Need help with building a stroker for my m20b25

[dillanmac3]

Im trying to find all the parts and find the right setup but cant seem to find what i need. I need to know what a good setup would be for my motor, i want to make a 2.7 or 2.8 but i dont want to buy those expensive kits. So can someone please tell me what kind of pistons, crank, and all those things i need.

[march109]

This is open to some debate but the easiest and cheapest ways IMO are;

2.7l:
Buy a 525e (2.7l eta motor), and add the head from a m20b25. Obviosly the eta motor was only supplied in auto to the uk so you will then have to convert it to a manual transmission.

2.8l:
M20b25 block, head and pistons, m20b20 (130mm) rods and crank from a m52b28 with spacer made up from specs in the wiki.

2.8 is obviosly more spannering but good eta engines are like hens teeth now, these are the easiest not best methods too!!

[daimlerman]

Depends on what you are starting with as well.
If your base is a 325i motor,'all' you need for a 2.8 is crank,'rods and a spacer for the front of the crank.Have a read through 'stonsies' thread.
If your base is a 320i,using the '731' head from this straight onto the 525e short motor is the cheapest way....remember that E28 525e went out of production in '87 and the remaining one's are high milers so rings and a crank regrind will gobble budget.
In general,whichever route you choose,to get the best from your hard work you will need to completely re-build the engine,expect to shell out at least £1500 for a DiY based build....

[dillanmac3]

yes im starting with a 325i motor. What type of crank, rods, and a spacer will i need? from a 2.7 motor?

[stonesie]

If you are building a 2.7 then you will need the 2.7 crank and the 2.0 rod's with the 2.5 pistons and probably some metal machined off the 2.5 block to bring the compression ratio back up.... Unless your going with a turbo too


If you are building a 2.8 then you will need the spacer because the crank will be from the later 24 valve 2.8 which used a cam chain instead of a belt so it has nowhere for the oil seal to seal, you will still need the 2.0 rods and 2.5 pistons but you might have to have the piston skirts machined down a bit to clear the crank ballance weights, the machining of the block is optional on these builds as they give roughly 9.3:1 compression which is just a smidge less than the early version of the 2.5 (9.4:1) but more than the later version (8.8:1).


My own is a 2.8 but I have had a little skimmed off the block top to bring the pistons to the standard height in the block relative to the head.... I think i could have cobbled together a 2.8 for around the £1500 budget but i got carried away with shiney things like a catcam and vernier pully

[Simon13]

read the sticky about building a 2.7 its in this section of the forum! it tells you virtually everyway of how to build a 2.7 as there are many ways to suit various budgets