M20B25 to 2.7i cylinder options

[ramerco]

I am planning a rebuild of my m20b25 with new head gasket, rings, and bearings. I am currently thinking about swapping to an 84mm M52 crank and 130mm rods from an eta and a cam upgrade (maybe a 272). I know people suggest custom cylinders. I am going for a clean reliable street/cruising build. Nothing for the track. It will be mated with a 2.93 LSD diff, so I am looking for a boost in low end torque with the taller gearing.

I've looked here: https://www.r3vlimited.com/board/for...ow-to?t=100939 and many other places really, and still have questions.


1. Will I need alternate engine control unit if i have a 173 ECU already? Are there performance chips available for stroker setups or do I need something totally custom?
2. What piston suggestions do people have with the m52 crank/eta rods and a 272 cam. I am looking for pretty high CR since I am staying NA. I've seen suggestions that the standard 325i pistons will be fine
3. When do I need to worry about an adjustable timing gear with a cam upgrade?
4. I've also seen that the m52 crankshaft needs a spacer. Can anyone suggest a source for that? machine shop? I've seen this too: http://metricmechanic.com/engine-parts/ Is that all that is needed for this crankshaft? Everything else stock?

[ramerco]

Answering most of my questions with this thread - https://www.r3vlimited.com/board/for...50#post4609050

just took a while to find right thread..

[digger]

- stock b25 pistons and machined skirts or cut crank
- crankshaft sleeve plus longer bolt from 24V engine and modified/ thinned washer. MM sell a kit with the three parts (there are cheaper options around)
- top of block needs to be machined off a bit, like 0.5mm give or take to get the squish and compression optimal
- a chip will work in the 173 but make sure its running well stock otherwise you'll be chasing ghosts, it'll run ok off the bat with a modest increase in injectors and stock chip.
- stock cam gear will be pretty close if you dont have the funds for 200-250 for one as its only 0.5mm off the deck, its obviously ideal to set the cam correctly though.

[ramerco]

Thanks for the reply. I do have a good set of stock injectors, with good matched flow. If I don't do anything to the head, other than cleaning it up, and just do the crankshaft/rods, I think I should get what I am looking for. I'm not craving more power up at the top of the band really, so after reading more it seems like the camshaft might be overkill/not in line with what I want to achieve - which is simply better pull from low-ish RPM to match the 2.93 diff for regular driving. Not to mention custom camshaft is a big expense relative to the overall budget. Seems if I just do the crankshaft and rods with the required piston mods/decking to fit it, i should get smooth running engine with up to ~190+ lbs of torque. Should be plenty improved to feel it over the aging ~145 lbs from the stock engine.