M47 crankshaft to M42
 

Hey guys, I'm new to this forum, hope you'll accept me to your team, and help me navigate through discussions! Here's the deal: I have an E36/5 Compact with an M42B18, now the engine (along with the front suspension) was a total bust (head gasket blown, poor piston rings, dire need to change seals, differential, clutch etc.) so I decided to perform a major repair and also add some modifications if possible. So aside from the typical intake/exhaust mods, I have read a few topics about the crank change (m47) and a one-mass flywheel from an M20 installation. I live in Lithuania/Europe, so it's not to hard to find the M47 crank, but my main question is: what pistons (or a combination of piston heads and rods from different engines) should i use, to increase the displacement to at least 2.0l? And will the M20 flywheel just bolt-on fit with the standard M42 clutch? Please don't offer me to "simply swap an m50" because I really like the M42 (also the A/C that came with it :D) and I'm just wondering whether it could be improved. Also, it's almost impossible to find the S50/S52 pistons here so you can also scratch those off the advice list :D . Thank you for your time, I hope I posted in the right topic section.

The flywheel will bolt directly on the M47 crank. The crank needs a lot of work done to it so it will fit. The front snout needs to be cut off and then it needs a new keyway installed for beginners. It is not a easy job. Obviously you need shorter rods or better pistons with the wrist pin located higher on the piston for a better rod angle on the crank. Long rods good, short rods bad due to side loading of the piston on the cylinder wall. I do not have specs for rods or pistons but I think they have to be after-market. I might be wrong on the after-market stuff. I run a 2.1L M42 block with M44 head and M47 crank. It is not something you just throw together as I understand it.

Best, John Smith

Thanks for the reply! So I understood that the M47 crank still needs some work done to install, that's ok and thank you for the info! Also, I got my hands on an M44 block (with internals) and head. Would it be possible to swap an M44 head on an M42 block? What modifications need to be done and are there any gains? I've also read, that people use M44 rods with shaved (2.5mm) M44 pistonheads, to gain an approx 1996cc displacement, could that be true?

M44 head is a exact fit on the M42 block, There are advantages and dis-advantages. M42 head does not use rocker arms (I think) which is a plus by lightning the valve train. M42 head also uses larger head studs. M44 head uses the cam sensor so it can use full OBD-II function of the DME, M44 head can accept M3 head bolts which need to be shaved a little so they don't bottom out in the block before reaching full torque spec.

I have heard of shaving piston tops but my concern is that would take the top ring closer to the combustion chamber and cause heat issues on the ring and crown of the piston especially on a turbo motor.

If you are going turbo in the future you need the rings as low as possible on the piston to help remove heat created by FI and the additional power it makes.

endless hours of research
 

Hey guys, i have been doing endless and endless hours of research on how to make my M42 a stroker and a supercharger application. Im going to send my head into Vac Motorsports to have the stage 3 performance rebuild done, that includes: all the necessary machining, heat testing, balancing of new double coil springs and TI retainers, ect. http://store.vacmotorsports.com/vac-...ead-p1019.aspx. I am having my cams re ground by Dougherty Racing in Shingle Springs California, i have done some reading and the cams that are about $1000 are the same cams as stock just redone. The grinding is about $325 ( i will eventually buy brand new ones). ARP head studs (of course), new hydraulic lifters, all brand new timing chain, rails and guide, tension piston, bottom and top covers and seals. Thats my top end plan, now the bottom end is whole other world. I am getting custom JE forged M3 86 mm pistons with total seal gapless rings , high heat ceramic crowns, moly coated skirts, heavy duty wrist pins, contact reduction grooves, and double pin oilers. Would that be the best application for my pistons? Im thinking so. Arrow 135 mm Connecting rods, crankshaft and rod bearings, crankshaft main seals, ARP connecting rod bolt kit. I know my block can be bored out to 86 mm to increase my liter. The supercharge kit is from, http://www.koperformance.com/BMW/tur...harger_kit.htm. I cannot find a M47D20 crankshaft ANYWHERE i need help finding one for this to actually work correct. I would like to know some feedback on this plan, thanks guys. :smile:

Don't bore any more than you have to, it allows more heat to get into the water jacket and can cause easy boilover or raise cyl head temps if you get too thin, the small amount of power especially if your going forced induction is not worth it...

I assume you plan on some track time or similar with the mod list... On the street driven normally its not as important.

Dave

Hey Dave,
Yeah i figured that doing only the 86mm bore from the stock 84mm would be fine. Ill take it to my shop and see what they have to say before I have them do the boring. I plan on track time for sure, im gonna do coils, brembos, and a heavy duty control arm kit before i go out there. After the engine and break in i want to do a M3 tranny. I heard that the transfer case can bolt right up. I think im just gonna get my crankshaft machined brand new but to the specs of the M47D20 to handle the pressure in the bottom end and be able to just slide right in my block. Im gonna do all i can to the cooling system to make it run cooler like electric fans and cleaning up the whole block and pan, then painting them. Ive thought about mounting an electric fan on the inside of my hood and then having a hood scoop put in, anything to make this beast run cooler.

Yea, definitely sonic the bores heavily before the bore job.. Blocks are cast so the measurements are loose at best. I've had to go through 5 or six blocks to find one suitable for a +.080" bore on other engines...

Don't do an M3 trans, do a 330i/ci trans, the 6 speed is the same one as the M3 and since its not a "M3" part its way cheaper... ;)

Both of my BMW's are going to get waterless coolant in them on the next service, I'm tired of replacing under designed cooling system parts... Going zero pressure...

Dave

I replaced the whole cooling system when i started having overheating problems. I got a 375 berh radiator for only 175 from partsgeek and everything else. I plan on silicon vacuum hoses aswell because of how hot that damn engine runs, dont wanna have issues with that system.

How do you go about the water less cooling system? Can you do it even with a supercharger? Also with that 330 tranny, will it bolt up to the 318i transfer case? or will i need the trans case from the 330 also?

In your honest opinion, you think its worth doing a bore and stroke? or just doing a bore and getting my crankshaft reinforced and upgrading the rods and pistons still but keep the same stock stroke?

Waterless coolant is commonly used in heavy over the road trucks. Its a chemical instead of a glycol blend. It does not need pressure in the cooling system to stop it from boiling.. so less stress on hoses and gaskets. It replaces the normal mix with the change of modifying the pressure cap for 0 pressure.

No substitute for cubic inches! The bore and stroke will make more power. But the details of rod length piston type etc are the devil in the details.

There is no "reniforcing" of the crank it is what it is. One advantage of the M47 crank is its a diesel crank and is a heavier forged unit, much stronger than the gas engine crank.

The other issue is youll need a 100% custom burn on the ECU to handle a stoker + bore increase with out sending things off the edge. Adding the boost in will make it even more fun... :)

Cheers

Dave

Thats really interesting, i will have to add that to my plans as well. I did find some lengths for rods and what type of pistons you need to use to get that proper deck height without hitting the head. Im gonna use Arrow connecting rods at 135 mm and custom M3 pistons made at 86mm. Yeah i do know about that computer burning, can you suggest anywhere to get it done? Oh yeah i want to get the boost kit as well. Thanks for giving me all this new info and just touching base with me on it, it helps me futher understand what im getting into and seeing if its worth it. At this point im all in.

i just looked up, and yeah. you are right. the m44 head uses rockers and the m42 head does not. interesting.......