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      10-27-2019, 08:16 AM   #1
lrz
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Z4M: New engine or stroker kit, which route to choose?

Hi,
My s54 Z4M engine is suffering from damaged crank and connecting rods due to bad rod bearings.

I'm debating which route to choose to fix the problem, whether to replace the whole engine or install a stroker kit (VAC) on the existing one.

My questions are:

1. What is the most recommended route for this situation?

2. In terms of working hours, what is more complex and requires more work time?

3. Will the stroker kit be enough to solve the problem or will I need to replace additional parts of the engine?

4. If I choose the stroker kit and I want to install FI (SC) in the future, what are the recommended dimensions/settings?

Any information is important and can help a lot.
Thanks!
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      10-27-2019, 12:32 PM   #2
Mirko
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Hi, there are a few threads similar to what you are asking, they are scattered i think in general and in the engine sections. A couple of people have built stroker kits and I think going with 3.4 instead of 3.5 was the better option.

If it were me and forced induction was my final position then I would buy another s54 and just add the forced induction to it. I dont think it makes sense to increase the engine size (3.4l instead or 3.2l) and then add forced induction. Seems like spending more money than needed on the internals which could be offset with a bigger blower or cooling which I think is cheaper than opening up the engine. I think it would be cheaper to just build the engine in one direction from the start. I also think FI is cheaper overall per hp than opening up the engine and increasing its size.

Personally I'd rather just increase to 3.4L and not do forced induction as it would keep the character of the s54 but just increase the power. Forced induction can introduce lag and shift the power band.

I think your best bet is to talk directly to VAC about cost and options since they build engines they would know best. Sorry I can't be of much help but curious of outcome. please update us!
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      10-27-2019, 02:18 PM   #3
Michael9218
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The sensible thing to do is find a replacement motor, preventatively replace the rod bearings and rebuild the vanos and it's plug and play.

The stroker kit isn't a simple replace the rods and crank situation. You're looking at a complete rebuild and machining work, not to mention other cost over runs. Very poor bang for buck.

As for FI, personal choice. But a solid stock motor is where you want to start.
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