Stroker Rod Questions...

[AntParker]

Hi guys,

My apologies if this is not the correct area to post this.

I am putting together a pile of parts required for my 2.9 stroker build (Some of you may be aware of my other thread)

I will be using 135mm rods, My question is this: the US spec S50 engine is based on the M50 (Hence the decreased performance)
Whereas the EU spec S50 is a different animal altogether.

Does the US Spec S50 engine use the same Con-Rods as the M50, if not, does anyone know the difference plkease, and would there be any advantage to me searching for a set of US spec S50 Rods rather than EU spec M50 rods?

All a bit confusing i know, but the EU spec S50 has a larger BE and So cannot be used with the M50 Crank.


Hope this makes sense. Interested to hear your thoughts!

Many thanks

[SkiFree]

They are, for all intents and purposes, dimensionally identical. There are a couple different rod bolt lengths, but the big end, rod end, general shape, and length are the same.

[digger]

some M50 rods are 140mm (vanos) and others are 135mm(early non vanos), you want 135mm 24V rods which would include those from M52 and probably m54b30.

[AntParker]

Thanks guys, thats Great. I knew i was after the early non vanos rods but forgot to mention that part.Many thanks.

So do we think the M52 with Vanos is still using the 135mm rod then? *off to do some research*

Many Thanks

[AntParker]

Thanks guys, thats Great. I knew i was after the early non vanos rods but forgot to mention that part.Many thanks.

So do we think the M52 with Vanos is still using the 135mm rod then? *off to do some research*

Many Thanks

[digger]

quickest way to find out what engine has what dimensions is first up use an aftermarket supplier such as

http://pauter.com/parts/rods/bmw/

to narrow the search a bit

[SkiFree]

So do we think the M52 with Vanos is still using the 135mm rod then? *off to do some research*

One of the 135mm rod sets I refreshed came from an M52 Vanos, however that is only a single data point.

[AntParker]

Sorry, thanks for the replies guys... currently still on the look out for a set of the right rods... turns out S50 rods are much easier to get in Europe than M50 !

Many thanks

[Jaker]

The only US spec M50/M52/S50/S52/M54B30 rod that is not dimensionally identical for your purposes is the 140mm M50B25 Vanos (93-95 325i and 325is). All the others listed above are 135mm.

[mr2peak]

Some, however, are lighter than others. Given a choice, always go with the lightest rod that will withstand the power you want.

[Northern]

Does the US Spec S50 engine use the same Con-Rods as the M50, if not, does anyone know the difference plkease, and would there be any advantage to me searching for a set of US spec S50 Rods rather than EU spec M50 rods?

M50NV rods are 135mm, but are chunky and heavy like M20 rods - Lots of excess weight, some of which makes them a little stronger.

M50tu rods are 140mm, lighter design, but not useful for your purposes.

S50us/S52/M52 are 135mm rods, slight differences between them but significantly lighter than M50NV rods.

M54 also have 135mm rods (now fracture split) and get even lighter. Supposedly not as strong, but shouldn't be a problem for an N/A stroker build.

[ForcedFirebird]

Stay away from fractured rods on a performance build IMO. They can't be reconditioned (well, *can* be, but not practical by any means), and since they are powder forged, they will snap like a twig if tweaked. M20 rods are heavy, but they can surely take a beating and aren't very expensive. They will bend like a pretzel long before they snap... I took these out of a hydro locked motor...

[jeffnhiscars]

Can't argue with that

[digger]

I wouldnt use oe m20 rods unless you had to. There is a reason they don't make them like that anymore. Having said that the rod just connects the piston to the crank so find a set the right length with good bores and move on with life a little bit of weight is not worth worrying about on a build like this, it's the same with piston weight it's not that high on the list of important things.