M20 B20 Head Rebuild

Moderator: martauto

Post Reply
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Tue May 17, 2011 11:59 am

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.
:o:
Image
320 Cabriolet 91
User avatar
toby
E30 Zone Addict
E30 Zone Addict
Posts: 3609
Joined: Thu Aug 11, 2005 11:00 pm
Location: Kent

Tue May 17, 2011 12:17 pm

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)
Image
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Tue May 17, 2011 12:24 pm

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.
Image
320 Cabriolet 91
User avatar
toby
E30 Zone Addict
E30 Zone Addict
Posts: 3609
Joined: Thu Aug 11, 2005 11:00 pm
Location: Kent

Tue May 17, 2011 5:13 pm

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.
Image
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Wed May 18, 2011 10:14 am

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 :?:
Image
320 Cabriolet 91
User avatar
eta
E30 Zone Regular
E30 Zone Regular
Posts: 356
Joined: Fri Oct 26, 2007 11:00 pm
Location: Glemsford Suffolk
Contact:

Wed May 18, 2011 10:32 am

Also remeber an engine swap will affect your insurance a head rebuild won't.
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Wed May 18, 2011 10:46 am

I didnt realise that. Prob best to stick with new head. Will rebuilding head effect bottom end tho :?:
Image
320 Cabriolet 91
daimlerman
**BANNED**
Posts: 15968
Joined: Mon Feb 27, 2006 11:00 pm
Location: Grumpy Old Man

Wed May 18, 2011 11:10 am

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!
Youth is wasted on the young.
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Wed May 18, 2011 11:21 am

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 :?: :o:
Image
320 Cabriolet 91
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Wed May 18, 2011 11:29 am

Bfab wrote: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 :?: :o:
No problems with the oil pressure light.
Image
320 Cabriolet 91
daimlerman
**BANNED**
Posts: 15968
Joined: Mon Feb 27, 2006 11:00 pm
Location: Grumpy Old Man

Wed May 18, 2011 11:32 am

Bfab wrote:
This is prob a daft question but was wondering if a B25 head will fit as a replacement :?: :o:
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
Youth is wasted on the young.
bmw320iSE
E30 Zone Newbie
E30 Zone Newbie
Posts: 100
Joined: Thu Jan 13, 2011 11:00 pm
Location: Essex

Wed May 18, 2011 3:49 pm

how is the head damaged??

cracked/warped?
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Thu May 19, 2011 11:54 am

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
**BANNED**
Posts: 15968
Joined: Mon Feb 27, 2006 11:00 pm
Location: Grumpy Old Man

Thu May 19, 2011 12:07 pm

Youth is wasted on the young.
Bfab
E30 Zone Newbie
E30 Zone Newbie
Posts: 40
Joined: Fri Jul 30, 2010 11:00 pm
Location: London

Thu May 19, 2011 1:27 pm

daimlerman wrote: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 :?:
Image
320 Cabriolet 91
User avatar
toby
E30 Zone Addict
E30 Zone Addict
Posts: 3609
Joined: Thu Aug 11, 2005 11:00 pm
Location: Kent

Mon May 23, 2011 8:03 pm

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. :cool:
Image
User avatar
78gizmo
E30 Zone Regular
E30 Zone Regular
Posts: 265
Joined: Fri Nov 16, 2007 11:00 pm
Location: Torbay, South Devon

Tue May 24, 2011 7:15 pm

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.
Image
User avatar
toby
E30 Zone Addict
E30 Zone Addict
Posts: 3609
Joined: Thu Aug 11, 2005 11:00 pm
Location: Kent

Wed May 25, 2011 6:37 pm

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!
Image
Post Reply