e30 sport- 2.8 build?????

[sterlingsilversport]

ok have my sport now a good while and don't wanna sell it on but do want more power, have a spare engine i can build and get ready for transplant but wondering does anyone here have exact details what i'll need and best outcome.

not going turbo or superchange but thinking of the build with a 2.8 block, anyone on here able put me 100%straight please?

[87mtech27]

if its tech 2 go for the 2.8 ltr build not turbo etc, if tech 1 leave as standard.

[sterlingsilversport]

yup its tec2 alright and was thinking exact same as you just mentioned alright,

[jaistanley]

What a load of bufty bullsh!t.. It's just a car, do anything you want to it! Just do it well.

[sterlingsilversport]

yes and thanks for that but as described is what i wanna do and i'm just here looking for bitta help on it please!

[sterlingsilversport]

anybody got any help on the exact aprts needed?

[JT1]

I am thinking of going down the same route as you, i currently have a tech2 sport that i have owned for nearly four years and i don't want to part with it, i have been looking at the 2.7 and 2.8 build, for the 2.8 build you need a crank from a 2.8 single vanos engine and the shorter conrods from a 320 M20 or eta engine (i think), you will also need a spacer for the crank to bring it back to the same spec as the original, i think there is a drawing of the spacer on the WIKI pages along with more info on the 2.8 build. There are a lot of people on this site who know their stuff who can probably give you better information.

[sterlingsilversport]

thanks for the help JT1, will have a look through wiki aswell now

[sterlingsilversport]

no one?

[reggid]

what else would you like to know?

[sterlingsilversport]

pretty much exact parts needed, any probs might run into and if the build is worth doing really?
oh and an estimate on cost if anyone knew would be great, cheers for any help

[march109]

Search it is the hot topic at the moment and everything you have asked has been answered just slightly less than a million times.

[sterlingsilversport]

heard ya had it done yourself, is it a worth while change do ya think?

[jbh]

must admit i did think about doing a 2.8 build but im leaning towards the 2.7 at the moment for the ease of getting parts

[sterlingsilversport]

and is there much difference power wise or parts involved?

[Ant]

2.8 needs the block decked to get the squish as per 325 OE setup , so both require a vernier pulley to get the cam timing 100% right.

horses for courses on this one, I've built loads of 2.7 and 2.8 strokers in the last few years, TBH they are much or a muchness to drive, 2.7 revs more eagerly and the 2.8 just has the edge on torque but it takes a very accurate dyno to spot the difference.

Do it right, do it once, and please , don't use ETA pistons they are just too heavy to be worthwhile using

[sterlingsilversport]

cheers for that ant, best bitta info so far, still doing the maths and deciding on plan of action next anyway as it is,

[jbh]

2.8 needs the block decked to get the squish as per 325 OE setup , so both require a vernier pulley to get the cam timing 100% right.

didint think the 2.7 build needed to get the block decked.. i know theres a few ways of building the 2.7 been doing a bit of reading on the wiki concerning this

[bss325i]

2.8 needs the block decked to get the squish as per 325 OE setup , so both require a vernier pulley to get the cam timing 100% right.

didint think the 2.7 build needed to get the block decked.. i know theres a few ways of building the 2.7 been doing a bit of reading on the wiki concerning this

I thought it was the 2.8 that didn't need decking?!

[ricey46]

they both do to get them bang on depending on what way you do it

[sterlingsilversport]

sorry if a bit slow, might just have different word for it this side of the water, decking?

[jbh]

skimming the block

[daimlerman]

Block will need 'decking' if you use 325 pistons.I used the heavier eta pistons so did not need to deck the block.Must admit that Ant's post is the first indication that I can remember reading that advises decking for a 2.8 build.But,Ant builds these things for a crust so he knows what he's talking about!

[gooner1]

We are talking aboutskimming the cylinder head block here ,are,nt we?

[stonesie]

Nope the block, block, where the pistons live.

[gudgeon]

(Piston data from Mahle)

325i:
Crank stroke =75mm, 75/2=37.5 (max distance from crank centreline to big end centre)
Conrod = 135mm
Piston compression height = 34.2
Total = 37.5+135+34.2 = 206.7mm

327ETA:
Crank stroke =81mm, 81/2=40.5 (max distance from crank centreline to big end centre)
Conrod = 130mm
Piston compression height = 35.7
Total = 40.5+130+35.7 = 206.2mm (is this block shorter?)

2.7 stroker with 325 pistons:
Total = 40.5+130+34.2 = 204.7mm (2mm decking)

M52 crank = 84mm
Total = 42+130+34.2 = 206.2mm (maybe .5mm decking required, looks to me like ETA pistons wouldn't work here)

[Ant]

just to ad to the above

325 and 320 blocks are 206.0 mm crank CL to deck heght

ETA are 206.5mm, no idea why but thats the quoted dims and they do match up when measured.

[gudgeon]

206.0 ?

I wonder where my extra 0.7 came from? They are pretty crudely calculated figures.

[reggid]

i am almost certain i measured my B25 smack bang on at 206.7mm.

B28 crank, Eta rod, B25 piston nominally lower piston height by 0.5mm

+((84/2)-(75/2)) - (135-130) = 0.5mm

[gudgeon]

Yeah, I think the way you've expressed it is better.
Piston height is not really relevant for relative heights, only for custom/aftermarket piston specification.

My figures for piston height should be taken with a pinch of salt as I don't really know what "compression height" is. There is also dome height, various land heights and other small discrepancies.