M20 Engine Build Options

[e21Keith]

So I rebuilt the engine in my 323i as part of the resto but it's gone all rattly so I need to start again. Can anyone help me with what the options are using the original B23 block?

I could go stock but my bore on #6 doesn't look so great, I'm into around £1000 for linering and standard pistons or I can have oversize pistons made at about the same cost, this isn't very appealing!

Help please with alternatives? I have a 324d crank (same as the ETA but forged), and a whole selection of B20, B23 and B25 parts, so I could go for a larger capacity. I want to keep the car at least looking stock so the original numbers matching block plus the K-Jet. What combination of crank/pistons/rods can I use, what capacity could I end up with.

Sorry this is such a woolly question but I don't really know what the options are or where to start?

[e21Keith]

OK, nobody knows the answer to that one!

So I'll probably have to go stock which means a new set of pistons. Ireland Engineering list these for the e30 but not for the e21, and upon checking the ETK I find they have different part numbers.

Does anybody have experience of having pistons made by Ireland Engineering or indeed anyone else?

[Jeroen]

Uwbuurman may be able to provide some info on this

[uwbuurman]

Well, we do have a 2.7 topic in the pinned tech topics. I'll try to write some stuff up, tomorrow

[Duracel79]

There are some many different ways of skinning the M20 cat. none of them really cheap.

Using your 81mm crank would need the block boring out to ø84mm and pistons & head to suit.
Then depending what CR you are happy with or what pistons you use, decking the block and a vernier cam gear may be needed.
To use your 200 casting head and the Diesel crank would need ETA pistons (or new custom ones).

There is a lot of info around about M20 build just have a search.

HTH

Ben

[e21Keith]

I think I might have found the answer to my engine rebuild conundrum, a NOS rebuilt short engine, rebored with new genuine oversize pistons. It will take a while to be delivered.

[Jeroen]

I'm used to cars with more horses, but in my E21 I'm quite happy with the stock 2.3 setup. There's always something that's faster...

[e21Keith]

I have 8 horses in the stable and they all have more power than my e21. The e39 M5 is usually enough to satisfy my need for power

[Jeroen]

[e21Keith]

At last the engine is back from the machine shop, only took them three months!

Now I have 6 new pistons at first oversize, one of the bores still needed a new liner, crank is also at first oversize. The head was done not that long ago because the original was cracked, this time I'm adding a new camshaft and all new valve gear.

Today I started to remove the engine from the car, taking it with the gearbox. Everything is removed from up top, tomorrow I'll get underneath, I expect to pull the engine on Saturday.

[Jeroen]

Good news, swap time! Pictures please!

[e21Keith]

After some problems with parts suppliers:
Recon PAS pump took 2 weeks to arrive.
New rockers took 2 weeks to arrive, when I fitted them 2 looked the same but the hole for the shaft was too small.
Wrong oil filter supplied.
I started the engine for the first time yesterday. First issue during startup was dumping the contents of the sump due to the incorrect oil filter (luckily before I started the engine). It's all quiet, so I'm happy. Need to adjust the timing and mixture.
Need to refit the bonnet and book an MOT, then I can drive it for the first time in nearly 12 months.
The list of new parts (excluding the obvious gaskets etc).

New Oversize pistons
Camshaft
Rockers + eccentrics
Camshaft spray bar
PAS pump
Injectors
Radiator

Machining work
Rebore to first oversize + liner for cylinder no6
Reface block
Chemical clean block
Crank was reground to first oversize

This is in addition to the machining work on the head at the last rebuild.

[Jeroen]

but you got there in the end!