Hello M42 newbie is here

[e34biturbo]

The 10:1 compression is a big part of the difficulty, for sure.  Pistons could fix this.

The thing I wonder is: the M42 can only be overbored to gain ~+150cc's max.  Being that there is not much material between cylinder bores/thin water jackets, a really high boost motor could see some serious failure.  I am not very knowledgeable about FI system building though, so this may just be my engineering background making me scared.

Hmmmmmmm Compressionwise I plan to go no lower than 9 0 1......so eliminate the dogginess of the 4banger....add some good internals and hold on tight....I would not over bore either motor....need that meat for the heat and friction...

I might just try a stock motor 1st to see what is what then when it blows rebuild it ..........

[thumper3ld]

Hmmmmmmm Compressionwise I plan to go no lower than 9 0 1......so eliminate the dogginess of the 4banger....add some good internals and hold on tight....I would not over bore either motor....need that meat for the heat and friction...

I might just try a stock motor 1st to see what is what then when it blows rebuild it ..........

I've heard you can run 6 or 7 lbs of boost on a stock m42 motor. I plan on trying the same thing and seeing what happens. But if you want to try first, then please, be my guest.

[e9nine]

I might just do one of each motor......
but the M10 is sounding like my dream....baby SOHC:D
well pockets are not an issue we will be doing most of the work 98% with pics as with all the others.......this will be my debut tuning the engine with the DTA all by myself no help....I feel the M42 will be able to make 500 to the wheels......the M10 similar......so let the games begin!!!!


Oh talk to me about the tranny variations.......

I got an E30 2.5l tranny and an E36 2.5l tranny.......

Do up an e30m42 turbo. We get no love. All talk no show with most boosted m42s in the USA.

Tranny failure hmm...Getrag 240 hasn't been pushed far by most. Check out this dude's page http://www.ticco.com/318tic_e.html and look under 2002 to see what he had done in the past with his m42 before going with an m20 .

He ended up with " About 250+ hp. Original 10,0:1 compression. (not safe!) 325 (3,73) differential." as his final numbers when I PM'd him ages ago about his set up.

His site isn't in full english and kinda hard to navigate but u can see what he did with the basics.

The Getrag 240 can be used for m/s50 conversions (but very few choose to say with it) so perhaps a getrag 260 can be mated to the block as well? Sadly you might have to do a lot of trial and error but the good thing is you already have the other trannies handy. It's just the mix of the flywheels and pressure plate along with throwout/pilot bearings and slave cylinders that will get interesting. I don't think driveshafts *might* not be too much of an issue. If you do stick with the getrag 240 you can use the m20b25 flywheel with modification to the starter pinion gear and use a 323i pilot bearing.

When you get your project started others will obvioulsy chime in to help out as much as possible. I don't do turbo stuff - I just appreciate the hard work and try help as much as I can with moral support

[bmwman91]

Tranny-wise, zerofrez on here works in a shop and says that and tranny from an S/M5X family motor bolts right on, since the M42 is essentially one of them missing 2 cylinders.

My cylinder-wall concern was not due to boring it out, it was that there is nto much meat in there to begin with.  Now, I am not at ALL saying to not try it.  The though of one more already-rare M42 going south does nto appeal to me, but my curiosity is even stronger!  Dooooo iiiiit!

[Febi Guibo]

the M42 can only be overbored to gain ~+150cc's max.

for N/A applications this isn't quite true... just an fyi.

[bmwman91]

Interesting...what IS the max displacement increase an M42 can reliably undergo?

[e34biturbo]

I've heard you can run 6 or 7 lbs of boost on a stock m42 motor. I plan on trying the same thing and seeing what happens. But if you want to try first, then please, be my guest.

I plan to blow them both

[e34biturbo]

Tranny-wise, zerofrez on here works in a shop and says that and tranny from an S/M5X family motor bolts right on, since the M42 is essentially one of them missing 2 cylinders.

My cylinder-wall concern was not due to boring it out, it was that there is nto much meat in there to begin with.  Now, I am not at ALL saying to not try it.  The though of one more already-rare M42 going south does nto appeal to me, but my curiosity is even stronger!  Dooooo iiiiit!

so the M10 should in theory be able to use a 260/265 box

[Febi Guibo]

Interesting...what IS the max displacement increase an M42 can reliably undergo?

I'm at a little over 2100cc...

[bmwman91]

I'm at a little over 2100cc...

2100...that is stoked AND bored right?  Any idea what the max displacement with just an overbore is?

Overbore it and turbo it, if you are gonna blow it up anyway!

[Febi Guibo]

my non-scientific opinion is that for f/I spplications, you could take it out to S50 size pistons... around 86.5 mm or so....