e21 m42 convertion

mr edd · Post by **mr edd** » Sun Jul 31, 2011 7:05 pm

I am thinking of bringing my car up to date and giveing it a bit more go to boot and seen as i am a 4 pot fan this seems an ideal engine to swap too ...Can anyone offer any links to technical based threads or sites that could give me an idea what needs to be done to fit one of these engines...edd..

e21-Mark · Post by **e21-Mark** » Sun Jul 31, 2011 7:59 pm

I've got an M42 in my track car and personally I think it really suits an e21. I believe it's just 323 mounts and an altered sump & pick-up pipe to get it in. Plus modifying the exhaust manifold. I must admit, I don't think the engine sits at an ideal angle though as it's not level as it is in an e30. Mind you, it's been OK so far.

If you were nearer I'd suggest you came and took it for a spin so you can see how it goes for yourself.

drjim · Post by **drjim** » Sun Jul 31, 2011 8:30 pm

6 pot gearbox needed too.

M42 is heavier than an M10, and produces 140-150 bhp. Rebuilt 2L M10 will do the same. Only thing going for the M42 is that if it goes pop there's loads more out there, whereas M10's seem to be getting scarcer now. Depending on a few things I might know where there is a 150ish BHP M10 available.

e21-Mark · Post by **e21-Mark** » Sun Jul 31, 2011 10:30 pm

I think there's a fair bit more torque available from an M42. Personally I like the way they rev compared to an M10 too.

How much heavier is an M42 Jim?

I'd like to have my M42 on twin 45's or ITB's might be simpler?

Jason_323i · Post by **Jason_323i** » Sun Jul 31, 2011 10:37 pm

carbs on a m42 could be easy ,manifold of the shelf, use them with a TPS so you get the stock ignition to work? or use megajolt

Jason

e21-Mark · Post by **e21-Mark** » Sun Jul 31, 2011 10:46 pm

I like the idea of a twin-cam on 45's. I may have to look into this. I wish I'd grabbed the cheap Alpha N I was offered.

Seems like 200bhp is easily available with a super-charger. Now that would be good fun.

mr edd · Post by **mr edd** » Sun Jul 31, 2011 10:52 pm

forgeting the speedo situation how good are the getrag 240 boxes from a e30 ? Are they weaker than than a e21 box as i would be looking to use a e30 box to keep the engine at the correct angle and make engine mount to suit...i would like to make the car look stock 1975 but with a modern engine/power steering /5 speed gearbox sort of old but driveing like a modern car...edd

e21-Mark · Post by **e21-Mark** » Sun Jul 31, 2011 11:07 pm

I'm told they're plenty strong enough although never had one myself.

Am I right in thinking the M44 1.9 is the same externally? Is it better for the extra displacement?

Another plus point about M42 as opposed to M10, is the all steel forged bottom end. I guess that's why people readily supercharge them?

I also have a set of BMW bike ITB's that only cost £12 and still have TPS etc. Bogg brothers do an inlet.

mr edd · Post by **mr edd** » Sun Jul 31, 2011 11:49 pm

I think the m42 and the m44 are almost the same externally . I am told that the m44 has one sender opening in the head and the m42 has two for the e30 ecu which is something that can be sorted ...I was collecting parts to convert me e30 316i to m42 power but last weekend my sister sold me her e36 318is for peanuts as the engine had a serious water leak following a ultra light knock by another car (cost £7.75 to fix!) so the project e30 was scrapped minus all the e30 318is bits i had collected to date(ecu/ rad/sump /starter/spare gearbox / fly wheel /clutch ect) and i got more money for the lightly stripped e30 than my sister asked for the leaking but taxed/tested e36.....funny old world isn't it!....edd

e21-Mark · Post by **e21-Mark** » Mon Aug 01, 2011 12:01 am

It certainly is.

I do like M10's but I do like the characteristics of the M42 more. I know my track car is lighter but with the close ratio box it goes really well and still has all the nimbleness of a 4 cylinder car. I didn't realize the bottom end was all steel forged but it explains how it's coping so readily with the abuse it gets on track. It does love to rev! Sounds great too. I've been looking for the dyno sheet but iirc it was around 154 brake.

Jason_323i · Post by **Jason_323i** » Mon Aug 01, 2011 12:09 am

M44 is a budget M42 (plastic thermostat housing rather than alloy etc) different type of head (plastic thermostat housing rather than alloy) and for some reason not as tuned.

M42club has loads of info

Jason

tommi_e21 · Post by **tommi_e21** » Wed Aug 03, 2011 9:50 am

get a 2 litre diesel crank from a rover 75. a hartge m42 spacer plate and whoop bang 2.3 twin cam. budget M3

think you can put solid lifters into a m42/m44 aswell and as the internals are forged (i think) then you can rev the tits off them.
i still prefer M10's. (KISS Keep It Simple Stupid)

rob0r · Post by **rob0r** » Wed Aug 03, 2011 11:06 am

I had an M42 hanging briefly in my 316 engine bay. The box from the E30 M42/M40 engine fits fine and only needed slight ovaling of the gearbox cross member bolt holes to fit from memory. The E30 318is prop can be used if you make some prop centre mounts further towards the back of the car and if you take the nut off the sliding joint (not needed).

Engine mounts are DIY, I don't believe 323i mounts fit but it would be great if they did - do you know this for sure Mark? Photos?

To be honest I would be trying to track down an E21 6 pot box for the speedo input, there are rumours that this may become a part of the MOT in the future - though Murran might have a better idea if this is rubbish or not. Also I wouldn't be too worried about keeping the sump flat and rotating the box instead, modding the linkage and box crossmember wouldn't be hard.

My 316 will be going back to M42 as I've just had a nice chipped engine come in. Have some pics from the good old days!

E30 box and crossmember

I converted the M10 subframe to take the standard 318is engine mounts. This time round I'll probably make mounts to fit the subframe instead

mr edd · Post by **mr edd** » Wed Aug 03, 2011 11:20 pm

wizor do you have a link to your thread on retro rides that the pictures came from ? I have been trying to find your thread for ages but can't for some reason...I think i will test fit a e30 m40 engine and box that is in my lock up so that as soon as i buy a m42 motor all the fitting issues should have been sorted ( propshaft /engine mounts/rad mounting..ect) ...edd.. p.s. m42 to m20 engine how many degrees is the engine tilt different by ?

rob0r · Post by **rob0r** » Thu Aug 04, 2011 1:17 pm

I'd be tempted to wait for an M42 engine to be in the bay to be honest, the head is twice as wide and although the clearance is OK the exhaust will be in a different place etc etc. The only benefit I can see is for engine mounts to fit an M40 first.

M20 to M42/M40/M50 tilt is quoted between 10 and 15 degrees, I'm not exactly sure. I mounted my M50 with M20 engine mounts and gearbox, so the engine sits at the M20 angle, the sump hangs low but I've not smashed it yet.

http://retrorides.proboards.com/index.c ... 272&page=1

Or the duplicate thread on here
http://www.bmwe21.net/forum/viewtopic.php?f=7&t=1895

bmwe21.net forums

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