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bmw e30 m42 engine build and ballance

44K views 57 replies 10 participants last post by  _Ethrty-Andy_ 
#1 · (Edited)
recently torn apart my m42 engine due to profile gasket failing and decided to take the oppertunity to re build with new rings, bearings, gaskets, seals etc. also decided to have the crank balanced and single mass flywheel lightened, which will be done this week hopefully. with pictures to follow.

so far recently just had cylinder head skimmed, valves re seated, fitted new valve stem oil seals and chemicaly cleaned. :)

as for the block iv checked all the oil clearances on the crank and rod bearings with plastigauge and were all within the tollerances except slightly more wear on the crank bearing nearest the timing chain.

cross hatch could still be clearly seen on the cylinder walls which tells me their has been no problems with over heating or excessive wear.

next week ill be getting the crank balanced along with rods pistons, flywheel and clutch.
having the clutch lightened.
setting piston ring end gaps and assembling bottom end and fitting pistons.

HAS ANYBODY ANY SUGGESTIONS ON HOW MUCH WEIGHT TO SHAVE OF THE FLYWHEEL?
DONT WANT IT STALLING ON GEAR CHANGES BUT WANT THE ENGINE TO REV EVEN MORE FREELY. NOT THAT IT REALLY NEEDS IT BUT WOULD REGRET NOT DOING IT WHILEST THE ENGINE IS OUT.
 

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#34 ·
Thanks for the comments.
as for the throttle bodies they will be exposed. look so cool!
as for tunning im just goin to experiment with fuel pressure and maybe try some different injectors with slightly better flow rate.
will then at some point have the car dynod for fine tunning.
would of been nice to do away with the flap type air flow sensor but from what iv herd theirs no advantages other than looking neater and would cost alot of money.
 
#40 ·
bmw m42 itbs

hi guys, you are right about the airbox design, the air flow will be slightly more restrictive for cylinder 1 and 2 but the airbox just seems to work fine, it was going to be just a tempory thing so i could get the car running with the maf. idealy the inlet wants to be centred between cylinders 2 and 3, maybe ill get around to make another one soon.

at the moment im playing about with the runner length as their is plenty of power mid range but want the power up high so the runners are going to be shortened to a similar length to those on the s52 engine.
cant believe you thought i would just leave the air box looking ike that.
 

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#42 ·
Props to you for adapting the ITBs and building your own intake. You are more successful than 99% of those who dream about it - including me!

So how did you adapt the ITBs to the intake ports given that the M42 intake ports are shaped differently from the ITB ports?
 
#43 ·
itbs

thanks again for the comments guys. to adapt the itbs to the runners from the cylinder head they were a pressed in fitt with rubber gaskets. only by chance did the throttle body fit very snuggly into the aluminium tube. i know that idealy the aluminum runners should be tapered from the itbs but hey.

could do with some help actualy, iv been having a few problems with setting up the tps and cant seem too get it set right. depending on how i have the tps it either cuts out at 2000rpm then picks up suddenly or if i have it adjusted the other way it limits at around 4500 rpm frustrating!

the car is soooo much more powerful till it hits 4500 then its just really slow. i really dont think its the length of the runners or the itb size not alowing enough air mainly because of the amazing amount of power so low down. i can only think the problem is a result of the tps.

tomorrow im going to get a battery for my multimeter and test my tps.

any help would be appreciated as maybe im overlooking somethin really obvious.
 
#48 ·
pressed in?

thanks again for the comments guys. to adapt the itbs to the runners from the cylinder head they were a pressed in fitt with rubber gaskets. only by chance did the throttle body fit very snuggly into the aluminium tube. i know that idealy the aluminum runners should be tapered from the itbs but hey.
Sorry for the many questions but I'm really interested in how you did this. I can't quite picture what you mean by "pressed in with rubber gaskets". Can you give us a pic of the itb setup from the intake side?

I'm not sure if I read it correctly but it seems to me that you had to reshape the itb and keep the join sealed via rubber gaskets. Am I right? What tool did you use to press the itb in?

Is the intake port spacing 100% correct or did you have to fix that as well?

Thanks!
 
#44 · (Edited)
fixed

got to the bottom of the problem, was the injectors that was playing up so switched them for some spares and they work fantastic. the car definatly feels up on power id say iv gained at least 10 bhp and more low down torqu but its difficult to say exactly without a dyno but it was definatly worth all the effort. the sound is just amazing!
also recently bought a magnex back box for a 10er and the sounds great.
really lovin everything about the car.
 

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#45 ·
got to the bottom of the problem, was the injectors that was playing up so switched them for some spares and they work fantastic. the car definatly feels up on power id say iv gained at least 10 bhp and more low down torqu but its difficult to say exactly without a dyno but it was definatly worth all the effort. the sound is just amazing!
also recently bought a magnex back box for a 10er and the sounds great.
really lovin everything about the car.
Great work. Do you have plans for a coil-on-plug setup?
 
#50 ·
m42 itbs

hi mmmm7, ill get some pictures uploaded soon for ya to have a closer look.
to try and describe it better the outside diameter of the itb is about 38.5mm and the internal diameter of the aluminium runer is 38mm so i had to heat up the aluminum runner so it would expand anouth to press the itb into it. i also used a rubber o-ring to seal the end of the runner to the itb. it didnt realy need the o-ring but fought i may as well give it try.
also the spacing is exactly the same as the ports in the head.

i dont know if your intrested but i was thinking of making a couple sets up to sell.
if you was to be intrested i could make the the adapter plate with runners and the itb set up for around £250 plus postage. all that you would be left to do would be to make your own airbox. or i could do for an additional £70.

all i can say is id never go back now, the car revs like bike the rev counter can hardly keep up and theirs a definate power increase for sure. i know u probable would like to see a dyno chart but they work really well.

in my honest opinion id say its a given 5-10 bhp
 
#52 ·
Now I get it!

The pictures combined your patient description of the setup really cleared things up. The throttle bodies are connected to the stock intake runners, correct?! Sillly, silly me. :rofl:

I was coming from the perspective of having the throttle bodies bolted directly to the head ala the S54.

I am intrigued by your setup. Would the same work for an E36 M42 but using the E30 M42 runners?

Would the adapter plate you're planning to build be placed between the stock intake runners and the throttle bodies?

I am looking for a good solution to incorporate ITBs on the stroker M42 I'm planning.
 
#53 ·
m42 itbs

iam not to sure about it fitting the e36 m42 engine but id imagine the head plate being the same. the only problem i can see you having is the variable intake motor and electrics, iam only guesin that if you did disconect that the engine wouldnt start, but if it would still run without that connected i cant see it being a problem doing itbs.

my brother has a e36 m44 which is basically the same as m42 as you probably know.
and we will be doing a similar setup for his. iam sure that their will be away.
 
#55 ·
m42 cracked head

bit of bad news today, the car started to overheat and has cracked the cylinder head round a exhaust valve into the water jacket. bit peeeed of about this after all the time spent on it.
i think it was the theromostat that wouldnt open that made the engine overheat. cant be sure tho. :tsk:

so now im lookin for a m42 cylinder head if anyone has one for sale?

over option is to sell the engine without the head and look into doing a m54 engin conversion. will have to price up first tho.
 
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