M20 rebuild DIY possible?

[Rtaylor2208]

I have been offered a M20 2.5 for free but on one condition. I dont sell it. It's a friend of a friends that was bought for a kit car that never got finished. And has been stood for about 4 years, done 78K but very limited history.

As a very long term project I'm considering rebuilding after being inspired by a few of the threads in the engine swaps section.

Realistically if I do all the work myself apart from getting the head skimmed by the pros is it possible for someone with absolutely no experience of doing something like this before?

Tools wise I have a good selection of sockets, spanners etc. is there anything specific tool wise I would need and ball park what would I be looking at in terms of parts and any specialist tools?

I really fancy the challenge but don't wont to spend hundreds of pounds to realise I really don't have the skills to finish it.

[Rav335uk]

You'll need a valve spring compression tool if you don't have one.

[Rtaylor2208]

Definetly don't have one if them Rav

[daimlerman]

M20 is a lovely engine to pop your engine building cherry with.

It comes apart in a logical fashion with little hidden drama.

However,the front crank bolt,the big 22mm one,needs slacking off BEFORE you remove the engine,the swine is tightened to something like 400ft lb,so is all but impossible to move with the engine on a stand or sat on the garage floor.
So if this engine is still in the kitcar chassis,take a battery with you and a long breaker bar and use the starter motor to shock the thing free!

Engine bits are suprisingly expensive,individual parts do not sound pricey,but twelve rocker arms at £12 each and twelve valves at £8 each soon add up(prices are gtuess work)
You will need some special tools,pison ring compresser and valve spring compresser spring to mind,torque wrench as well.

Other than that,if you can strip a front strut and a door mech,you can certainly cope with an engine.

[Rav335uk]

The crank bolt is doable on an engine stand, I removed the M30 one with some heat and alot of brutforce.
You ned to lock the flywheel to do it though.

[ross2009]

them crank nuts are a beast i snapped 2 tommy bars i had a big old tooling vice on it and hitting that with a sledge that snapped aswell i cant remember how i got it undone now

[e30den]

A bentley's workshop manual is well worth buying if you have'nt already got one.

[Rtaylor2208]

Bentley manual and 2 torque bars in my garage, the big one is 3ft long and great for anything remotely stubborn.

Unfortunately the engine is on a stand as the kit car is up for sale with a ford lump in it as he had the bits needed to get it working.

Compressor tools will nee to be purchased. The cost of the engine parts is doable even if pricey as this will potentially take me forever to do. Wifey is past due and I'm thinking this would be something I can work on in the shed over the summer as the garage is full of E30 bits to be put back onto the cabby.

Lots of shiney new bits ordered yesterday but more required to get the cab back on the road.

[Rav335uk]

If you can lock the flywheel, you can undo the crank bolt.

http://www.ebay.co.uk/sch/i.html?_trksi ... &_from=R40

[goosiegander]

At sub 80k nothing should need rebuilding.

If there is no sign of H-Gasket failure then swap the headbolts to torx head type and adjust the valve clearances.

Build up the ancillaries and then BOSH! Engine can go in,

I wouldn't be entertaining a rebuild until at least 150k plus... Shells should all be good unless there is swarf in the sump, have the sump off and renew the gasket and if you see anything suspect check the rod shells and crank end float against the specs in the manual.

Hope that helps

[Brianmoooore]

At sub 80k nothing should need rebuilding.

If there is no sign of H-Gasket failure then swap the headbolts to torx head type and adjust the valve clearances.

Build up the ancillaries and then BOSH! Engine can go in,

I wouldn't be entertaining a rebuild until at least 150k plus... Shells should all be good unless there is swarf in the sump, have the sump off and renew the gasket and if you see anything suspect check the rod shells and crank end float against the specs in the manual.

Hope that helps

This! Run it for another 150k, then you might just find a bit of wear in the exhaust valve guides. Bottom end should still then be fine, if you don't skimp on servicing and oil quality.

[daimlerman]

At sub 80k nothing should need rebuilding.

If there is no sign of H-Gasket failure then swap the headbolts to torx head type and adjust the valve clearances.

Build up the ancillaries and then BOSH! Engine can go in,

I wouldn't be entertaining a rebuild until at least 150k plus... Shells should all be good unless there is swarf in the sump, have the sump off and renew the gasket and if you see anything suspect check the rod shells and crank end float against the specs in the manual.

Hope that helps

This! Run it for another 150k, then you might just find a bit of wear in the exhaust valve guides. Bottom end should still then be fine, if you don't skimp on servicing and oil quality.

I get the impression Russ wants something to tinker with once the new baby is taking up is 'er indoors time and energy!

Golden oppotunity to build a stroker....

[snakebrain]

I'm following this with interest. Engine building is a bit of a dark art to me. I'd be tempted to buy an M30 and do a rebuild just as a learning experience. But I'd be in the same boat as the OP with not wanting to discover I'm way out of my depth halfway through..

[bmw9818]

same id love to be able to build an engine, i did a head gasket on an m20 thats as far as ive gone,

bottom end pistons, boring it out and rebuilding the cylinder head as well would be something else!

crank bolt could be undone with a airgun, thats how i did my subframe and flywheel bolts

[Brianmoooore]

At sub 80k nothing should need rebuilding.

If there is no sign of H-Gasket failure then swap the headbolts to torx head type and adjust the valve clearances.

Build up the ancillaries and then BOSH! Engine can go in,

I wouldn't be entertaining a rebuild until at least 150k plus... Shells should all be good unless there is swarf in the sump, have the sump off and renew the gasket and if you see anything suspect check the rod shells and crank end float against the specs in the manual.

Hope that helps

This! Run it for another 150k, then you might just find a bit of wear in the exhaust valve guides. Bottom end should still then be fine, if you don't skimp on servicing and oil quality.

I get the impression Russ wants something to tinker with once the new baby is taking up is 'er indoors time and energy!

Golden oppotunity to build a stroker....

Maybe, but at least start with something that's a bit nearer needing a rebuild. There can't be that many untouched 2.5 M20s around that are barely run in at 80k miles.

[Rtaylor2208]

Thanks chaps, Malc is bang on the money, this is an interest to further my know how rather than it has to be done as a necessity.

How good its is, is an unknown as it has stood for a good few years and was only heard running for about 15 minutes before being removed.

I agree with Brian's point about doing this on something much more leggy but I wouldn't get one for free which is really my justification in potentially taking this on.

[Morat]

I see what you're saying but what's the point in taking something apart to say "Yep, in spec" and bolt it up again?
Tell you what, I'll swap you for my 150k engine so you can have some fun

[goosiegander]

At sub 80k nothing should need rebuilding.

If there is no sign of H-Gasket failure then swap the headbolts to torx head type and adjust the valve clearances.

Build up the ancillaries and then BOSH! Engine can go in,

I wouldn't be entertaining a rebuild until at least 150k plus... Shells should all be good unless there is swarf in the sump, have the sump off and renew the gasket and if you see anything suspect check the rod shells and crank end float against the specs in the manual.

Hope that helps

This! Run it for another 150k, then you might just find a bit of wear in the exhaust valve guides. Bottom end should still then be fine, if you don't skimp on servicing and oil quality.

100k on the sport's head plus two bent valves and all the valve guides were within spec, thats pretty good going

[Rtaylor2208]

I see what you're saying but what's the point in taking something apart to say "Yep, in spec" and bolt it up again?
Tell you what, I'll swap you for my 150k engine so you can have some fun

The honest answer is it interests me and will pass the time rather than hitting the gym or god forbid taking up golf. If it was a fooked M20 I would happily do the same.

I could swap it into the cab and rebuild my existing M20 but the fear is I end up with a broken cab and an engine in bits.

If it all goes horribly wrong or takes years I would still have a cab that I can use.

And most importantly it's free

[lhd220turbo]

go for it, its the only way to learn. just be methodical with the approach, take pictures as you go if needed, write stuff down. no better sense of achievment when you hear it running for the 1st time

[HairyScreech]

You know the main bits of the engine will be ok and not need work, thus a stroker crank and rods may well be just the ticket, afterall you wont need to look at rebores or head repairs so the cash for that can go on stroker bits.

If there is nothing wrong with the head or head gasket at this stage then don't skim it. Just check its for surface defects and flatness with a ground straight edge and feeler gauge, too many perfectly good heads seem to be getting skimmed into scrap at the moment.
Never skim a head unless you have to and an engine that uses a card type gasket will need to be warped enough to see with the naked eye and straight edge to need it.

[Simon13]

you should always reface a head once removed. Its a golden rule! They always need a bit of a tickle. Skimming is when your ploughing loads off. A reface is more like 2-3-4 thou to clean up the mating surface

One thing people have forgot is i'd change the spray bar for piece of mind. Saves the top end from wearing prematurely. Or at least make sure the old one isn't blocked in any way

[daimlerman]

Feel that it's only fair to point out that just pulling the thing to bits and having the crank measured for wear,then having it's wearing surfaces polished,valve guides checked out,bores honed(specialist stuff that few of us can DIY)then re-building with new rings,gaskets and oil seals will cost in the region of £1500.

This is why zoner's are suggesting starting with a donk that's already well worn,the added cost of a rebore/new pistons will only add another £500 but will give a motor that will be capable of 250k with the usual servicing.

Those fiqures sort put the 'freeness' into perspective....

Myself?
I'd grab the thing and start searching for a 2.8 crank,modest aftermarket cam and a BTB exhaust manifold!

[Brianmoooore]

I see what you're saying but what's the point in taking something apart to say "Yep, in spec" and bolt it up again?
Tell you what, I'll swap you for my 150k engine so you can have some fun

The honest answer is it interests me and will pass the time rather than hitting the gym or god forbid taking up golf. If it was a fooked M20 I would happily do the same.

I could swap it into the cab and rebuild my existing M20 but the fear is I end up with a broken cab and an engine in bits.

If it all goes horribly wrong or takes years I would still have a cab that I can use.

And most importantly it's free

What's the mileage/condition on this? Engine swap isn't a difficult job.

[Rtaylor2208]

The free M20 is approx 80K on it and came from a manual car.

The one in my cab is approx 106K as it was replaced just as I bought the cab as the last owner seized the original engine after bursting the sump. It's got a good history with it as I have the doner cars service book, its also from an auto and bolted up to a switchable auto in my cab. It's had oil services every year (1000 miles) since I got it, timing belt, pump, tensioner, rocker gasket and d shape seals done about 600 miles ago.

Currently rebuilding the intake side with replacement vacuum pipes, gaskets and all related nuts and bolts.

[Funnybear]

1000k in a year. Blimey. My cab does that in a month.

Interesting reading. Been looking at the old stroker option for a while now. Might have to wait a bit now untill she's up to 150k. Not long to go, at 120 atm.

[gooner1]

I see what you're saying but what's the point in taking something apart to say "Yep, in spec" and bolt it up again?
Tell you what, I'll swap you for my 150k engine so you can have some fun

For peace of mind and a shed full of knowledge gained.

If iv,e read this right, the OP has very little known history of the engine. Does he assume it has had regular oil change or has other wise been treated well?

He has expressed a desire to tinker with said engine and is
in no rush to complete it. What is the worst case scenario if after taking it apart and finding all is how it should be?
A head skim, some gaskets and new head bolts.
Compare that to putting the engine into the car and then discovering all is not well.

I can see the reasons pointed out for not stripping down
an 80000 mile lump, if it had certified history but that doesn,t appear to be the case here.

[Rtaylor2208]

Gooner your correct the freebie donk has some history somewhere that the old boy is trying to find but he can't remember how detailed it is.

Still trying to make sure I have room to store it.

[Rtaylor2208]

Went and view the engine today after being a little preoccupied. Turns out its a M20 but just a 2 litre which was disappointing. The service history was for a 325i but intake is definetly not a 2.5 one.

The owners was less than chuffed as well as he paid good money for it.