m20b25 consultation..

[Brdjo]

Recently I stumbled on a m20b25 engine for some low price with ECU, injectors, but without AFM.. Engine has blown head gasket or cracked head, owner sad that when started up it spils oil somewhere niar head gasket and mess up engine bay. Also after some time it starts to overheat...
Engine is now in 1993 e32, and far as i know e32 never came with the m20, so it must be some kind of swap..

I am interested in your opinion about this one, because i have m20b20 in my car who is quite worn out and definitely must do something about it.. Regulation in my country are strict so my block must stay, so I was thinking bore my block, and use b25 internals, and you can see where this is going..

If I had luck the head will be ok (very low chances that she is ok) but I am concerned about overheating and what that can do to bottom end.. Also any suggestion on what to pay attention while I am there.. And should i go for it?

[Brdjo]

Any suggestions? Did anyone bored b20 to b25, how rebore block is going to work, any known issues?

[Brianmoooore]

It's reputed to be possible in most cases. A few B20 blocks will have a defect in the casting that results in them becoming porous when bored to B25 diameter, but you won't know if yours is one until the work is done.
IIRC, there's a few steam holes missing in the deck of the B20 block when compared to the B25, but this doesn't cause problems in practice.

[maxfield]

It's reputed to be possible in most cases. A few B20 blocks will have a defect in the casting that results in them becoming porous when bored to B25 diameter, but you won't know if yours is one until the work is done.
IIRC, there's a few steam holes missing in the deck of the B20 block when compared to the B25, but this doesn't cause problems in practice.

People in the past have used B20 blocks bored to B25 in turbo setups as the B20 strong is stronger due to mess steam holes.

[Brdjo]

Thanks Brianmoooore and maxfield, I didn't know that.. So basically when boring b20 to b25 you hope that everything will be ok..?

I think i will buy this m20b25 because the price is like 60euros for complete engine without AFM, and hope that bottom end is ok..

[steve_k]

IIRC ant at atech used to bore a B20 block to about 84mm when he was building a b27, as jamie above says due to the b20 block having less steam holes & therefore theoretically being the stronger of the two.

[Brdjo]

Thanks, idea is to build stock m20b25 with my b20 block.. the car is daily drive so I am trying to keep it simple as can be
The day after tomorrow I will go to see engine and will keep you posted..

Please let me know if you have any suggestions, but when engine comes home and disabled we will know more

[Brdjo]

I bought the engine.. It;s not in good condition, but at least I got ECU, injectors, crank, alternator, starter and power steering pump for 50 euros xD

Engine did not mix water and oil, did not bend valves, even when starts up runs smooth no hesitation or strange noise.. only oil leak from 6 cylinder on exhaust side, and as seller said it is overheating (did not keep it running to rise temp).

I disassembled the head (885) to take some measurements and see little more and the fun begins xD

First I found that 5 and 6 piston are somehow hitting the head, not valves, head.

Pistons 5 and 6
https://ibb.co/hdGtD5
https://ibb.co/fxB4Lk
Head
https://ibb.co/nQjKmQ
https://ibb.co/mS5aRQ

So that will explain oil leak from cylinder 6, gasket get lose and oil comes out.. i guess so.

Then the are those crapy coolant holes..
https://ibb.co/fztvRQ

And in the end deck height, I read somewhere that factory height is 125,1mm is this true? My has 124,35mm..
I am not an expert on subject, and seeing that pistons I have to ask, is this ok height and can it be usable again if flatten out?

I was measuring hire: https://ibb.co/cbZVt5

Some pictures of head marks, I believe.
https://ibb.co/iJtjLk
https://ibb.co/fztvRQ
https://ibb.co/juDJfk

So if it can be usable again i will send the head to mashing and testing if not, make a garage table xD

[Brianmoooore]

That looks like a freshly (and excessively) skimmed head to me! That would explain the lack of deck height and the piston contact, and coupled with less than expert assembly/poor quality gasket, also the oil leak.
Contact can be sorted by using a thicker head gasket or grinding out the combustion chamber where the contact is occurring.
No comment on the pistons without seeing them in the flesh, and the corroded coolant passage* is near the limit, to say the least. You need to lay a new head gasket on to see how much the corrosion undercuts the fire rings to check.

*This is what happens when antifreeze isn't kept up to strength, or changed often enough!

[Brdjo]

Totally agree that someone without experience is eseblemd this one...
ohh I forgot to post what i find in the head a screwdriver..

https://ibb.co/kgcQt5
https://ibb.co/hypumQ
https://ibb.co/g6CfRQ

Brianmoooore I think that machining job is not done right, head on 5-6 cylinder i skimmed more than on 1-2 (if those little rings on sides indicate a head thickness)... I don't know how is that possible, but guessing who can manage to left screwdriver in the head can also screw the flattening out..

So should i try to repair the damage, and make it work again? is anyone had so flatout head and what gasket should i use, thickness?

And I will definitely need some numbers about gasket thickness, piston pop out from b20 block with b25 piston, crank and connecting rods.. any help is very much appreciated

[Brianmoooore]

I had something similar to this on a 325 E30 many years ago. It had cracked its head (airlock after coolant change) and a replacement head was obtained from a "professional" reconditioning company.
Was fine when the engine was first started, but as the engine warmed up, a distinct tapping sound could be heard, getting louder with engine temperature.
Subsequent inspection found that this head had been skimmed beyond its intended limits, and was sorted by supplier grinding out the combustion chambers. Worked fine for 100,000+ miles after that.
BMW can supply a gasket that is 0.3mm thicker than standard.
The best thing you can do is take the head and block to a member of the equivalent in your country of the UK "Federation of Engine Remanufacturers", if there is one, and ask the opinion of someone there with many years of experience as to whether this is salvageable or not.
If, and when it's sorted, the head should be test fitted onto the bottom end, using and old, compressed gasket and old bolts half tightened down, with little lumps of Plasticine stuck around the tops of the pistons.
The engine should then be turned over twice by hand, and head removed again, and the thickness of the flattened Plasticine measured.

[Brdjo]

Thanks for your help, I will disassemble the head and take it to shop, and then we will see what they have to say.. I was gonna throw away old gasket, but will keep it for test purposes...
I was thinking to do some welding around coolant passages, before skimming down head. Thinking about this: http://i46.photobucket.com/albums/f134/ ... adfill.jpg
Read that this is good for HG and preventing HG fail, any experience with this?

Today friend looked over the head and he has opinion that rough head walls are not from piston contact, basically he thinks that age and poor maitenes lead to this, and the head after refurbishing will be good to go..

[Brianmoooore]

It should be possible to build up around the inside of the crescent coolant hole with weld, but then the head will need skimming again, and if it's already skimmed past the limit.....

[Brdjo]

I was thinking first to do welding and than skimming..

[Brdjo]

The head is sent to shop.. After the head is machined I will try fit test and see is head still usable...

[Brdjo]

Head is still in the shop...

Can someone tell me how to identify what crankshaft bearing should i use? white, green or yellow? What is the difference?

[Brdjo]

anyone?

[Speedtouch]

I would imagine the difference is in the sizing, e.g., for +0.010", +0.020", +0.030" (thousands of an inch) regrinds of the crankshaft - if the crank journals have to be ground due to ovality/wear, you need to fit the matching bearing, so if for instance, 0.010" is ground from the crank journal, you would need to fit a +0.010" oversized bearing to take up any excess play.

[Brdjo]

No, difference is not in sizing far as i can tell.. This is what i get from realoem.. so yellow, green, white is in every size. If i have to guess i'll tell that is different build material or something like that.? But i will need someone who know for fact what is going on..

Bearing shell yellow 60,00MM(0) 6 03/1988
Bearing shell green 60,00MM(0) 6 03/1988
Bearing shell white 60,00MM(0) 6 03/1988
Bearing shell yellow 59,75MM(+0,25) 6 03/1988
Bearing shell green 59,75MM(+0,25) 6 03/1988
Bearing shell yellow 59,50MM(+0,50) 6 03/1988
Bearing shell green 59,50MM(+0,50) 6 03/1988
Bearing shell white 59,50MM(+0,50) 6 03/1988

[Speedtouch]

Can't you see what colour the originals are, and just go for some matching ones?

[Brdjo]

I was looking for color on them.. even on crank but could not found.. eny idea where to look?

[Speedtouch]

No, however, most bearing shells are stamped STD (standard size) or in increments of size, e.g., 0.020, etc.

[Brdjo]

Stamps are ok, they can be seen, but I am curious what is color for, and what color defines..

[Quaser]

if you need a thicker head gasket, you can use an mls gasket from cometic - people who turbo their cars use this to lower compression and its available 0.03, 0.04, .... up to 0.140 inch!!

[Brdjo]

if you need a thicker head gasket, you can use an mls gasket from cometic - people who turbo their cars use this to lower compression and its available 0.03, 0.04, .... up to 0.140 inch!!

Thanks, good to know.

I think i find what is color think, but i think this is not the case in m20 engine.. because m20 have 3 colors and all 3 colors have 3 same dimensions..
http://forum.e46fanatics.com/attachment ... 1334082999

[Brdjo]

Head job is done. Valve are sealing excellent, no cracks in water and oil channels.. also added welds on cooling passage..

And the engine is sold..

I makeup my mind to not go with swap and make b25 out of my b20.. It will cost like the same as rebuilding my b20 and will make car illegal, so i decided to rebuild my b20 when time comes and keep it in factory spec...

as always thanks everyone for help..