2.7 / 2.8 build aritcle

[ChrisBarns]

apparantly there was a step by step guide to 2.7 and 2.8 m20s in a BMW mag recently. Which mag was it and which month?

I hope its less confusing than trying to follow some of the threads on here!

Thanks

[bss325i]

Total BMW mag, March 2007 issue, page 70. Was written by Andyboy from this forum!.

[ed325i]

Which are looking at building 2.7 or 2.8 ?

[ChrisBarns]

can't decide. Will read article. There is still an M52 possibility too.

I like the idea of building up an engine over time (i get a lot of time off) as I haven't done it for years and have only ever rebuilt to standard (and i don't think I've ever done one modern enough to have an over head cam!) then swap it in when finished. Hoon about knowing its all my own work etc. But I need to do more research about running ordinary unleaded (I already spend £200 a month on petrol) or possibly LPG in a 2.7 / 2.8. The idea of an M20 feels more natural and i like the idea of the sort of mods that might have been made when the car was new. Guess I'll read the article and then start some kind of 2.7 vs 2.8 vs M52 2.8 fight on here!

Anyway engine is summer project. Car needs to stop / corner / look nice first. Then I'll decide. I just thought I'd get the article while it was still current.

[ed325i]

I spend about that on petrol in the e34.
I am building the 2.8 as its easyer than the 2.7

[ChrisBarns]

Ed - you're not that far from me either. When youve finished the 328 can i come over for a spin?

[B7]

I've been looking into this and as far as I can see the jury's still out as to the best way to go. I'd love to see a rolling road comparison between a well sorted 2.7 (such as a genuine Stannard car) and an m20 based 2.8 using the M52 crank). I'd also like to see proper performance figures using timing gear (not some muppet sitting in the passenger seat pushing the OBC buttons). We all know the 2.7 is a great conversion but how does the 2.8 compare really.

I've heard so many stories like the 2.8 route don't make the power, the 2.7 is a pain due to decking the block etc. etc. etc. That article actually (as far as I can remember) did not quote any figures (BHP vs Torque and when max Torque is achieved etc.).

Then, if originality is not your priority (which it is mine), theres the M30 route!! Decisions decisions

[Jon_Bmw]

B7 have a look the at 0z's 2.7 build thread. 2 independant rolling roads at about the 225bhp mark. This isn't an average homebuilt 2.7 though. This was properly sorted and specced by resident hero Antus

[ed325i]

Ed - you're not that far from me either. When youve finished the 328 can i come over for a spin?

Yes you can

[andrewpany2002]

is this issue of total bmw still on sale ?

[ed325i]

B7 have a look the at 0z's 2.7 build thread. 2 independant rolling roads at about the 225bhp mark. This isn't an average homebuilt 2.7 though. This was properly sorted and specced by resident hero Antus

I have had a word with Ant about a cam and its going to be the same spec as the one in oz's 2.7 so it will interesting to see what the diff is in power if any.

[Ant]

The jurys still out on the 2.8, the one in Adams car was a victim of polished bores during running in, hence low ring seal and reduced HP as a result, good torque though.

Scotts 328 monster is an unfair comparison, MBE and ITB's mean its too high spec to be a valid benckmark.

biggest "cost saving" for the 2.8 build is the vernier is not compulsory, so £100 to spend getting the nose spacer made up The block will still need a haircut imho, to retain the stock squish.

@ Jon cheers for the props dude

[ed325i]

The block will still need a haircut imho, to retain the stock squish.

How much needs taking off ? I didnt think you had to.
would it be best to skim the block or the head ?

[Ant]

you dont HAVE to Ed. will work fine without, but if I was building one, it'd be getting a trim for defo.

I posted my ramblings as to why on one of the other threads, even some mathematics

[ed325i]

Found it Ant to get the CR on the 2.8, its 0.5mm off the head, or block to give the same squish band as the stock M20B25K engines.

[Ant]

don't forget to work the CR out dude !

retain the stock squsih by all means, but measure everything 1st, and allow for the extra 300cc's in the CR calcs

you can do it with percentage increase over the quoted figures for the B25 as a guide

[jonb]

Your right.

To much conflicting advise and confusion if you use the search on here, is its been gone over to many times.

Read the total article, or do what oz did and bring your car to ant, that cuts out all the dirty hands and the grief from the missus. Oh and 200+ bhp...

[B7]

Ant's just varified exactly what I'm saying. We need some sorted cars to compare. I'd like to see:

A good properly built 2.7 (this ones been done fo so long it's pretty firm now as to whats required and oz's sounds perfect)
A 2.8 without the block decked.
a 2.8 with the block decked.

Ant's just thrown another quandry in for me as thats the first time I've heard of taking anything off a 2.8 block.

Ant. What would be the difference between taking the metal off the head and taking it off the block. Surely taking it off the head will reduce the combustion chambers and hence riase the CR further than just taking the same amount off the block? Or am I being thick!!

Similar to ChrisBarns I used to build Mini engines and the odd kent ford (plus one essex V6 ) but it's been a long time. Now wheres the emoticon for "Old Bastard!"

[dibdab]

Taking metal from the block will increase the compression ratio at a greater rate than skimming the head. This is because the head is domed and the block is cylindrical

[ChrisBarns]

b7 we need an old gits club. what was wrong with push rods anyway. and carbs for that matter...

[ed325i]

The last engine I re built was a mini engine.
I know where there is a 525e (2.7) engine if you want one.

[B7]

MY HEAD HURTS!!!!!

This is why I'm just doing a head rebuild for now, until I'm sure of which way to go.

Old gits club? I'm offended. I'm "only" 43 ............... tomorrow.

[Ant]

Gimme a budget and I'll build one for ya dude, not as much fun as a fully DIY affair( for you @ least) but gets the desire fulfilled

2.8 in a crate has a ring too it no ???

[Simon13]

surely it's better to deck the block a little and use a vernier? this will give you more tweeking power too after the engine is running with a vernier and it's safer than skimming massive amounts off the head

there are not enough 2.8 builds out there to really compare! shame as it could be another good way of tuning an M20 slugger

[B7]

there are not enough 2.8 builds out there to really compare! shame as it could be another good way of tuning an M20 slugger

Law of averages means that 2.7 cranks must be drying up soon and there must be loads of nicosil m52's laying about out there. I would think the 2.8 must be the natural step forward for the M20.

[Andyboy]

imho you don't need to deck the block for the 2.8. When I did Adams engine the pistons came right to the top of the block as per normal. Using a standard head gasket the compression ratio was still nice and high. Ant is talking about literally thousandths of an inch, not 2-3mm.

This is because:

The 325i and Eta use pretty much the same block. The Eta block is allegedly 0.5mm taller although I think this is the early blocks with the big core plug at the back.

The 320i, 323i and Eta use 130mm long con rods. The 325i uses longer 135mm rods.

Use a 2.7 crank in a 325i and the pistons poke out @ 2.5mm

Use the shorter rods and the pistons fall short of the top of the bore - that's why you skim the block down.

Use the 2.8 crank whose stroke is 3 longer in a 325i block and the pistons come perfectly to the top of the bore. This isn't bullshit pub talk but fact. I've done both the engine and the measuring - the edge of the piston comes a fraction over the top of the bore as needed. Use an early )pre 9/85) Eta 525e block and you may need to skim a bit off but it's in no way essential. Later Eta blocks are the same as a 325i. You'll lose so little in the way of compression. But when you're building an engine from scratch you always give a block a light 2-5 thou skim to make it perfect.

[Ziggy]

For someone who say had a pre-'88 325i, located said 2.8 crank (& did the work on it) & the rods... what then?

Having never rebuilt the internals of an engine, I don't know how involved it has to be... what has to come out to change the crank & rods? I get that rebuilding everything's clearly a good idea, but I'm just wondering what the minimum is - more out of interest than anything else.

Oh & on another note, I heard of someone changing the cam on a 2.5 with the head in place - doable or no?

[liam012]

re the cam - rumour has it it will come out via the front grill being removed and some wiggling.
havent done it myself though

[Ziggy]

re the cam - rumour has it it will come out via the front grill being removed and some wiggling.
havent done it myself though

That's what I heard too... would make finding a bargain priced cam all the more tempting

Anyone else?

[Ant]

Cam will pop out the front with grille, rad and one engine mouynt removed( mount not always required... )

Get those CatCams on order

[Ziggy]

Cam will pop out the front with grille, rad and one engine mouynt removed( mount not always required... )

Get those CatCams on order

Distinctly tempted!!

So go on... what do you have to do (/buy) to change a crank & rods?

[Simon13]

i've got my catcam!

ziggy you would need to drop the engine out to do it!

from the top of my head

oil pump, good idea imo, shells,rings,big end bolts, main bearings the bolts for these? machine work,headgasket set and bolts,sump gasket and probably more!

[oguz327]

i've got my catcam!

ziggy you would need to drop the engine out to do it!

from the top of my head

oil pump, good idea imo, shells,rings,big end bolts, main bearings the bolts for these? machine work,headgasket set and bolts,sump gasket and probably more!

Things you might as well do while your there too, waterpump, engine mounts, clutch etc...

[ed325i]

My 2.8 crank will be here to day
I am going to get a cat cam

[mrLEE30]

can anyone please tell me how to identify a 2.8 crank over a 2.5/2.0/3.0 crank please... also getting ready to build one up, happy days going from a 2.0 slush box to a 2.8 manual... so even 150hp fomr my 2.8 will be great!!!

BTW i am using the older (86) 325 as a base... i assume its ok, i have not yet checked where the Crank sensor is but i assume its the later type, but what about the older pistons/older engine CR are there any issues here?

Also plan to change oil pump/main bearings/new con rod bolts/ and general bits, but any need for conrod (top and bottom) bearinsg to be changed too? engine done around 100K

cheers all

mrlee