Personally I wouldnt use any other shell than whats meant for the crank to run in. But then again I wouldnt f**k about with an M20
Another 2.8 build.
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DanThe
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M20 and M50 shells carry the same part number on lots of spurious bearing shells, found this out while trying to order shells for my 2.8 crank from the US. The cranks are both cast as is the M52.
Personally I wouldnt use any other shell than whats meant for the crank to run in. But then again I wouldnt f**k about with an M20
Personally I wouldnt use any other shell than whats meant for the crank to run in. But then again I wouldnt f**k about with an M20
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Phatz
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Right folks, just a quick update and some piccies from my build. Haven't been able to progress much on this through lack of time and a few other excuses... 
Anyway, I have spoken to a local engineer about machining a spacer for me so that should be happening any day now. My M20 B20 conrods arrived last Saturday so after giving them a quick clean, I was able to do some test fitting last night. I have however run into a slight issue with the fitment, which I will mention in a minute. 
New rods all cleaned up and looking nice.
Thought I'd try and highlight the 5mm difference between 2.0 and 2.5 conrods with this pic.
M52 crank sitting in place. Moves around well but the webs look quite big to me.... Oh oh...
Sure enough, with rods and pistons fitted, the webs foul the bottom of the piston skirt at this point.
The only plus is that the pistons come to the top of the block just about perfect.
I had originally assumed that because I have the later short skirt type pistons that I wouldn't run into this issue, but it seems I must have a later type crank or something because the webs are bigger. Anyway, I am faced with the choice of either trying to source an earlier crank and trying to exhange it for my current one, or looking at having the excess machined off the pistons.
Just wondered what you guys thought I should do? I reckon I'll be hard pressed to find another crank, although if one did come up I would take it because its a much simpler solution. If I was to go the piston shortening route, what is the best way togo about calculating how much to machine off? Is this even possible on later pistons as the skirt is already quite short, although by rough estimation I reckon its a matter of mm that needs to be removed.
Anyway, I have spoken to a local engineer about machining a spacer for me so that should be happening any day now. My M20 B20 conrods arrived last Saturday so after giving them a quick clean, I was able to do some test fitting last night. I have however run into a slight issue with the fitment, which I will mention in a minute. New rods all cleaned up and looking nice.
Thought I'd try and highlight the 5mm difference between 2.0 and 2.5 conrods with this pic.
M52 crank sitting in place. Moves around well but the webs look quite big to me.... Oh oh...
Sure enough, with rods and pistons fitted, the webs foul the bottom of the piston skirt at this point.
The only plus is that the pistons come to the top of the block just about perfect.
I had originally assumed that because I have the later short skirt type pistons that I wouldn't run into this issue, but it seems I must have a later type crank or something because the webs are bigger. Anyway, I am faced with the choice of either trying to source an earlier crank and trying to exhange it for my current one, or looking at having the excess machined off the pistons.
Just wondered what you guys thought I should do? I reckon I'll be hard pressed to find another crank, although if one did come up I would take it because its a much simpler solution. If I was to go the piston shortening route, what is the best way togo about calculating how much to machine off? Is this even possible on later pistons as the skirt is already quite short, although by rough estimation I reckon its a matter of mm that needs to be removed.
The Sport - Gone to a new home to be slowly brought back to life
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DanThe
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That is a late type crank
I would get the pistons in the lathe though
Either that or whip the crank out again and have some well worthwhile lightening and balance work done on it
I would get the pistons in the lathe though
Either that or whip the crank out again and have some well worthwhile lightening and balance work done on it
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Phatz
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Yeah definately gonna get that done along with balancing the rods, pistons and flywheel. Would a lightening job on the crank involve lossing a lot of metal on the webs and hence sorting the clearance issues? Or would I still have to get the pistons decked?
The Sport - Gone to a new home to be slowly brought back to life
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JazzMan
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Looking good, sorry to hear your having trouble with the crank. I'm sure I saw a post on E30 Tech where the person had machined down the piston skirts - only needed a tiny amount
What are you planning on doing for the engine management?
One other thing I've been thinking about, I wonder if the stock injectors will flow enough for a 2.8 - several threads have suggested that the injectors are close to max flow on a standard engine. Seems to be a bit of a controversial subject though.
What are you planning on doing for the engine management?
One other thing I've been thinking about, I wonder if the stock injectors will flow enough for a 2.8 - several threads have suggested that the injectors are close to max flow on a standard engine. Seems to be a bit of a controversial subject though.
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march109
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I looked into the injector issue, and read on this very site that stock injectors are fine, they are no where near maxed out on the 2.5, something to do with duty cycles.JazzMan wrote:Looking good, sorry to hear your having trouble with the crank. I'm sure I saw a post on E30 Tech where the person had machined down the piston skirts - only needed a tiny amount
What are you planning on doing for the engine management?
One other thing I've been thinking about, I wonder if the stock injectors will flow enough for a 2.8 - several threads have suggested that the injectors are close to max flow on a standard engine. Seems to be a bit of a controversial subject though.
325i Tech 1 Touring, breaking.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
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DanThe
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Well if you want some 2.8 injectors they are £84ish + vat from dealers! 
BTW, did I mention my hoard of 2.8 injectors?
BTW, did I mention my hoard of 2.8 injectors?
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JazzMan
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M52B28 ones? (I've seen some going for an OK price which is why I ask ;) )DanThe wrote:Well if you want some 2.8 injectors they are £84ish + vat from dealers!
BTW, did I mention my hoard of 2.8 injectors?
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DanThe
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Yes, thats each!
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march109
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Is that EACH??DanThe wrote:Well if you want some 2.8 injectors they are £84ish + vat from dealers!
BTW, did I mention my hoard of 2.8 injectors?
325i Tech 1 Touring, breaking.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
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JazzMan
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M20B25 ones (715) are 64+vat each IIRC
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DanThe
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march109 wrote:Is that EACH??DanThe wrote:Well if you want some 2.8 injectors they are £84ish + vat from dealers!
BTW, did I mention my hoard of 2.8 injectors?
DanThe wrote:Yes, thats each!
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march109
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Slow day today, btw you have snail mail arriving tomorrow.
325i Tech 1 Touring, breaking.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
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Phatz
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With regard to injectors I had thought about using a set of M30 ones, though I hadn't researched into it. And management, I'm actually considering sticking with Motronic.
I reckon machining the pistons a little wouldn't be too much of a big deal, just gotta figure out how to calculate how much to remove....
I reckon machining the pistons a little wouldn't be too much of a big deal, just gotta figure out how to calculate how much to remove....
The Sport - Gone to a new home to be slowly brought back to life
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JazzMan
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I've had a bit of a look at http://users.erols.com/srweiss/tableifc.htmPhatz wrote:With regard to injectors I had thought about using a set of M30 ones, though I hadn't researched into it. And management, I'm actually considering sticking with Motronic.
I reckon machining the pistons a little wouldn't be too much of a big deal, just gotta figure out how to calculate how much to remove....
Looks like the 3.5l BMW 6 injectors flow the same rate as the 2.8l ones - the 3.5l ones have a low impedance which matches the 2.5l (715) ones. The M52 injectors are high impedance which I would guess makes them unsuitable for motronic.
You could try attaching a piston and conrod to the crank out side of the block which gives you a good view / ability to measure it up. Or attach a conrod without a piston then hold up a piston to the rod - you should then able to see how many MM you'd have to take off them or the webs
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JazzMan
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Sorry missed your post, I was planning on sticking with stock - but some post suggest they are near their limits, other don't so I'm not sure what to do. I guess start with stock, see how it runs and swap if required will probably be the best approach.march109 wrote:I looked into the injector issue, and read on this very site that stock injectors are fine, they are no where near maxed out on the 2.5, something to do with duty cycles.