank for a rebuild of another engine. Crank still in the block (also timing cover is still on, so can't see oil seal spacer) with casting number 1280969. Thought for a minute I had a b28 crank that I came across somehow. Grabbed a mechanic's straight edge to put across the block and measured the throw, it is in fact a 75mm b25 crank. Thought I would post up in case anyone else comes across this. If the crank doesn't have a spacer on the front with this part number, it's just a stock m20b25 crank.

[ForcedFirebird]

Furthermore, went through the cranks at the shop and there's an easy way to identify them at a glance. "H75" is cast on all the 75mm cranks, "H81" is cast on the 81mm cranks, and so on. 24v cranks I have here use "Hub" as a prefix.

[10Toes]

B28 crank is also forged and looks quite different then the non-forged cranks, also B28 have a blue tint to them. They will also have the crank position wheel on the crank.

[ForcedFirebird]

Putting this part number in Google and there are tons of posts claiming it's a casting number for a b28, and people pass the information around as if they knew it as fact. Spent some time translating German pages to find the "H75" etc designation information, and backed it up in real life and thought it would be good share for future searchers, specially since this is one of the first that comes up on Google. The "H" designation is also good info for someone purchasing a crank, that may not be what they think they are getting when purchasing over the internet as from afar one OBD2 crank could be hard to tell from another in pics.

Didn't even think about the trigger wheel for the OBD 2 cars when replying :(

[ForcedFirebird]

B28 crank is also forged and looks quite different then the non-forged cranks.

Also have read this, but when digging through pics of crank comparisons, who knows if this is true, either. Are ALL b28 cranks forged? According to this post below, the b30 (b32) crank appears to be blue, the b28 crank appears to be cast just like the m20 crank is. We are putting an m52b28 in an e30 next week or so, the pan will be coming off - will be interesting to also confirm that first hand (have the VINs on it still).

Can't tell you how many times on forums, someone posts misinformation, and it gets repeated over and over as fact when the re-posters have no first hand experience with it, yet state it as fact. Then it seems this info gets spread as gospel.

Here's a photo of 3 cranks. Top to bottom they're M54B30, M52B28 and M20B25.



Their "outer diameters" are approximately 140, 134 and 132mm respectively. Thus the M54B30 crank gives an extra 14.4mm stroke while it's only 8mm larger externally. Will post a photo later of it in an ix block.

And in case it's of any future use, the M54B30 crank has a casting number of 1403866 and the M52B28 crank has a casting number of 2242898.

[Bullet Ride]

Here's my B28 vs B25 picture. My B28 crank had a blueish tinge to it. In the picture above the B28 counterweights look much thicker than the ones on my crank. I wonder if there was more than one supplier for the cranks?

[LJ851]

I thought all bmw cranks were forged except the eta cranks.

A forged crank (or anything for that matter) is easy to ID. A forged crank has a wide parting line, like 6mm or more whereas a cast crank has a very thin parting line.

[ForcedFirebird]

I wonder if there was more than one supplier for the cranks?

Or certain chassis got forged? Also forged cranks that I have dealt with in the past from other platforms have not had any color difference. When working in the CNC machine shop, color of the final product usually depended on the post process treating.

When younger, we would tell a forged crank by tapping the front hub/damper bolt with a hammer. A cast crank wouldn't make much noise, whereas a forged crank would ring for a bit - harder to say these days since metal composition has come a long way. Steel can also be cast (vs nodular iron), and then there are several casting and forging processes in modern days that make a parting line difficult to be a deciding factor. Even forging processes have changed a lot and has variations - perhaps only BMW will know.

Either way, looks like there is possibly two types of b28 cranks. Will report back when this engine gets opened up, for sure.

[Bullet Ride]

On realoem there's 3 part numbers for the cranks

11211744979 and then there's 11211709059 which was replaced by 11211433026.

[4x4_e30]

When younger, we would tell a forged crank by tapping the front hub/damper bolt with a hammer. A cast crank wouldn't make much noise, whereas a forged crank would ring for a bit - harder to say these days since metal composition has come a long way. Steel can also be cast (vs nodular iron), and then there are several casting and forging processes in modern days that make a parting line difficult to be a deciding factor. Even forging processes have changed a lot and has variations - perhaps only BMW will know.

According to every source I've found, the parting line is the most obvious indicator of forged vs cast crankshafts. Then comes the hammer trick. I got a m52b28 crank at the junkyard from a 98 328i for $30. It has a wide parting line, and rings like a bell when hit with a hammer. My stock m20b25 crank has a thin parting line, and barely rings for a second or two.