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Hewitt

M10B18 TO M20B20 CONVERSION

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Hi guys...

Just wanted to find out if anyone has done or know someone who did a m10b18 to m20b20 conversion?

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Don't.

The M10 is not, in standard form, a performance engine. Solid, reliable, and responds very, very well to forced induction, but it is an old engine and compared to most modern engines, heavy, uneconomical and slow. (In stock form.)

So is the M20B20. It combines the bad bits from the M10B18 and the M20B25 - it's bigger, a tighter fit in the engine bay, heavier, still not a performance engine by any means, and uses a lot of fuel. The M20B25 is a better engine in that it provides more performance, but other comments still apply. The M20 also responds well to forced induction (in particular).

If you feel you must change the engine, look for a simple swap like a M4x. 16 valves, perkier performance, better economy, and still provides a tuning route should you wish to go that way. I'm still keen on the idea of a M43 in an E30 (fantastic economy, good performance in a lightweight car like an E30, simple) but I'm just a bit odd like that. 🤪

If not a 4-pot swap, there are much better (and very well-documented) 6-cylinder transplants. M54s are popular for good reason. However, any 6-cylinder engine (imho) spoils the natural balance of the 4-cylinder cars. There's a good reason why BMW stuck with a 4-cylinder engine for the E30 M3 rather than develop the M20 engine for racing.

Edited by gjm
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^^yup, what he said.

if you want to do an engine swap pick anything other than the M20B20, just not worth the effort.

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Thanx for the advice guys but the problem is that i already bought the M20B20,already in the car.

This conversion is basically a starter pack for me as its the first BMW for me.I used the M10b18's flywheel and starter but having issues with the starter.

 

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Ahh ok, previous stuff not too relevant then, sorry.

What is the starter problem, is it spinning but not engaging on the flywheel?

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1 hour ago, Hewitt said:

This conversion is basically a starter pack for me as its the first BMW for me.I used the M10b18's flywheel and starter but having issues with the starter.

The M10 starter is unique to the M10 engine, but whether that is because of the flywheel (which you've used) or for another reason I couldn't say without a lot more investigating.

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Is the M10 ring gear the same diameter as the M20?  I don't know if they are the same or not, but something to check.  If the diameter is close but different then the starter may be in slightly the wrong position  with respect to the ring gear when installed into an M20.

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Yip,i think ill start with the starter before removing the gearbox again,coz when the starter is tightened the engine does not turn but when the starter is a bit loose,not fully tightened,it makes a grinding noise....thanx for the advice guys

.

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