M20 B20 Head Rebuild

[Bfab]

I wondered if anyone can help

Ive been experiencing extereme lack of power and misfiring and was told that my engine head is damaged and needs rebuilding.

I was advised to either get the whole engine rebuilt or to find a replacement which has done miles.

The engine has 125000 miles.

Was told something about the head will be too strong for the bottom end and could lead to problems.

Is this true or have I wrongly been advised.

[toby]

For the cost of a 325i engine, it would make sense to put that into replace the existing one.

I know someone who has one and can fit it. (pm me for details)

[Bfab]

Ok. But is this a straight forward swap?
I was thinking to put a reconditioned one in if going for the whole engine swap option.

[toby]

It is a very straight forward swap but, as with any cars this age, it's the inevitable extras that appear along the way that increases costs. A lightly reconditioned engine would be a wise idea.

[Bfab]

Is it wise to rebuild just the head? I know someone selling a B20 head. How much does he want for the 325i engine and how many miles has it done

[eta]

Also remeber an engine swap will affect your insurance a head rebuild won't.

[Bfab]

I didnt realise that. Prob best to stick with new head. Will rebuilding head effect bottom end tho

[daimlerman]

Cylinder head is the 'heart' of these engines,bottom end,as long as the oil/filter has been changed regularly,will run and run,250k miles is not unusual for a properly maintained engine.

Does the oil pressure light go out as soon as the engine starts?

If a cylinder head is re-built properly by a professional,expect to pay around £750,if you do as much as possible yourself and just farm out machine work,you can more than half that fiqure.

Or you can take a chance with a s/h engine bought for £100-£250...if you are able to do the work yourself,this may well be the way to go.

This type of work on most BMW's does tend to be costly...sorry!

[Bfab]

Thanks for the reply.

Ill prob go for the latter option seeing as funds are low at the mo.

This is prob a daft question but was wondering if a B25 head will fit as a replacement

[Bfab]

Thanks for the reply.

Ill prob go for the latter option seeing as funds are low at the mo.

This is prob a daft question but was wondering if a B25 head will fit as a replacement

No problems with the oil pressure light.

[daimlerman]

This is prob a daft question but was wondering if a B25 head will fit as a replacement

Yes,but(there's always a but with this type of question!)

2ltr and 2.3ltr(320/323)use a head we call 731,this is pretty much a hemi-head design to suit the flat-topped pistons that these engines use.

2.5ltr(325)use a head we call 885,this comes with a 'swirl' pattern chamber to suit the oddly shaped pistons used in this engine,but this head does have slightly bigger valves.

Yes,the 325(or 885)head will fit the smaller engine,but the bigger valves and odd shaped chamber will not improve performance,you will probably use even more fuel than you do at the moment.

Head identification.
On the inlet side,you will find the casting number,either 731 or 885.
Additionaly,the 885 head will have 2.5 or 2.5/2.7 cast into the exhaust side.
HTH

[bmw320iSE]

how is the head damaged??

cracked/warped?

[Bfab]

Cheers daimlerman

Better sticking with original head seeing as fuel aint gettin any cheaper!

The actual head is okay just the insides need attention. Not sure whether to rebuild or go for scrap one.

[daimlerman]

This may well help you;
http://www.e30zone.net/e30zonewiki/inde ... inder_Head

[Bfab]

This may well help you;
http://www.e30zone.net/e30zonewiki/inde ... inder_Head

Thanks

Very informative. Interesting to know what my mech will be doing as I would not atempt to do this due to lack of experience.

Will rebuilding the head effect the bottom end

[toby]

Before you get scared off by the insurance implications of an engine swap, speak to your insurance company. Some alterations do not incur any fee at all. It's free to ask at least.

An engine swap to a 325i would be worth the money, especially for your heavy cabriolet. I helped out with a swap last year on a lovely metallic green 320i cabriolet with a knackered engine and it was replaced with a high compression 2.5 lump and the difference in performance, especially considering it was automatic, was a revelation for the owner. Get a high compression engine for the swap if you can.

I wish you luck with whatever you decide though.

[78gizmo]

If you decide the 2.5 route i have got a good high compression lump as Toby sugested above. I removed it from my rotten 320i which had received the same upgrade. It runs great but due to the engine transplant i havent any history for it, so i am only after £150 for it. Send me a pm if interested.

[toby]

This is the way to go. Include all the bits required, ECU etc and it's a day's work for a massive upgrade. Forumtastic!