The BMW M20 engine

[KnightEngines]

Sounds good, but the car isn't mine & my wife & 2 kids wouldn't be too happy with me taking off to sweden without them.
Not to mention the number of annoyed customers I'd get - got a fairly significant backlog already, maybe 3 months work backed up & more coming, at last count I had somewhere around 8-10 engines on the go & a few more heads on top of that.

Better plan - if he runs an M20 engine & has $$ to play with.

I'll build him a clone of this one, strap it to an engine dyno to prove the numbers (I use a fellow Adelaidiens SF601) & he can ship it over there.
If the dyno used bothers you then see if you can find an independant speedtalk member over here (there are quite a few) to stand in & watch for any shenanigans.
If it makes 380+hp he'll owe me about $25k Au, if it falls short he'll owe me cost of parts & dyno time.
Given my current workload it'd take me at least 3 months to get it built, probably longer if I'm honest with myself - assuming CatCams can deliver another cam in less than 4 months this time.

[KnightEngines]

PS - using the argument "I can't do it therefore this stupid Aussie sure as hell can't" doesn't hold water with me.

I'm happy enough to prove it, but not at my cost & I'm not handing over an engine for scrutiny without being compensated for the IP inside it.

[Leftcoaster]

PS - a larger valve with the seat sunk a significant amount enables a much nicer chamber & also allows a stable short turn.

mmm, trap for those us who don't know the standard sizes of 42.0 and 36.0mm, mea culpa

Hoofing the intake to 45.5mm would certainly count as "a larger valve"

Were the flows tested at 28" of water?

For anyone interested, on Dec 10 2007 Marquis Rex started a S.T. thread titled "BMW M20 flow testing", in which a very sophisticated AVL Tippleman flow bench was used to favourably compare the M20 to competitors

Remain interested in chamber efficiency and flow differences between M20 heads and the 4cyl 2v M10 and M40 series - - pm is ok

[KnightEngines]

Yep, testing done at 28"

Got any pics of the 4 banger chambers?

I have had them through many years ago, but only for rebuilding & I didn't pay much attention to them.

[Leftcoaster]

Yep, testing done at 28"

Got any pics of the 4 banger chambers?

Thanks for confirming - - not everyone tests at 28"

Afraid the 4cyl heads were some years ago & std work only

ps. check for pm

[KnightEngines]

Had a bit of a read of that 2007 thread which jogged a memory - on a larger bore this head was unstable, it would seem the bore itself forms a significant part of the flow path into the chamber on the short turn side, on a larger bore flow fell significantly & became unstable from .300" lift onwards.
I didnt record the #'s, it was just a 'what if' test.
I found that in my 1st round of testing & sunk the valve more once I realised what was going on - had forgotten about that.
With the larger valve being closer to the bore & the seat sunk enough that the bore wall can almost form the 'top cut' for the valve job on that side stability is excellent.

That thread:

viewtopic.php?f=1&t=8652

[Hairyscreech]

Just noticed it was an AMC head, they seem fairly good quality but the standard ports are shocking.
A friend had one on the shop bench recently and we were saying there is a bit more meat in the areas that count, explains the lack of welding and the height of the ports a bit.
I think a stock bmw 885 may struggle to get that height but if this much work is going into a head then a new casting for £600 is hardly bank braking.

[Erland Cox]

It is only that the math doesn't work out and that the chokes on the carbs are as small as your CSA which makes hard if not it impossible to make 120% VE.
If you had used Weber 50:s I would not have an argument.
If everything works out perfect this is what you could have and I admit that it is near:


174.481 Cubic Inches @ 8000 RPM with 114.00 % Volumetric Efficiency PerCent

Required Intake Flow between 205.0 CFM to 217.1 CFM at 28 Inches
Required Exhaust Flow between 155.8 CFM to 168.8 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 360.7 368.3 373.0 377.7
Peak Torque Lbs-Ft 257.0 263.8 266.7 270.6

This is what Pipemax says about my Volvo engine, it made exactly 211.7hp.
I have to admit that I can't remember the exact flow with the carb but peak head flow is 205
and just as your head it levels out from 8mm:


142.355 Cubic Inches @ 6500 RPM with 109.55 % Volumetric Efficiency PerCent

Required Intake Flow between 191.4 CFM to 202.7 CFM at 28 Inches
Required Exhaust Flow between 150.3 CFM to 162.8 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 204.7 209.0 211.7 214.4
Peak Torque Lbs-Ft 182.4 187.2 189.2 192.0

All dynos and flow benches differ but you have undoubtedly made me interested i playing with some of my BMW:s.
I have a bunch of E28:s but most of them are with M30 engines.
I have lots of parts and also junk heads for M20:s to play with though.
A double M20 like a V 12 would be interesting but I don't know if there are any cams for them.

Erland

[morerevsm3]

my son has an M10 head in his shed at Heathfield if you want to look at one Tony

[KnightEngines]

I wonder if we could graft 2 of them onto something like a rover V8, use beamer slugs etc.
That'd be fun.

If he's going past here at any time & the head is surplus to requriements by all means get him to drop it in.

I think Geach wants me to fiddle with an M10 for his 2002 at some point, but he still wants to drive it on the road.

Can you ask Rob if the chokes were 40mm or 42mm? - brain fart, maybe they were 42mm.
I remember he was concerned about tuning them with the choke sizes I wanted, but it was too long ago - I struggle to remember what I had for breakfast.

Erland - could well be the carbs have 42mm chokes, 2.15^" CSA.

[KnightEngines]

Just noticed it was an AMC head, they seem fairly good quality but the standard ports are shocking.
A friend had one on the shop bench recently and we were saying there is a bit more meat in the areas that count, explains the lack of welding and the height of the ports a bit.
I think a stock bmw 885 may struggle to get that height but if this much work is going into a head then a new casting for £600 is hardly bank braking

Yep, stock the AMC ports are a bit poo, well behind the stock BMW ports.
But it doesn't matter much at all when you're grinding the crap out of it anyway, all that matters is the material quality & how much of it there is where it's needed!

[morerevsm3]

they are machined to 42mm
there has been several E30 325i's on his dyno, stock they make ~95RWKW for a healthy one, up to ~105rwkw with some AFM tuning and long tube headers

[KnightEngines]

Cool, coz Erland is right, 40mm chokes would struggle.
I reckon I talked through that with Rob & we settled on 42mm being the largest he had any hope of tuning - for some reason I thought it was 40mm coz he had 38mm chokes in it before.

I wonder if a set of 48's with 44mm chokes would see any gain.

[morerevsm3]

re the M10 head, he is going to turbo his M10 E30 and run in IP while he saves some money to build his M44 for proper fasts

[Erland Cox]

We had a dyno competition where we brought our own heads for an old Volvo push rod 4 cylinder.
Everyone used the same camshaft header and intake, the carbs were unmodified Weber 45:s with 38 chokes.
The best heads with that combo were up at 195hp and later the engine was tested with Weber DCO 50mm carbs with 46 chokes.
When the head used was flow tested with the 38mm chokes the flow at 12mm was lowered with 13,8%.
The stock DCO 50 with 46 choke only lowered the flow with 7.6%.
Instead of 195 hp the engine now gave 214hp, 19 hp more.
It should be interesting if you tested with 50DCO:s, all DCO:s have the same internal dimensions from 48:s to 55:s.
On my own Volvo I also tested different velocity stacks and ones that tapered from 48 to 52mm before the radius in the end were up 4hp on my 4 cylinder.
I used stacks that don't go into the carb and butt up against the booster like the ones used on Weber DCOE 48:s.

Erland