Lets start this of with, yes I should/could start out with the B25, etc. This is more of "has it been done and how did go?" sort of thread.
So as I was saying before. has anyone done it?
I know the bore size on the B20 is 4mm smaller than than the B24 and B25, so swapping pistons from a m54b30 are a no (unless you over bore the block). But what about the rods and crank?
Edit: upon further investigation across the web I could use the rods and piston from a M54b22 (correct me if I'm wrong) and the M54b30 crank?
Last edited by Tapanui; 01-12-2019 at 04:33 AM.
A bore and hot tank isnt expensive at all. See if indeed you can bore the block out to fit 84mm pistons. I can almost garuntee the 2l pistons wont work with a b30 crank as even 2.5l pistons wont work.
Nobody would recertify these machines after somebody screwed with them without any visibility into what they did.
HONK! HONK! Clown car coming through!
-Oakdizzle
Don't know about the m54 crank, but I've seen a few 2.6 stroker builds.
They use the m52b28 or m51d25 crank (compression with the m52 crank is off, supposedly the diesel crank gets you around the stock 10.5)
If you have a non-vanos b20 you can use stock conrods (135mm), but you'll need the vanos pistons.
Vanos needs 135mm conrods with stock pistons.
From what I've read you can safely bore to 84mm if you're staying n/a, but keep in mind you'll still have the restrictive 80mm b20 head and I'm fairly sure the b25 head doesn't match the water passages on the b20 block.
Now, don't quote me on this because it's been a while since I read into this
I can see if I can find the threads again (most of them were russian)
Before you start buying parts, make a realistic cost estimation, including all gaskets, new head bolts, etc. Chances are that just transplanting an M52B28 (also grab the exhaust) will be way more cost-effective and less work. Don't know what the engines cost in Australia.
It's interesting though, and it has been done before.
1997 E36 BMW 323i (European) 275k km (171k miles), with following small mods:
- Chip tuned DME (190HP/257Nm); 328i dual pipe exhaust (plug&play); Meyle HD control arms, Bilstein B4 shocks
- Fan delete mod: Stock 92C thermostat, 80/88C temp. switch, 80/20% water/coolant; INPA says temps 100% OK
- Throttle body coolant hose delete mod; Comprehensive ASC Delete option list; Solved: -30 additive adaptation values
Its not just about wrist pin location, it also has skirt length in relation. For instance b30 pistons will have the same wrist pin center to the piston top as b25. But tub25 have a longer skirt and rod so when used on a b30 crank with b30 shorter rods, the rod will hit the piston skirt in rotation and wont allow the engine to rotate. Essentially you cant use b25 pistons or rods on a b30 setup unless its a 2.8l with bored over with oversized pistons.
Nobody would recertify these machines after somebody screwed with them without any visibility into what they did.
HONK! HONK! Clown car coming through!
-Oakdizzle
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