what is the difference in the cranks?

[der affe]

so what is the difference between an s-50 and an m-50 crank? pardon my non-m-20 ignorance

[SpecM]

-s50 has longer stroke, so the crank throw is longer. Also the s50 crank is forged, and I'm not so sure the m50 one is (but maybe?).

[der affe]

does anyone know what the strokes of the two cranks are??? 84mm 86mm 89.6mm???
ok an s-50 is 86.4, so what about the m-50??

[Jarvis]

That information can be found after 5 seconds of searching on google. Or probably even the technical forums here.

[der affe]

ok s-50 is 86.4mm stroke what about the m-50??? and is that a forged or cast crank? staying n/a so not real concerned

[der affe]

i'll try google no luck here using the search, that's why i posted

[nando]

M50B25 is the same stroke as our M20, 75mm

M52B28 has an 84mm stroke

[der affe]

ahhhhh ok that HELPS out ALOT! now it makes sense!
thanks for the help!
greg

[Madhatter]

S50 is 85.8mm, just a tick under 86mm, along with the 86mm bore of the motor, giving you 3L :)

The S50 is basically an M50 motor, thats why you will see M50/S50 listed in some forsale cranks for M3 items.

Basically stroke runs down like this

M50 2.0 - 66mm
M50 2.5 - 75mm

M52 2.0 - 66mm
M52 2.5 - 75mm
M52 2.8 - 84mm

M54 2.2 - 72mm
M54 2.5 - 75mm
M54 3.0 - 89mm

S50US - 85.8mm
S52US - 89.6mm

All the above share the same bearing sizes because the M50/M52/M54 are basically engines built from the original M20 block design (with a few modifications), so they carry over the 60mm main and 45mm big end bearing sizes. Only one im not sure about is the S52US (we never had them here, euro engines are different as i said earlier), but im pretty sure it was still built from an M52 block so it shares the same bearing sizes as above.

So thats why they can be used in M20 engines, you just have to machine up a sleeve for the crank (because the later model engines are chain driven, they dont have a lip on the nose for the front seal), then match piston/rod sizes to make it all fit in the block (the M20's deck height is 2mm shorter than the M50).

[der affe]

THANK YOU MADHATTER!!!!!!!!!
that is the info i need for my engine and can't seem to find here or everyone tells me to do a search for (which has not revieled anything using the search). sticky this!!!!! i am sure there are PLENTY of other people who would benifit from this info!!!
thnaks again for sharing
greg