Rebuilt M20 Burning Oil- M50 Worth It?

[jtdogblue]

I think my machine shop forgot to mark the valves when reassembling (didn't do new guides)... I got the purple smoke puffing when I lift at high rpm, sooooooo I'm thinking of doing a m50 swap. Problem is, I saw the dyno thread for the m5x's and I've seen some m20 2.7i's with better numbers than theirs.. I'm a little iffy about vanos too..

Somebody convince me to do a 24v swap? or rebuild m20?

Vanos= better torque, drivability, and gas mileage at lower rpm, right?
Non vanos= easier to turbo, less sh*t to break, and aftermarket cams?

Any thoughts on ZF vs g260?

So far my understanding is that the volumetric efficiency of the m50tu is more like 85-95% compared to the m20's 65-75%, so it should get better fuel economy..

I'm guessing around $2000 for a decent swap, vs about $2000 in motor work I want done to my m20...

I'll be doing a lot more searching and adding to this thread, just thought I'd give myself a place to start for now.

Edit: Yummy: http://www.e30dohc.com/wiki/index.ph...HC_Swap_Basics
I'm liking the m52b28 obd1 s50 cam combo.....

Ooohhh I have the 11/86 325e driveshaft, 96mm bcd, looks like the zf should bolt right up.. (with 12mm to 10mm spacers)

[jrdeamicis]

The m52 m3 cam combo is nice. However i love my S50 / S52.
Vanos is not iffy. It has been dealt with an its awesome.


Do not put in anything smaller than a 2.8.
Do not skimp on gaskets
Do not skimp on tune.
Actually do not skimp on anything.

[eoddom]

I'm going through this same struggle right now....m50 or m20b25. I found a full s50 swap that the guy will ship to me for 2500 dollars. Very tempting ATM.

[Killacortes]

The m52 m3 cam combo is nice. However i love my S50 / S52.
Vanos is not iffy. It has been dealt with an its awesome.


Do not put in anything smaller than a 2.8.
Do not skimp on gaskets
Do not skimp on tune.
Actually do not skimp on anything.

Agreed. Regular m50b25 won't do much for ya. Unless you just prefer an m20 then I would say build your m20 up. I've had a m50 and I actually like my m20 better. But I wish I had a s5x :)

[Ceeker]

I can't see the valves not being marked would pose a problem for the guides if the seats were reground and valves were ground - unless, the valve guides were badly worn? Most probably the valve seals were gone and not replaced.

[jtdogblue]

Yea it was a higher mileage head. Valve guides wear unevenly, put the one that was -.001 in a hole thats +.002 and you have a problem. Valve seals were replaced as well.

[scottinAZ]

Given the choice to do it all over again, rebuild M20 or go 24v, I would go 24v again in a heartbeat. More modern engine, better power and torque than M20 (stock). More modern and efficient engine design.

I started with the G260, and now have a ZF. I think the ZF is a better box, just because its newer, remember 99% of the G260's out there have a shitload of miles on them and are starting to show their age. Not all of them have aged gracefully. The ZF I now have came out of a 99 E46 and has less than 100K on it. Plenty of life left, whereas the G260 it replaced had unknown mileage and was worn out (bad bearings).

My personal preferance is to go with newer when available and practical to enhance the longevity of the car.

[AnimalE30]

I love my m50tu over my old m20.

I'm not sure what diff I have, but I'm only geared to 125. The m50tu with m20 flywheel plus shorter gearing is awesome in town and on on-ramps. On the high way it's 20 mpg and a sound that makes me deff (only have a resonator and magniflow lol).

[reelizmpro]

I think nowadays it depends on how much u can do the swap for. If you can diy, and get the m50 cheap, it makes perfect sense. there are plenty of m50s in the junkyards but I don't see it being worth it if you have to pay a shop to do it.

[20gmr]

Smoke when you lift off the throttle is indicitve of bad rings nothing to do with the valves. The high vacuum in the cylinder pulls oil up past the rings. If you look inside with a bore scope you will see the very outside of the piston will be clean all the way around.

[SwiftE30]

I think nowadays it depends on how much u can do the swap for. If you can diy, and get the m50 cheap, it makes perfect sense. there are plenty of m50s in the junkyards but I don't see it being worth it if you have to pay a shop to do it.

^^ a swapped e30 is the bees knees! especially if you can get an s5x over m5x. the obd1 conversion is actually pretty simple if you find an s52.

if you have to pay a shop to do the 24v swap then just stick with your m20 and pay a shop to work on that dinosaur. However, and im sure everyone on r3v will agree, spending the time doing the swap yourself, and gaining all the knowledge, is SOO gratifying and 100% worth it in the end.

s5x swap (yourself) > built m20

[TimKninja]

I love my 24v swap. Much more reliable motor. I feel dumb for ever putting money into my m20 to begin with.

Too bad your on the other side of the country. Id sell you my whole 24v car for 2k.

[328ijunkie]

Smoke when you lift off the throttle is indicitve of bad rings nothing to do with the valves. The high vacuum in the cylinder pulls oil up past the rings. If you look inside with a bore scope you will see the very outside of the piston will be clean all the way around.

no

[SwiftE30]

I love my 24v swap. Much more reliable motor. I feel dumb for ever putting money into my m20 to begin with.

Too bad your on the other side of the country. Id sell you my whole 24v car for 2k.

moving on to a new project or something? 2k for a 24v e30 is crazy!

[TimKninja]

moving on to a new project or something? 2k for a 24v e30 is crazy!

Cars got rust. I want a two door . ;)