M20B20 stroked to 2.5

[petone 0]

I'm looking for some info on the various parts for the M20 engines. I have a 2.5 block (incl pistons, conrods, crank) but no head, manifolds etc. I also have a dead M20B20, which i want to use for the head, manifold etc. effectivly this would be a stroked 2.0 litre rather than a full on 2.5 Unless i came across a whole lot of 2.5 parts cheap as then I am stuck with the 2 bits.

Questions, will the 2.0 litre head work with the 2.5 crank rods and pistons? Will there be any other problems? Will a jetronic loom and ecu be able to handle the extra cc or is a motronic 2.5 must have? Compression ratio? If anyone can help me out or point me to a place or person that can it would be awesome. I wasn't able to find much using searches.

I know that i should be using 325 parts as they are bigger better etc but this is more of a project that i want to do. Also for what i paid for these parts theres no reason not to try it.

Any ideas or suggestions would be awesome.

Cheers guys.

[Gus 5]

the 2 Litre head will work.......but it wont flow enough and your performance will be stunted

having said that its do able and i imagine would be torquey as down low

i would imagine that you would have to use motronic and the loom from that...i dont see l jet working with it without a ridiculous amount of work....however im sure it can be done, but why not just tear it all out and put a system guaranteed to work in, without having to muck around.

interesting little project, take pics!

[Guest Andrew]

I'm fairly sure the pistons will hit the head without modification. It will also be gutless - but heaps of torque. The 320 had a big port and small port head (even the big one has smaller exhaust ports than a 325 head) - so try find a big port head.

L-Jet should work.

But why? Just get a 325 motor and put that in.

[petone 0]

I'm fairly sure the pistons will hit the head without modification. It will also be gutless - but heaps of torque. The 320 had a big port and small port head (even the big one has smaller exhaust ports than a 325 head) - so try find a big port head.

L-Jet should work.

But why? Just get a 325 motor and put that in.

I already have the 2.0 complete but its dead, i haven't taken the head off so i don't know what ports it has. I was worried about the smaller head not being able to flow enough but that said, in the article on the 2.7 build gus posted they say the 2.0 head flows enough for 200 hp. In they same article they also say the 2.5 pistons will hit the 2.0 head, but that is for the longer stroke so i might be alright with the shorter stroke of the 2.5 As for why... complete 2.5 engine is a little out of my budget, and i just want to play with an engine.

[petone 0]

Just had another thought, i may be able to use the smaller conrods from the 2.0, which are 5mm shorter, although this may drop the compression too much. Anybody got links to some good tech sites?

[gmccormack 0]

But why? Just get a 325 motor and put that in.

Exactly Andrew. Why bother building an engine out of mismatched parts. A 325 or 525 wreck will only cost around $1000 and you end up with plenty of spares

[BM WORLD 1286]

But why? Just get a 325 motor and put that in.

Exactly Andrew. Why bother building an engine out of mismatched parts. A 325 or 525 wreck will only cost around $1000 and you end up with plenty of spares

i agree . just pick up an old 525e e28 2.7L and stick your 2l head or pick up a 323i head (appartly thats the best flowing head) or 2.5l head . 323i runs l-jetronic

[Guest Andrew]

But why? Just get a 325 motor and put that in.

Exactly Andrew. Why bother building an engine out of mismatched parts. A 325 or 525 wreck will only cost around $1000 and you end up with plenty of spares

i agree . just pick up an old 525e e28 2.7L and stick your 2l head or pick up a 323i head (appartly thats the best flowing head) or 2.5l head . 323i runs l-jetronic

I have my 2.3 head running on motronic with the rest of the 2.5 motor.. the top of the head had to be machined for the ridges that stick up on 325 pistons.

[CaM 0]

word, I reckon just get a 325i engine, or a crashed/rusty 325i car

for the money it seems you will have to spend to get a wreck, you'll have to spend that on headbolts, gasket kit, blah blah blah, then you have to get a loom and ecu from a motronic, and get it all sorted and hooked up if you can't do it yourself.... plus find a gearbox, relevant crossmembers and driveshafts if required, bigger radiator (i imagine),6cyl tacho dash and all the little other bits and pieces you never really think about that a donor car supplies at no real cost, all the while selling bits you dont need to fund a small part of it...

[petone 0]

I get what your all saying about just buying a f*#ked 325 and i know it would be the simplest and easiest (and maybe cheaper) by a long shot. I was just seeing if i can do anything with these random bits of engine. As cam said, i need to work out what other bits i need and what they'll cost me vs cost of 325 wreck

Ok, lets just say that this engine will be going into 4wd or something.

will 2.5 pistons and crank work with 2.0 head and conrods? (If so any idea on c/r?)

Or can someone tell me where/how i might find out.

Please no more on buying a 325

[CaM 0]

try on the dtmpower.net forums ..... they have a shitload of users, so that would, if anywhere, get you underway....

gotta probably factor in for new mains, bigends, gudgeons, blah blah blah, let alone any machining (lineboring mains, rebore cylinders balh blah blah).... so yeah, at least you're going a decent way about it...

I think brent has a 2.7 sitting up there maybe? that + your parts would probably build up something decent, and you'd be able to play with that 2 litre head to get it flowing - perhaps a winters night project - die grinder in front of the fire :mosh:

[gmccormack 0]

Just had another thought, i may be able to use the smaller conrods from the 2.0, which are 5mm shorter

I don't think so. The piston skirts will slam into the crank on the down stroke

[petone 0]

dam. cheers anyway guys.