quad cam m70

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quad cam m70

Postby g73a » 10 Jul 2016, 22:21

i thought i would post a little thread about an engine i'm building.

from the research i've done, it seems a few people have attempted to retrofit twin cam heads onto the m70 block before, from what i've found, only 1 person has actually produced a running engine.

the ultimate goal is to have a running quad cam v12 with a manual box, fitted into an e46 coupe. clearly that's a long way down the road right now.


for a little bit of background, the m70 is a 5 litre, 60 degree v12, with an alusil block and single cam heads. the heads have extremely restrictive ports as the engine was designed to provide lots of smooth quiet torque, rather than outright power.

the s70/2 ( think maclaren f1 and bmw lmr) is very loosely based on the m70, with a pair of twin vanos s54 (e46 m3) heads and lots of other shiny goodies fitted.

i want to build a bit of a halfway house, unfortunately s54 or ever m54 heads dont fit onto the m70 block. however m50 heads do.

im doing this purely as an engineering exercise, just to see if i can. i know i could go out and buy an n73 off ebay, but that would be boring.


this thread is mainly just going to be pictures of random bits of engine, but my basic spec so far is;


m70 block - dry lined with iron liners but keeping the 84mm bore.

m50 heads - obviously one needs to be a mirror image, i'll cover this later

m50 cams, valves ect..

m70 crank - stock

m44 conrods

m54 pistons



that's it really.

so basically the first job is to make the "right way round" m50 head fit onto the m70 block .

http://i1064.photobucket.com/albums/u36 ... mrkfog.jpg

the stud pattern is the same and the coolant passages line up fine.

the oil feeds are completely different, so the standard oil feeds in both the block and head will be capped off and the oil fed from else where. there are two oil feeds into an m50 head, one in the centre (length ways) feeds a main oil gallery running front to back down the head. this feeds all of the cam journals and lifters bar the front ones. the second oil feed, supplies the front journals (which double as the thrusts) and both chain tensioners (the crank to cam chain and the chain between the two cams)

the main head oil gallery breaks out the back of the head with a blanking plug, this will be replaced with a banjo bolt and the oil fed in from here, through a check valve (to prevent the head draining after the engine is stopped)

the second oil gallery is a bit more tricky, the plan here is to mill as slot in the face of the head and weld a tube into the slot. the tube will break into the original feed gallery and will terminate at the other end with a jic fitting somewhere around what was the thermostat on the front of the head. the channel will then be welded up and faced flush.

the coolant flow will be slightly different from standard, due to packaging reasons. the coolant will enter the block in the centre of the V, through the front timing case, flow between the v, out the back and back into the main section of the block, flowing around the cylinders and through the deck, into the head. it will then exit the front of the heads through what was originally the thermostat housings. alternatively i could flow the coolant the other way round (which i think they did in the m52/54?) the coolant pump will be electric and remotely mounted so that's a flexible option.

because i've cut off and blanked the original coolant exit (clearance issues between the 2 heads) ive re-purposed what was the thermostat housing and cut that through to become the main coolant exit.

http://i1064.photobucket.com/albums/u36 ... h8z0qa.jpg

http://i1064.photobucket.com/albums/u36 ... ctc92g.jpg

with those mods done, the bank 1 head is just about finished.

there are extra oil return holes in the block compared to the head, so i just knocked these up to blank them off.

http://i1064.photobucket.com/albums/u36 ... bmneai.jpg

the oil returns dont quite line up so i solved that by opening them up slightly so the block now matches the heads.

http://i1064.photobucket.com/albums/u36 ... zrlfh7.jpg

the bank 2 head is a little more tricky, but in short, i'll cut both ends off, turn the middle 180 degrees and weld the ends back on. theres a fair bit of jigging and post weld machining to do, in order to make sure everything ends up back where it should be.

once that head is done, i'll work on the cam chain drive. the original m70 uses a single chain in a triangular loop, with a bridging piece between the two heads. i dont like this, so im going to do something along the lines of the way most other v engines work; a loop up one bank, down back into the v, up into the other bank and back to the crank.

i've started drawing up a new front timing case for this purpose. i need to get the original case on the cmm and pick up all the hole centres properly, but this is close enough for now. it allows a double chain run up both banks and deletes the mechanical water pump.

http://i1064.photobucket.com/albums/u36 ... bpixel.jpg

for induction, i'll use itb's. i looked at jenvy, ect.. but at ~140 quid per body it started getting a bit pricey, so i designed my own. i'll use the lost wax method for producing the carbon runners, the rest is machined from solid.

http://i1064.photobucket.com/albums/u36 ... exwecf.jpg

drawn up roughly, may need slight adjustment depending on the relative positions of the two inlet faces on the heads.


because of sump fitment around the e46 front subframe i'll be getting rid of the wet sump and original oil pump and replacing with a 5 stage scavenge pump of my own design, 3 scavenge stages and 2 pressure stages (mainly because im concerned about the extra flow requirements of adding 2 more cams and extra squirted oil cooling) driven from the aux belt in what would have been the aircon position. its on my work computer so i'll get some pictures later.



one thing that i'm interested in at the moment is the fact that bmw added piston oil squirters to the m73 engine (m70 successor) i'm going to see how i can incorporate something similar into the m70 block. i've got a few ideas in my head to play with.



thats it so far. i've been researching and collecting parts for about a year so far, until i understood enough about the various bits to put a solid plan together. i think build time should be about another 18 months.
Last edited by g73a on 16 Jul 2017, 14:50, edited 1 time in total.
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Re: quad cam m70

Postby FAB_BMW » 11 Jul 2016, 06:28

Fantastic, looking forward to seeing progress. What kind of power figures are you hoping for?
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Re: quad cam m70

Postby M60NJP » 11 Jul 2016, 06:41

Given the change in coolant flow, will the 'standard' pump still be used?
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Re: quad cam m70

Postby Gus247 » 11 Jul 2016, 06:45

awesome... I've got absolute admiration for anyone with this level of skill...

Really looking forward to seeing the progress on this one! :)
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Re: quad cam m70

Postby g73a » 11 Jul 2016, 06:55

Not sure about power output, take 2 well fettled 2.5l n/a m50's, double it and minus a bit.

I'm not really that arsed about power, I mainly just want it to sound like this;

http://youtu.be/P1KmxJ6Daic

The mechanical water pump has been deleted to make space for a double chain run up the front of bank 2, there will simply be a hose going into the centre of the v, which will lead to an electric water pump mounted remotely.




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Re: quad cam m70

Postby Discostew38 » 11 Jul 2016, 07:38

Nice little challenge you've set your self
From the engineering side of things anything is possible
The n/s bank heads is going to be a bigger challenge but my guess is your way ahead of me on that and you've already though about it and probably already have plans in your head
It'll be nice to see the finished product and if you can get it in an E46 even better
although I'd like to see it in an E34 (it's a better car) and it would highlight the conversion more

If my memory serves me right
The V6 engine used in the metro 6R4 was actually a rover V8 cut down and literally welded back together
So like I said when it comes to engineering anything is possible

Keep us updated :thumbup:
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Re: quad cam m70

Postby g73a » 11 Jul 2016, 08:37

Just out of interest, does the e34 have adjustable rear gearbox mounts? Like a rail type arrangement that clamps up, or a have I just made that up in my head.


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Re: quad cam m70

Postby Discostew38 » 11 Jul 2016, 11:22

g73a wrote:Just out of interest, does the e34 have adjustable rear gearbox mounts? Like a rail type arrangement that clamps up, or a have I just made that up in my head.


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Can't remember off the top of my head I think it has two mounting positions manual and auto 4 or 6 cylinder mount in different places

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Re: quad cam m70

Postby mt200ish » 12 Jul 2016, 21:41

Very nice will be looking at your progress I heard about this but thought it was an urban myth
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Re: quad cam m70

Postby g73a » 12 Jul 2016, 21:48

I've been to the post office tonight and collected another m50 head, cams and all the related chains sprockets and tensioner bits. Enough to keep me going for now anyway.

If anyone has an 84mm m54 piston they don't want I would gladly take it off your hands!




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