Inline 6 cranks

[SilentRavens]

Hi everyone...

Exactly how similar are the 2.5l engines through the various models. Could I fit a much more modern 2.5l crank into a M20 as part of a stroker? Does anyone have the specifications available for the M50 and up cranks?

Thanks

[Digitalwave]

2.9L+ strokers use custom S50 cranks.

[SilentRavens]

As in a reground S50 crank? As far as I can tell the common place stroke length is ~75. To make a mild stroker (2.7-2.8) it looks like I will need an "e" or td crank, no?

[MR 325]

Yes if you want to build a 2.7 or 2.8 you should use the Eta or 524td crank. I am running an Eta crank in my 2.7 stroker. If you haven't found this site yet, it might help you out a lot. www.strictlyeta.net

[SilentRavens]

Yes, looking at that site is what started me in the stroker direction. 8)

Okay one more question for you guys, for those running with cast "e" cranks what has your experience been with how much the engine can be revved. Right now I have a stock 325I and I like being able to let the the engine run up to 6-7k rpms, only when I need to of course ;) .

[MR 325]

I just got my car running yesterday, so far have brought it up to about 4000 but I haven't driven it yet. I will let you know how well ti revs once I drive it.

[Jon325i]

I have heard of 2.7/2.8L M20s w/ Eta cranks being able to rev to 6500+rpm w/o issues. Anything higher is pointless on a street engine.

Jon

[Jordan]

My 2.8L 10.2:1 stroker with a cast eta crank has no issues revving to 7100rpm. Perfectly happy.

Unless you are going FI, or the engine will see serious sustained high RPM track abuse... there is no need for a forged crank.

[SilentRavens]

Thanks you all for your replies...

[SA E30]

M52B28

84mm throw.

Thats about the longest u can go before u have to start working on the crank, and the block for clearance... makes for a very inreliable engine (cause the crank is really hard to re-balance perfectly)

Know a guy here, who ran an S50B30 crank on M3 pistons, not sure what rods, but the motor laster all of 10 000km... then the crank shook itself to death... this was built by one of South Africa's top BMW tuners.