M20 B20 Options (Again!!)

[johnt0709]

Have an M20 B20 engine (injectors bit noisy 140,000miles)

What are the best options.

1. Carry out work on existing engine retaining existing engine number which appeals to me ( What work and how much)

2. Drop in a B25 engine - worried about condition.

3. Source a B25 and get work carried out to it (what work and how much?

Project for Autumn/Winter 2010 - just planning ahead as some of these projects seem to involve a long 'lead in time' sourcing parts.

Any other thoughts (sensible)

[jbh]

realy depends on what you want. only you can answer it. with the b25 youll get more grunt and better tourqe. i personaly would go with the b25 but thats just me as i fell there a beter engine. I know of a few good b25 engines but then it could be worth buying a 325i breaker. get your engine and other odds and ends you may need and get some cash back into the bargain.

what needs done to your b20? the mileage isint moon miles

[johnt0709]

The B20 engine is OK if not just a bit ticky with the injectors - just looking for a bit more under the bonnet - the car was restored during the winter months - doings springs and brakes just now and looking at engine options after summer 2010?

Just dont know if Im better to get a B25 rebuilt, buy one already done, or carry out work to the B20 rebore etc?

[jbh]

The B20 engine is OK if not just a bit ticky with the injectors - just looking for a bit more under the bonnet - the car was restored during the winter months - doings springs and brakes just now and looking at engine options after summer 2010?

Just dont know if Im better to get a B25 rebuilt, buy one already done, or carry out work to the B20 rebore etc?

you could buy a known good one that you can hear running or buy a cheap one and rebuild it but this could run expensive it really depends on what your budget is

[wullie325i]

for a fresh engine start with a b20 and bore it out and fit b25 running gear in it you will then have a new engine if you do the b25 head aswell.

if it was me i would buy a running 325i compression test it before you buy and if its good just freshen everything else up and a service and you will have a good b25 engine and you can rob the donor car for the bigger 51mm struts and rear disk conversion aswell then frag whats left to get some sheckles back.

simples!

[johnt0709]

Wullie - option1 bore out, fit B25 head - what would the cost of this be (roughly) plus ECU and diff change - anything else needed?

I know that the 325 option is what you pay for it- plus any associated costs with the swap, plus running gear?

Car has rear disks on it just now? In the process of renewing them, have bought new springs and about to sort out brakes after santa. (kids first i suppose )

[Speedtouch]

If I had an M20B20-engined car in good original condition, I'd be looking to slip in a 323i crank - the standard 320i bore is retained, but the extra 10mm stroke gives up to 150bhp, so is a very insurance-friendly stealth mod!

[johnt0709]

Guess Im looking for best option - cheapest for more bhp

[ImysE30]

2.7 ETA?

Gareth has the bottom end you need for sale.

I would stick a b25, around 40 extra BHP for not a lot of money.

I've got a b20, i could spend money on it to make it go quicker but i think it would be better to start with a more powerful engine, then go from there, that's my personal opinion.

[johnt0709]

Thanks looks more and more like trying to pick up a decent b25. I knew other guys would have had the same dilemma

[wullie325i]

Guess Im looking for best option - cheapest for more bhp

shop around for a decent m20b25 jbh breaks cars quite regular and im sure if he had one you could go over and hear it running.

diff will be cheap as unless you want a slipper everything else you have i think so just engine loom ecu.

you could retain the 320i diff + gearbox and it will yeild good acceleration due to the ratio and save a few £££ although they are thought to be weaker but i know of a few cars running them with no issues.

m20b25 engine in good order is the cheapest plug and play option for more bhp.

mind you i could do you a deal on a m50/2 conversion if you wish

[jbh]

Guess Im looking for best option - cheapest for more bhp

jbh breaks cars quite regular and im sure if he had one you could go over and hear it running.

diff will be cheap as unless you want a slipper everything else you have i think so just engine loom ecu.

you know me to well Wullie.. if I pick one up with a good engine I can let you know. weve currently got 2 realy good b25's in but both are spoken for sadly. if I pick up a 325i your welcome to have first refusal if thats the route your wanting to go. id throw in the g/box . prop and diff.

with your car being the cab it will already have the 51mm front struts so I wouldnt worry about that

[wullie325i]

forgot about the struts on the cab 51mm right enough doh

[jbh]

forgot about the struts on the cab 51mm right enough doh

not to worry Wullie.. the cab was pretty well speced in the suspension wise. even the 4 pots had the 325i brakes and 51mm front the tourers were the same

[StuBeeDoo]

If I had an M20B20-engined car in good original condition, I'd be looking to slip in a 323i crank - the standard 320i bore is retained, but the extra 10mm stroke gives up to 150bhp, so is a very insurance-friendly stealth mod!

That's what I was going to do.
You try finding decent M20B23 pistons, though.

I ended-up going 2.7. That's stealthy to the unknowing eye too.

[jbh]

if your wanting to go down the 2.7 road send me a pm I can lay my hands on another eta bottom end

[johnt0709]

pm'd.

Not bothered about wait - work is plannned Oct/Nov 2010

[johnt0709]

Just did a bit of reading on this and starting to sway towards the ETA bottom end and b20 head - what else would need changed or recommended changing/renewing before building back up?

[wullie325i]

exhaust - diff - gearbox for 325i items - not essential put will be better if you do.

using the 320i head will limit the gains you will get over the b25 head but in essence you can just slap the b20 head on the block and away you go.

why 2.7 over say a m50?

[goosiegander]

My 2.0 was bored out to 84mm and with the aid of crank/cam/pistons its now a healthy 2.8 circa 200bhp.

Bang for buck

[jbh]

why 2.7 over say a m50?

couse it looks right under the bonnet

[wullie325i]

m20b28 at 200bhp which is damn good far an m20

or

m52b28 at 194bhp standard and it's a lighter engine too with pretty easy potential for around 240bhp without going mental.

m50b25 also 194bhp with a bit less tourqe.

m20b27 with 320i head the bhp varies alot between builds as does the b25 head route.

[wullie325i]

why 2.7 over say a m50?

couse it looks right under the bonnet

who cares james i would have no problems putting a wankel engine in an e30 if the gains were to be had.

maybe twin rotary hmm u have me thinking now

[StuBeeDoo]

why 2.7 over say a m50?

couse it looks right under the bonnet

Damn right James.
Also it's plug and play. Not everyone can be bothered fabricating exhausts, sourcing different e28 and e34 parts.

[wullie325i]

why 2.7 over say a m50?

couse it looks right under the bonnet

Damn right James.
Also it's plug and play. Not everyone can be bothered fabricating exhausts, sourcing different e28 and e34 parts.

bah bloddy purists.

get the tool box and the welder out and have at it you swines.

[jbh]

bah bloddy purists.

I wouldnt say purists as lets be honest.. mines isint going to be a factory fresh tech1 sport.. theres more than likely going to be a few eyebrows raised when my hartge themed tech1 hits the road..

[johnt0709]

Sorry wullie - im a bit anal and would probably fall into the purist bracket as well. What would be the norm using the eta bottom end bearings, shells or would they normally just be checked. Also read that the b20 head works better?

Got me it's important that it looks right under the bonnet.

[jbh]

im planning on using the b25 head on mine as it doesnt need any work. if you read the wiki article it does say that they gained a good result from putting the b25 head on.

taken from the zone wiki
"Use the standard Eta bottom end with a 325i head, the 885 unit. The 325i has strange pistons with a deep dish but a raised section at the front of the combustion chamber to accommodate it. Despite what experts say, the 325i head will NOT give a horribly low compression ratio. The difference in chamber volume is quite small. The 325i head has a chamber volume of @ 42.5cc and the 731 and 200 heads have a chamber volume of @38cc. It all depends on whether the head has been skimmed. But 4.5cc difference isn't much at all and much of the increased size of the 325i chamber is made up for by the bigger valves and surrounding raised areas around them. 325i valve sizes are 42mm inlet and 36mm exhaust.
A lot has been said about Eta pistons being incompatible with the 325i head. Most of it is nonsense as this has been done many times and it works okay. Of course it won't give results quite as good as using the matching 325i pistons but it still has a good compression ratio which is most of the battle won.

Again, depending on which gasket is used and whether the head has been skimmed, using a 325i head on a later 10.2:1 Eta short engine will give a CR of 9.4:1 which is plenty. If you can even find an early 11:1 Eta engine, the CR would be 10:1 which is even better. Because you are using a 325i head, just bolt a 325i inlet manifold straight on.

I converted a 1986 525e Auto to this spec and it was very lively - 0-80 in 21 seconds which is just 1 second slower than an auto 528i which has both 184 bhp and a lower final drive. Then I pulled the engine out and it went into an E30 Touring "

[stonesie]

Stroke it

My 2.8 is also around 200bhp (206) and I could have built it cheaper, but I got carried away with replacing things "while I'm at it"

The clutch is a 325 LUK one and the gearbox/prop are standard 320, the 3.73 325 diff cost £35 and the exhaust is standard 325 including the log manifold with a new centre box and Magnex back box for a bit of growl, but I would seriously recommend re-bushing the back end, my car had only covered 123K and it made a massive difference.


If you put your head on a ETA bottom end it will give good torque, if you go for a 325 head then you are best off using the matching 325 pistons as these heads rely on the different shape and squish to do what they do.

[johnt0709]

Yip - Im a bit of while im at type as well - thats what I'm afraid of.

Im 90% decided that Im going to go with the eta bottom and b20 head - 2.7 is plenty - drawing the line firmly there.

[daimlerman]

Reads like the OP wants to keep a standard looking engine bay,so the way to more power is via increasing capacity.
Three options...
1.Fit a stock 325i engine
2.Build a 2.7
3.Build a 2.8
You can retain your original block/engine number with options 2 and 3,at the cost of having it bored out to 84mm,expect to pay about £30 per bore,£180ish for the block.
Then it depends on crank availability,decent,unworn eta cranks are starting to become like rocking horse whatsit,so an M52 (2. crank with your 320 rods and 325 pistons/head could be the easier option,digging out Stonesie's and Goosygander's build threads will give you a good idea of the work involved,both have built first class strokers.

[Gunni]

I would wote for the 2.8 everytime as it doesn´t require a vernier pulley to keep cam timing right.
A uprated cam will wake it up real nice.

[wullie325i]

the 2.8 m20 is a better choice in my opinion if you want a stock looking m20 as it will give the best gains.

i have m52b28 cranks quite often if required and could also do the conversion if needed.

[AlpineAde]

The 2.8 is the new 2.7.

I wouldn't even consider a 2.7 now.

[wullie325i]

The 2.8 is the new 2.7.

I wouldn't even consider a 2.7 now.

2.7 still has a place but the best gains from an m20 will be the 2.8.

theres no replacement for displacement lol