M50 main bore spec?

[derrty 30]

does anybody know what the spec is suppose to be for the main bore on a nv m50b25? only thing i can find is on prosis, and it says 2.5590-2.5598"(64.999-65.019 MM) but all of my mains are about .0015-.0010" too small. engine ran great before i pulled it, main bearings looked perfect, crank is perfect, just wanted to know if the spec i found was right. and if it is, why are my mains smaller than spec?

[jon2681]

this is what i found for vanos tho. i guess there the same here is non vanos http://tis.spaghetticoder.org/s/view.pl?3/01/61
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BMW TIS - 11 21 Crankshaft and Bearings M50 B 25 VANOS Ground sizes of main bearing journals

11 21 Crankshaft and Bearings M50 B 25 VANOS

Ground sizes of main bearing journals

Standard yellow mm59.984 ... 59.990 Standard green mm59.977 ... 59.983 Standard white mm59.971 ... 59.976 Undersize 1 (U 0.25) yellow mm 59.734 ... 59.740 Undersize 1 (U 0.25) greenmm 59.727 ... 59.733 Undersize 1 (U 0.25) white mm59.721 ... 59.726 Undersize 2 (U 0.50) yellow mm59.484 ... 59.490 Undersize 2 (U 0.50) green mm59.477 ... 59.483 Undersize 2 (U 0.50) whitemm59.471 ... 59.476Radial crankshaft bearing playmm0.020 ... 0.058
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[derrty 30]

i need the main bore size...not the bearing size

[derrty 30]

anyone?

[!kid]

Your best bet would be to call VAC Motorsports. I've asked questions like yours on this forum before with not much help. Also what are you using to measure the main bore? You really need a dial bore gauge that can do .0001" increments.

[derrty 30]

Your best bet would be to call VAC Motorsports. I've asked questions like yours on this forum before with not much help. Also what are you using to measure the main bore? You really need a dial bore gauge that can do .0001" increments.

yes it reads .0001" increments, im using a very nice dial bore gauge. no cheap tools where im at

[!kid]

I just got off the phone with Steve from VAC Motorsports, got some info for my cylinder head build. I asked him about the main bore size, unfortunately he did not know the size and his engine builder is out for the week(sick) give them a call some time next week I am sure they will be more than happy to help, they have been helping me out a lot!

He also stated that it can be hard to find engine specs because BMW does not release that info.

[derrty 30]

I just got off the phone with Steve from VAC Motorsports, got some info for my cylinder head build. I asked him about the main bore size, unfortunately he did not know the size and his engine builder is out for the week(sick) give them a call some time next week I am sure they will be more than happy to help, they have been helping me out a lot!

He also stated that it can be hard to find engine specs because BMW does not release that info.

thanks, and thats pretty dumb that they dont release that info...

[!kid]

The reasoning is BMW wants you to buy a new engine and not service them. Yeah I think it's dumn too.