M20 build / re-build / replace or other conversion???

Post Mon Dec 02, 2019 6:43 pm

Right, got to do some serious thinking now and might need some help making a decision!!!

My M20 2.7 is now pretty much dead - (Compressions test: Cyl 1 - 0, Cyl 2 - 105, Cyl 3 - 87, Cyl 4 - 89, Cyl 5 - 72, Cyl 6 - 103).
As pretty much nothing about/in this engine is standard, I'm worried that a rebuild is going to be very time consuming and expensive. Plus I'm not really sure I've ever been 100% happy with this engine and spent a crazy amount of money having it built the first time around.
I know it's almost impossible, but can anyone give a rough idea of cost on this route (including labour)???

I'm assuming the cheapest route by far, would be to put in a standard M20B25 - though I have done this before and not been that lucky!
What sort of money does a standard lump in decent condition normally go for nowadays???

The other option, (in my head at least), is another conversion to a different engine. I'm thinking V8, as I've always wanted one in an E30.
I'm also assuming this will be by far the most expensive! Again, any ideas on the conversion/labour costs if I took a running car in as a donor???

Open to other suggestions?????? (not the petrol & matches kind!!!!!)
Other slightly more modern engines, that could be cost effective???

Writing this, I can guess I'm probably going to end up with a standard 325i engine going in, which to be honest, I find disappointing.
Spent so much on this car in the last month, this is horrific timing!!!

Post Wed Dec 04, 2019 11:14 am

Surprised to not get any opinions on which way to go with this!!!

Maybe in the wrong section, but is any engine conversion particularly easier/cheaper than the others, If I were to pick up a donor car over the winter???

Post Wed Dec 04, 2019 12:36 pm

I'd buy Clarko's M20B25 - at that price you're up and running in no time for a very low price - assuming the unit is OK - you pay that much for an 885 head!!

You could then look at the B27 internals and see what needs doing and spread the cost over a year or two??

Paul

Post Wed Dec 04, 2019 1:02 pm

Bugger - didn't see that and he put it as sold yesterday!!!

Post Thu Dec 05, 2019 2:36 am

what was done with respect to the 2.7 build? you could just fix that flaws when you rectify whatever issues you have now. did you do any further diagnosis to work out the 0 compression issue?

Post Thu Dec 05, 2019 2:26 pm

What was done was... pretty much everything!
Was originally done for me by Ant at Atech...
Was a bored out 2.0 block, decked, custom pistons, head skimmed and flowed, cat cam, bbtb, maf conversion - I'm sure there's more I've missed!!!
No expense was spared - spent an absolute fortune and tbh never been satisfied with it, always little niggles/issues - so the last thing I want to do is spend that money again on a full rebuild to be a bit disappointed!

Further diagnosis such as????

The garage I've used for this car for some time, pretty much said the only option for this engine is out & apart - which is time and money before you find out what is really wrong!!!
They could guess at scraper rings - but it's a guess!!!

Getting sick of pumping money into a lump that never quite runs right, so looking for alternative options at the mo!!

Post Thu Dec 05, 2019 2:40 pm

I have been having this 'which engine' dilemma for years now, to the extent that I had sourced most of the parts to make a nice 2.8 M20. However, a decent M20B28 will cost a lot to build and if anything goes wrong with it would likely cost a lot to fix too, as you mention above. That got me thinking about other options, I did think about a V8, but it is a lot of work, then I started thinking about an M54. This appealed to me as I already have an E46 330i as my daily so knew t he engine well. Apart from the slightly suspect cooling system (which I wouldn't be using in my E30 anyway) they are pretty bulletproof and an M54B30 in standard form it makes more power than nearly all M20s.

I managed to get donor E46 for next to nothing and although I wouldn't say it has been a cheap engine swap it hasn't cost the earth. Due to it being a bog standard M54 if it does decide to explode a replacement M54 engine can be had for £500 or thereabouts and there are plenty of them around too. Another bonus is that as my daily is an 330i if either goes wrong I can swap bits into it from the other to fault find or fix it.

Yeah, I took a deposit on my M20 engine a few days ago, it is due to be collected at the weekend.

Post Thu Dec 05, 2019 3:57 pm

Interesting idea - will have a read of the M54 section of the forum tonight.

Will potentially need a more sensible car over/after Christmas, so option is there to buy & fully test a donor!

Post Thu Dec 05, 2019 4:06 pm

There's not much in the M54 section tbh, I have been meaning to do an update to my build thread about my swap but haven't got round to it yet, that and I haven't finished the swap yet.

There's plenty of information on US sites about M54 swaps, this is one of better ones I found:

https://www.r3vlimited.com/board/forum/ ... swap-guide

I'm not sure why it isn't a more popular swap over here as there are plenty of E46 330i's around for donors.

Post Fri Dec 06, 2019 12:59 am

Thanks mate, I'll have a browse when I get a chance!

Post Fri Dec 06, 2019 11:56 am

Also - I've got a 2001 325ti (E46 Compact), with the M54 2.5....... that gets through a bit of engine oil!!!
The garage I use has said it's probably the ccv/breather assembly that's the main cause - I'm sure they told me ages ago that BMW used to recommend replacing the breather assembly every 2nd/3rd service or something (I think) and it's quite labour intensive/costly, so usually not done.
Does that sound right? Any idea what intervals???
No problem doing it before the engine goes in, but don't really want to be re-doing that every year!!!

I'm hoping I'll do quite a lot of mileage, if I eventually get this sorted out!

Post Fri Dec 06, 2019 12:19 pm

Yeah I have heard this too, I replaced all ccv pipes etc. when my M54 engine was out, it was quite fiddly even with the engine on a stand so I imagine it would be a bit of nightmare if the engine is in.

I think it depends on where you and how cold it is as to how often this needs doing as the frequency it gets bunged up is down to how much condensation there is in the pipework. I thought it was more of a case of replacing it when required rather than there being a specified frequency for replacement.

Post Fri Dec 06, 2019 12:45 pm

I don't know if it is the same with the M54B25 as the B30 but the design of the oil ring is not good on the M54B30, on top of that it seemed to depend a lot on how they were driven when new.

I'm probably going to end up stripping the M54 down a bit anyway to change the cams so I will probably put new rings on the pistons with M52TU oil rings and maybe re-hone the bores to see if it helps the oil consumption.

Post Fri Dec 06, 2019 6:29 pm

Those m54b30 engines are well known for the high oil consumption. BMW even made a statement stating that 1 litre of oil per 1000 miles was acceptable.....

Post Sat Dec 07, 2019 9:29 am

boiliebasher wrote: ↑
Fri Dec 06, 2019 6:29 pm
Those m54b30 engines are well known for the high oil consumption. BMW even made a statement stating that 1 litre of oil per 1000 miles was acceptable.....

Yes but it doesn't make it right or mean the issue can't be fixed or at least improved. They said something similar about Nikasil

Post Sat Dec 07, 2019 10:52 am

flybynite wrote: ↑
Sat Dec 07, 2019 9:29 am

boiliebasher wrote: ↑
Fri Dec 06, 2019 6:29 pm
Those m54b30 engines are well known for the high oil consumption. BMW even made a statement stating that 1 litre of oil per 1000 miles was acceptable.....
Yes but it doesn't make it right or mean the issue can't be fixed or at least improved. They said something similar about Nikasil

I completely agree. I considered buying a M54b30 engined E39/46 before I bought my 540i and researched the subject quite extensively. I came to the conclusion that if I wanted something that burnt that much oil, I was just better off buying an old diesel instead!!

But in all seriousness, from what I found out the main culprit for the mysterious high oil consumption was usually due to piston oil scraper rings and wrote those engines off because of it.

Post Sat Dec 07, 2019 11:35 am

miniblob wrote: ↑
Thu Dec 05, 2019 2:26 pm
What was done was... pretty much everything!
Was originally done for me by Ant at Atech...
Was a bored out 2.0 block, decked, custom pistons, head skimmed and flowed, cat cam, bbtb, maf conversion - I'm sure there's more I've missed!!!
No expense was spared - spent an absolute fortune and tbh never been satisfied with it, always little niggles/issues - so the last thing I want to do is spend that money again on a full rebuild to be a bit disappointed!

Further diagnosis such as????

The garage I've used for this car for some time, pretty much said the only option for this engine is out & apart - which is time and money before you find out what is really wrong!!!
They could guess at scraper rings - but it's a guess!!!

Getting sick of pumping money into a lump that never quite runs right, so looking for alternative options at the mo!!

diagnosis to work out why the compression numbers are bad. might just need a head job and a few valves. either a leakdown would probab ly help and a camera down the plug hole

what kind of niggles?

Post Sat Dec 07, 2019 1:14 pm

I'm still absolutely shocked that considering this engine was essentially brand new that it's failed so early on.
I personally would say something wasn't quite right when they rebuilt it.
How many miles/ long ago was this m20b27 engine built may I ask?

Post Sat Dec 07, 2019 2:12 pm

I asked about doing a leakdown test and they were confident there was really no point as it will need to come apart either way.
Normally I'd agree with further investigation, but at the end of day that all takes more time and money, before you even know what needs doing and at what further cost!!
I'm running out of budget at he minute, having just spent a decent amount on body/paint and other bits!
This might have to be parked for a few months!

Niggles from constant pressure in the cooling system to intermittent misfires that feel like a gap in the map that just can't be tracked down! Just not convinced it's ever really run 100%.
It's had stuff done over and over - even gave up mapping on the first ecu system Ant recommended and then had a Uni chip fitted and mapped by someone else on here!
It's just constant money - and when I'm using it, I do a lot of miles, so prob not really suited.

I agree though, I expected more and for it to last longer.
I haven't looked through paperwork, but it could've been 6/7, maybe even 10 years since it was built - (third engine I've had in this car!!!).
Sometimes it's sat for months, sometimes I've done 500+ per week in it - I've driven it hard, but kept it serviced.
It's had a few dash clusters too, so no idea on mileage off the top of my head! Last three weeks back on the road, I'd done prob 1500 to 1800miles and it was just running as well as it ever had, (albeit using a bit of oil), then 1 turn of the key and that all changed again!

I was relying on driving this daily for a bit, so just had to spend nearly £600 geting my E46 compact back on the road, so budget is pretty much done until after christmas!

Post Sun Dec 08, 2019 8:09 am

I don’t agree that proper diagnosis costs unnecessary money. It stops you spending unnecessary money as you find out the root cause. It seems more like you’ve made up your mind that aren’t going to fix it.

Logic says there is a fair chance the engines going to come out irrespective of the option you choose so a bit of diagnosis is nothing.

If your concern is a very time consuming and expensive process then a motor swap is probably not what you want IMO. Doing things properly always costs a lot more than what is estimated and you are dropping in an engine with unknown history and even more potential for niggles.

Post Mon Dec 09, 2019 2:41 pm

Sorry mate, may not have come across how I meant!

I agree with finding out the cause, it's not unnecessary at all - as you say, it'll be coming out at some point anyway, so it will get cracked open!
However, I've spent a lot of money trying to find out what's going on with this engine since the start and I'm running out of funds!!!! No decision has been made yet, but do I go again and keep ploughing money into the same engine, that keeps disappointing me, or take a different direction???
I'm happy to spend time and money - been there and done that, several times - but I expect it to be done after that and hopefully reliable from that expense.
Well aware there is potential for niggles, etc, but I wouldn't expect much more than with any second hand car - especially if I ran a donor for a while and did a well known swap!!!

This will probably be parked up for a few months now, while I think it over.

I've had to prioritise what funds I've got left to sorting out & MOTing my E46 compact so I've got a car - and the other halfs car, after she met a nasty pothole on Friday night - tyre, poss wheel & at least tracking!
Just in one of those stages at the mo where I just hate cars again now, but essential for us to have a reliable car each - just bad timing!!!

Post Tue Dec 10, 2019 5:30 am

if you let us know all the niggles and the all the specific details with exactly what was done we can help as it may indeed be a fundamental issue with the bottom end that is a cut your losses situation i.e. if needs new slugs and full rebuild. Custom pistons back then were often pretty ordinary depending exactly what they are and were usually not meant for engines that will see many miles.

i guess best case its just a head issue and tuning / ecu is causing gremlins. The m20 is as simple as chips the pressure in coolant would get rectified with a head rebuild and new HG gaskets. blow away crappy MAF's they dont work properly on M20 unless youre a lucky one. a standalone plug and play system is probably need for this kind of engine with all the bells and whistles.

if pistons are damaged or signs of other wear issues then yeah its probably abandoned ship and swap a known running engine.

i think what you want to know is find out if its a bottom end or head issue or both. Leakdown might help narrow down but head off at some point when youve saved some coin. if youre handy and can do yourself its about an afternoon job or so not much worse than a timing belt.