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The question may be foolish, and also, it may have already been placed and answered, but I did not find any related thread:
How easy or difficult is to fit an S14, given it is based on M10?

Well, of course I guess the most difficult part is to find one hahahaha
however, if found, what are the problems/issues that would have to be sold? Will it match the M10 gearbox, if, say, the M3 gearbox is not sold with the engine?
How about speedo issues?

I have s14 under e21 hood. Still not working but should be in couple month.
As I had a different approach - this is race car and engine was pushed some good 5cm back from where BMW engineers could have put it I can't tell if original m10 engine mounts would fit. I guess the should. But what I know for sure is that s14 oil sump won't fit. the left side of it will end up in frame. Also flywheel cover won't fit, but it can be replaced with original m10. There will be issue with gearbox. Well not with fitting it but with original s14 sensors which are placed on gearbox bell. Well if you use some aftermarket ECU then you could ignore this problem. Well anyway you will need bigger flywheel to hold s14 power. For example use it from m30 engine. I think that using m10 gearbox wouldn't be bad idea. Just put some "short" ratio rear diff.

Also original s14 intake manifold won't fit as probably there won't be a clearance between it and brake booster.



But biggest problem will be repairing this engine as almost all bits cost a fortune.

Good luck!

I have done a similar thing



In a race car so the same thing, engine mounted back to firewall custom engine mounts subframe modified to clear the sump. I use an m3 box but as it has an after market Ecu so I have a crank trigger set up on the engine crank pulley.

In a road car you want the matching gearbox as the ecu uses the fly sensors for the crank position. Stock engine mounts should work but you need to change the oil pan, you can buy one that is made for 02 conversion.

If you Google "e21 S14 swap", you'll find plenty of facts/opinions. Most of the stuff on S14s being put into 2002's is relevant as well.

Is it hard? I researched it for myself (for a 320 I had a while back) and gave it up as I didn't have the time or money. You can use the e21 gearbox, but need to modify it to fit the sensors (and then you have issues about handling the extra torque). You can use the M3 gearbox, but you'll need to modify your driveshaft (and transmission tunnel I think). You'll need to look at ECUs, cooling system, brakes, throttle linkages, electrics, fuel lines, etc.

It's an awesome project though, so I hope you can find one and get it done!

Cheers