2.7 conversion practicality?

[Dr Firefly]

Seen a lot of people go for these conversions, but would like to hear from people who've done them and how successful they were.

At present I've got a M20B20 in, and debating between going the simple route and dropping in a M20B25, or going for a 2.7 conversion. Decided I'm not interested in any more modern engines or in an M30 - want to keep the car as original as possible as regards looks.

Will I notice a difference between having a 325 and a 327? Big performance improvement? How about fuel consumption and MOT emissions tests etc? And finally... and this is most important - how far have people driven one of these after the conversion - does it last as long as a BMW designed and tested engine, or will it die within 20k miles or so?

Cheers, and thanks for what I'm about to receive.

[ed325i]

What about a 2.8 ?

[Dr Firefly]

Thought about it, but would like to keep an E30 engine in - partly because any insurance company won't be able to tell any difference. Also heard mixed things about the 328 conversion, and I'd like to keep it all as simple as possible. Also like the idea of a full engine rebuild - apart from the price! But I wasn't sure if the engine would actually last as long - surely mixing and matching bits from different engines makes it more likely to fail? That's why I was wanting to know if anyone's actually used a 327 as an every day car for over say 30k without any problems. Don't want to replace my trusty 320 with a 327 that's sat on a drive in bits while I catch the bus!

[Templ8e30]

I've got a 327i, built it myself over 2 years and 30k ago. Had zero trouble with it (touch wood).

The difference between a 325i and my 327i is as big as the difference between a 320i and a 325i.

Fuel consumption is a bit steeper than the 320i/325i but not much, no bother with emissions.

Agreed the 2.8 is an easier option.

Cheers,

Iain

[ed325i]

Thought about it, but would like to keep an E30 engine in - partly because any insurance company won't be able to tell any difference. Also heard mixed things about the 328 conversion, and I'd like to keep it all as simple as possible.

2.8 m20 easyer to build then a 2.7.

[daimlerman]

My 327 has now run around 6000miles.I used a 525e crank/rods/pistons in a s/h 325 block,320 sump,320 head with 325 cam,fed via MillerMAF,325 T/B,325 manifold and injectors.Zone chip,modified by Miller to suit their MAF. 3.64 open diff.All inserted in an 89 4 door 320ise.Result?I have a very quick car that I use every day,the overtaking ability is awesome,instant grunt from 2000rpm in any gear.I am averaging 33+mpg in a mix of short trips when er indoors uses it and my 41mile round trip via country lanes to work.Most weekends it gets a blast to Hickling Broad in Norfolk which is mostly A road single carriageway,125 miles average time is 2 1/4 hours.If I was to do it again,I would look into the costs of a 2.8,I would also think carefully about Ants comment regarding boring a 2ltr block to 84mm(this way you also keep a 2ltr engine number...)Do check a 525e crank for wear,my was well worn and cost £85 + shells and new piston rings cost £98.I have no idea of the bhp of my engine,a best guess would be in the order of 180/190bhp,quite a boost from the stock 320i 129!!

[Dr Firefly]

Thought about it, but would like to keep an E30 engine in - partly because any insurance company won't be able to tell any difference. Also heard mixed things about the 328 conversion, and I'd like to keep it all as simple as possible.

2.8 m20 easyer to build then a 2.7.

Sorry, I think I made a mistake then. I thought that a 2.8 had to be an M50, M52 or something? I didn't know you could make an M20 2.8? Anyone got links to relevent threads, nothing popping up on the search yet...

[Dr Firefly]

My 327 has now run around 6000miles.I used a 525e crank/rods/pistons in a s/h 325 block,320 sump,320 head with 325 cam,fed via MillerMAF,325 T/B,325 manifold and injectors.Zone chip,modified by Miller to suit their MAF. 3.64 open diff.All inserted in an 89 4 door 320ise.Result?I have a very quick car that I use every day,the overtaking ability is awesome,instant grunt from 2000rpm in any gear.I am averaging 33+mpg in a mix of short trips when er indoors uses it and my 41mile round trip via country lanes to work.Most weekends it gets a blast to Hickling Broad in Norfolk which is mostly A road single carriageway,125 miles average time is 2 1/4 hours.If I was to do it again,I would look into the costs of a 2.8,I would also think carefully about Ants comment regarding boring a 2ltr block to 84mm(this way you also keep a 2ltr engine number...)Do check a 525e crank for wear,my was well worn and cost £85 + shells and new piston rings cost £98.I have no idea of the bhp of my engine,a best guess would be in the order of 180/190bhp,quite a boost from the stock 320i 129!!

How much did all that cost? Sounds pretty good - also interested in the idea of boring out a 2ltr engine - where did Ant talk about that? Thanks a lot for the reply, that's some good information in there that could be useful...

[daimlerman]

Machine shop work on the head(valve guides,new valves,skim)£350.Machine shop work on crank,new shells new piston rings £300.Gaskets,head bolts,odds and ends from GSF £100,other oil seals,odd gear linkage bits from the stealer £120.Miller MAF about £300.My blood sweat tears and sweary words,priceless!!I cannot see how a proffessional would charge less than £3000 to obtain parts,machine,build and install...using a 2.8 crank may save a little,and give a little more power.There is lots posted on these engines,the problem is digging it out.The m20 its self is resonably easy to work on,needs care to get things just right,but it can be done by one person working alone with reasonable facilities.I enjoyed the job,and I also enjoy the result.

[Simon13]

just find the pistons you want to use and retain your 2.0 block. Send it all off to the machine shop and they can bore out each bore to the exact right size for each piston. This won't be cheap at around £30 per bore to do, BUT it's the best way for compression and factory fresh bores again.

hth

[Ant]

or bring me a nice fresh 2 litre block and rods, some coin and I'll do it for you

have a spare 2.8 crank, and a mint set of post 88 slugs, add in a decet cam and you'll have a brand new, reliable engine that wil last for 150K if looked after, the strokers wont do quite the mileage of the B25 due to the higher pston speeds and loads, but for the extra go, I think its a worthwhile compromise

you cant have power and longevity, you have to balance them.

[andrewpany2002]

how comes its better to use a 320i head for this conversion ? and would it be better to use eta crank pistons and rods in a 325 block or leave them in a 525e block ? also if i have eta pistons that have just come out of a 525e thats done around 100k is there any need to change pistons rings and bigends since they only rev up to 4000rpm correct me if im wrong ?

thanks

[daimlerman]

325/525e blocks are the same.The 320i head has the same combustion chamber and valve size as the 525e head. The 525e cam and cam bearing layout is different to the 320i head.You can modify the eta head to work by swapping cams,BUT,the lubrication to the cam in the eta head needs modifying,I have no experiance of this.I am looking for an eta large valve head to play with at the moment.The piston crown on the 525e and 320i is a similar shape,this is why the 320i head works best.To gain from using the larger valves in the 325 head you need to use the 325i pistons,which opens up a whole new set of problems that I decided not to tackle.I would like to try 525e head with modified cam bearings and 325 valves....gets addictive,this tuning!!I respect Ants view as regards using a ^decent cam^,but this will move the power further up the rev range,give more ultimate power,but the joy of this motor is the huge torque boost at main road overtaking speed,you pays your money,you makes your choice! And do not forget,to make this work properly,you need a zone chip.

[andrewpany2002]

what kind of problems would using a 325i head instead of a 320i head bring up ?

[toby]

Andrew they are not problems as such but vary the specific approach of the build. Using the 325i head, as daimlerman said, means using the 325i pistons (to avoid possible the valve/piston clearances being too small with the eta pistons). The 325i pistons have handy cut outs in them. Using these pistons (rather than the eta ones) means the block has to be skimmed as the pistons are shorter.

When the block is skimmed down the timing is effected (the block becomes a bit shorter) and a vernier pulley has to be substituted in place of the top pulley to reset and correctly compensated the timing. The downside is extra cost but the upside is the extra power that the 325i piston/head ensemble design delivers.

Like most things, it's a question of what you want to buy and how much you want to spend.

Correct me if I'm talking sh!te here please!

[daimlerman]

Thanks Toby,I was too tight fisted to take that route...it was the money over gain equation,it did not work for me. The weak point of the M20 is the cylinder head,the 325 version does seem more vunerable to cracking than the others,although my score is one all so far!

[Simon13]

again depending on budget custom/alpina/hartge pistons are nice and you can use 325i rods with eta/324td crank. Along with a 2.5 head. No block decking and vernier pulleys needed either. So it's a swings and roundabouts one because the cost of these pistons is not cheap but will save you building the entire bottom end up, then measuring how much needs to come off the block, getting it decked then building it all back up again!

Touch wood i've had 4 b25's and the worst so far has been a snapped rocker on my miley touring

[toby]

That's a really cool bit of alpina/hartge hidden information Simon, cheers.

Your rocker only snapped under serious provocation though didn't it?

Firefly2005 my suggestion would be to have your 320i block bored out so it's bigger, clean and 'as new'. Buy a new 525e crankshaft and shells. Fit the pistons of your choice to match the head and the perfomance you want.


You can then keep your existing head and add another camshaft, say the 323i, 325i or fast road cam like a catcam. Or get a 325i head and have the catcam option again.

Performance varies. Question is what kind of driving do you do? What power/torque delivery do you want? Low down torque is what this does best.

[tim-ix]

Ant, or anyone else who knows,

Would I just need my existing M20B25 engine plus the crank from an M50 2.8 to make a 2.8 litre M20 then?

My head hurts.

[andrewpany2002]

thanks toby i understand now , im looking to build one slowly as a project. if i used the 325i head and piston method i assume that i would get abit more power because of the larger valves, however is the power difference from taking this route rather than using eta pistons and 320i head worth the hastle ? and how about using slightly longer conrods with the 325i pistons so that they come up a bit further ?

[toby]

Tim, yes but it's an M52 2.8 crank.
Plus a bit of engineering to make the crank fit in the block. A nose for the crank and oil seal modification. Shorter con rods (320i 323i ones) also needed.

There's still debate as to whether the block needs skimming or not.

See this thread
http://www.e30zone.net/modules.php?name ... sc&start=0

[toby]

thanks toby i understand now , im looking to build one slowly as a project. if i used the 325i head and piston method i assume that i would get a bit more power because of the larger valves, however is the power difference from taking this route rather than using eta pistons and 320i head worth the hassle ? and how about using slightly longer conrods with the 325i pistons so that they come up a bit further ?

Andrew stop farting about and answer my questions first those impact your questions. If you want the extra power then it is up to you to decide if it is worth the hassle. (It is all hassle though really isn't it? I'd want the ultimate result. I'd use 325i internals. But as daimerlerman has said he didn't find it to be worth his while Oz spent out his money to get the 2.7 that he'd dreamed of since he was a lad, so opinions and financial commitments vary.)

I saw the ultimate 2.7 build of Oz's car that Ant at A-Tech did and it's power is tested now and speaks well of using the 325i pistons and head. This is close toward the Alpina way of doing things as Simon has said.

I drove some Alpina 2.7s years ago and they were fantastic. I also drove 525e 2.7 models too and loved their low down torque which was superb around town (got stopped by the police many times in the 525e cars as they get up to speeding from standstill so easily!).

It all ends back with personal requirements and coinage.

You ask 'longer con rods?' but the fine tolerances dictate that the ways described above are the established ways of doing the conversion.

It depends how confident you feel with a spanner too I suppose. If you are doing this at home you could avoid the need of a machine shop (by not using the 325i pistons) as a bolt together job if that is what you want? There is a recepie for this.

[tim-ix]

Thanks Toby. I just found that thread but it all seems a bit up in the air as to what the best way to go about building a mix-n-match 2.8 is. I'm pretty sure mrlee never got a straight answer.

I may watch developments for a while until some concensus emerges. If that happens.

[Dr Firefly]

That's a really cool bit of alpina/hartge hidden information Simon, cheers.

Your rocker only snapped under serious provocation though didn't it?

Firefly2005 my suggestion would be to have your 320i block bored out so it's bigger, clean and 'as new'. Buy a new 525e crankshaft and shells. Fit the pistons of your choice to match the head and the perfomance you want.


You can then keep your existing head and add another camshaft, say the 323i, 325i or fast road cam like a catcam. Or get a 325i head and have the catcam option again.

Performance varies. Question is what kind of driving do you do? What power/torque delivery do you want? Low down torque is what this does best.

Why didn't BMW make an M20B27 or an M20B28? Just because it raised the cost of the engineering so much? Or are they not as good all-rounders as the M20B25s?

I think what I would want would not be a particular bias towards either low-end torque or high-end revs but just an all-rounder that would be better at every range than the M20B25. What would be the best option for that in people's view? Looking at the older threads, 327s are better at high revs, without as much low end torque, while the opposite is true for a 328. So is there anyway way of getting a reasonable improvement in both, while keeping a similar level of reliability to the original engine?

Interested in what you were talking about Ant, what kind of price are you talking for that mate? And would I need new AFMs, ICVs, etc. What kind of ball-park figure are we talking to get a tired 320 bored out to a 328, and back in the car idling perfectly and feeling like a new engine?

[toby]

I suppose they didn't build those engines you mention for various boring marketing, research, insurance implications.

The 2.7 is usually less easy revving without a lairy camshaft than a 2.5, with more torque and power.

Not that many 2.8 have featured but I know of one on the Zone. The 2.8 conversion is said to be the best all rounder for road use.

[ed325i]

what the best way to go about building a mix-n-match 2.8 is. I'm pretty sure mrlee never got a straight answer.

M52 2.8 crank with a spacer made for oil seal.
M20 2.0 / 2.3 or 525e con rods.
M20 2.5 pistons early ones are best.
M20 2.5 head.
A nice cam from cat cams (Ant)
Chip from Ant.

[daimlerman]

The answer is that there is no straight answer!!...If I was to do this again...I would be looking at the spec posted by ed325i very,very closely.Simon13 gave a reasonable rebore price and the advantage of that is beyond dispute, unless one is fortunate enough to come across a s/h block with sound bores.The joy and the snags of the Alpina and other similar cars are the exclusive parts that they use...Alpina exhaust £1300 (if available)325i exhaust from GSF £132.My wallet could never justify Alpina pistons...Was it Ant who said that you cannot have a champane engine for beer money?Uprated cams are around £400,but will give more top end,not what I wanted.At the end of the day,you pays your money and makes your choices.

[toby]

cat cams for the M20 + M30 retail about £230 from Ant

[daimlerman]

GSF 325i cam £80....

[Ant]

325 cam is OK, but why go to the expense of the 8% capacity hike, and then strangle it with a soft cam profile ?

The idle quality will suffer, granted, but simply raising the base idle speed to 900 rpm( easy 1 wire connection on the A/C plug ) will sort that minor gripe.

[daimlerman]

Ant,tell us a little more about catcams,I stopped looking at aftermarket ones largely due to the cost/result balance did not work for me.What I like most about my build is the instant overtaking grunt available from 2000rpm,can a catcam improve this?I am too grown up to be a boy racer,anything that only shows an improvment above 5000rpm at the expense of low speed drivability(er indoors drives this car as well)would not suit.I am starting to think that the current head has cracked,probably around an exhaust port,so may be in a position to try something different over the next few weeks.

[tim-ix]

Quote:
what the best way to go about building a mix-n-match 2.8 is. I'm pretty sure mrlee never got a straight answer.


M52 2.8 crank with a spacer made for oil seal.
M20 2.0 / 2.3 or 525e con rods.
M20 2.5 pistons early ones are best.
M20 2.5 head.
A nice cam from cat cams (Ant)
Chip from Ant.

Thank you Ed. This is exactly the sort of thing I needed. There will of course be a whole load of other sundry costs I suppose, stuff like main bearings, cylinder head bolts, gudgeon pins, a new oil pump etc etc etc.

This could get pricey, but then nothing good in life comes free I suppose.

[--alpina--]

I was offered an E36 3.2 M3 crank which is very rare... and am thinking of rebuilding an M20 block with Mahle custom pistons and also an `O` ring for the crank modification so that is going to be another sweet `Fast ` project under my belt!! let ya know how this goes... and cant F-----G wait.. was offered a vortex superchager conversion so who knows how much power will be released..

j