Differences between E30 m42 engine and E36 m42 engine

[DoctorDrift]

Hello guys i have a question regarding these two engines.....

I own an e30 318is which i use as a daily driver and a sprint/hillclimb car. The current engine has done 175k and still going ok but i want to do an eaton supercharger conversion. As i use the car as a daily driver i want to build the new engine with supercharger up in the garage over the winter ready to drop in over one weekend. Therefore i need to get hold of another m42 engine. Here lies the problem.... i cant seem to find any e30 m42s for sale but ebay is full of e36 m42s.

Are there any major differences between these two engines or not? They look almost identical except for the different manifolds and some other subtle differences. I have read they are the same block/head which is all im really worried about but want a definite answer really before i shell out for one only to find its different or worse go to put it into my car and find it doesnt fit.


Any help would be much aprreciated guys.

Thanks

[rix313]

Welcome

If you check the sticky thread in this section it names the main differences between the engines and what you need to do to fit an e36 M42 to an E30. E30 M42's came with forged crank and rods, this was phased out in the E36's and the M42 was only used up to 1995 when it was replaced with the 1.9 M44 which is different.

If you're looking at building an engine from scratch, something I was looking into for my Rotrex build was a low compression engine. This can be done with special pistons but some clever chaps on here worked out for me that it can also be achieved by building a 'hybrid' engine built usuing parts from the M42 and M44. The combination was an M44 block and pistons using an M42 crank and rods this gave a CR of around 9:1 down from 10.1:1.

I've got a spare M44 and M42 in bits and a Rotrex super charger kit for sale if you're interested ;)

[DoctorDrift]

thanks for gettting back to me its much appreciated.

I saw your rotrex kit for sale, very nice just wish i had the cash. I will have a think about it

Only problem with using the m44 block is that regulations for the road going class which i run it state it has to be the original block so it has to be m42 block. Surely it wouldnt be too difficult to deck the block to lower compression though would it?

Basically as long as the e36 m42 block/mounting points and head is all the same i will just get a e36 m42 i think as there are loads around.

I was also toying with the idea of boring out to 2l and going doing ITBs/cams/headwork/ecu but supercharging seems like the easiest/cheapest way to 200bhp. PLus the lovely torque delivery of a supercharger, oh and the whine

[rix313]

What are you allowed to do on the piston front? We (we being them clever people no me) did also look at M54B30 pistons which are the same size as the M42 ones but have a lower crown height and gave a lower CR. The arguement that arose was the fact that the M54 pistons were totaly flat where as the M42 pistons have quite a large bowl and that the flat pistons wouldn't suit the design of the rest of the engine. Are you able to bore the block? You could look at boring it out for M44 pistons?

What are you running the car in sounds interesting

[DoctorDrift]

Im running in a local MSA sprint and hillclimb championship under the regulations in the MSA blue book.

Basically you can mod the block providing its the original block so all internals are free and you can bore as close to the oil/waterjacket as you dare ha ha

Induction is free but blown engines are subject to a 40% cc increase so you go up a class. i want to either go 2l NA or 1.8 supercharged so that would put me in the road going 1800-2600cc class where i think i can be competative. I wouldnt want to go 2l and supercharged as that would put me into the over 2600cc class = me getting my arse whipped by imprezas/evos. I just want to put one on all the mk1 and 2 escorts really

I am very intrested in your rotrex setup after thinking a bit more today. Basically everyhting is included in the kit appart from an ECU right? what ecu were you thinking of running? I guess with forged pistons i would basically have a forged engine and could then run some fairly heavily boost. What bhp were you looking at running? im just not sure at this stage whther Rotrex would be a bit overkill as an eaton running about 200bhp should be enough for me to be competative in my class.

[rix313]

Where in this wondering country are you then?

Bar a few fiddly bits like a bent dipstick tube, fuel pipes and maybe some other bits I've overlooked (and I can't think of any) yes it should all there. Of course you would need to do some work to bolt the intercooler on and cutting some metal away from the valance so it doesn't rub on the paint work etc. The build thread for it is in the forced induction section and as I've gone along I've done my best to document and explain everything. Besides that I'll happily talk you through it should you have any troubles.

I was only looking at running 200bhp from the Rotrex but the way I was looking at it was the scope to go further and do more is there waiting to be unleashed. Like I say I was looking at building this hybrid low comp budget engine in order to get more power from it with relatively low cost with out going made on custom low comp forged pistons.

[DoctorDrift]

Ive had a look through the build then you mention and its looks very comprehensive. Fitting the intercooler etc shouldnt be too difficult like you say and any other little bits and peices should be ok. hmmmm very tempted......

I will have a think and explore all the options etc and let you know if im willing to make you an offer

Im living in Truro, Cornwall and the events i participate in are mainly in the southwest. Unfortunately though one of the regular sprints in the area wont be happening anymore after 50 years! its a pain, the MOD want to sell the airfeild it happens on. Such a blow for Cornish motorsport. Anyway, rant over but it does mean i might have to venture further up the country to get my kicks

[rix313]

Euro millions -> buy super charger > buy airfield = happy days lol if life was that simple.

Quick buzz up the M5 and you have Wales to play around in I suppose. I'm up by Castle Combe which is obviously handy for track days but there's lots of airfields here where you can do cheap track days which are good fun

[DoctorDrift]

Yeah there was talk of the Club buying up the airfield but then membership fees would be insane for the next 10 years trying to pay it off. We should be able to sort something out though.

I have been thinking about coming up to castle coombe for a track day and there are some good events up there like you say. Its just all extra money isnt it thats the problem. Need to get a towing vehicle and a trailer then i will be laughing

So what are you running in your car currently?

Ive been thinking about the ITB situation and as nobody really makes a specific kit for the m42 bar dibilas an ITB set up will need custom fabrication. So what about using bike throttle bodies and fabricating a manifold? Jenveys arent cheap and you would still need a manifold. Any thoughts?

[Brian28]

I got the manifold flange made up by a mate, then sent flange and carbs to Grantley (zone username) who made up the runners for a very reasonable price. Would be much the same set up for bike ITBs, and a shed load cheaper than Jenvey or similar.

[rix313]

I've just been doing track days and working on this super charger but my job is as a race mechanic so spend most of my time at race circuits. I've started to get a little bored of not being the one having the fun so want to try squeeze some TTRS races in next year if I can

E36 M3 throttle bodies can be made to fit with a bit of fettling, not sure what gains you get from it though.


There's a PM sitting in my outbox for you Brian is your PM box full?

[Brian28]

There's a PM sitting in my outbox for you Brian is your PM box full?

Sorted now

[DoctorDrift]

hello brian thats a nice little setup youve got there nice one.

What size bike carbs have you gone for then? ive had twin webbers o previous cars ive owned with great results and the then sound is awesome.

Whats the spec of your engine with those then and how does it run? I have always fancied trying bike carbs out too. So many options.......

[Brian28]

http://www.e30zone.net/modules.php?name ... sc&start=0

[dsm2002]

Other differences: From 9/92, E36 M42s have 6mm valve stems, E30 valves have 7mm stems. E36 have single valve springs, compared to doubles for E30s. E36 retainers also are lighter: about 12g compared to 19g for the E30 retainers.

E36 valve train


E30 valve train