m20 2.7i vs m50 non vanos 2.5i

[napabavarian]

Siting in my front yard is a 1991 325i with a perfectly good engine, but it needs a new transmission...mostly because I can't drive an auto! so I'll need to change the engine anyway, right? good excuse...

The choice of these 2 engines is simple, I have a good Super eta with a 5 speed bolted to it and spare I head, as well as a spare m50, either way I'd get reground cams and a chip to spice things up a bit :twisted: got a 3.73 LSD yesterday :mrgreen:

Are there any advantages/disadvantages of either swap? I figured it would be an easy choice of the m50, but some people seem to like the m20 better.

[Mike]

timing belts or die

[napabavarian]

Ah well, I have plenty of those, 3 m20b25 and an m20b27 :D but project creep = dollars, I might need to but a driveshaft, realistically I could drop the I head on the S-eta bottom end with a 5 speed already bolted to it and call it a $90 head gasket set :) But then I'd get a reground cam, chip, upgraded head gasket, and I'm sure I'd find more to do :(

[Ray Smoodiver]

A non vanos 2.5 was pulling away from my alpina 2.7 above 80mph

[Jon325i]

There are advantages to each:

2.7 M20 = pretty much plug-n-play swap to get it going. Better torque down low which makes passing w/o shifting possible. Being in Calif, it should look visually identical to the M20B25 in your car now so you can probably get away with not having to deal with the state referee (which you will have to visit and get approved if you go the twin cam route).

NV M50 = I see these as essentially an M20 with one more cam, 12 more valves and a timing chain vs. a timing belt. They do have more pull at the higher revs which is nice. A bit more involved to get it installed but since so many of these have been done getting the right bits to make it work shouldn't prove to be difficult.

I guess you just need to evaluate which 'gain' best suits your driving style: more easily had low end torque (2.7) or better mid-range and top end grunt (M50).

Jon

[ditchdigger]

I was actually going to ask this same question. I have SETA psitons in a box, an ETA bottom end on the stand and a complete "i" motor in the car. I was also just offered a non-vanos M50 for a good price.

Cant really decide which way to go myself.

[Ray McCooney]

Hydraulic lifters, timing chain, fuel economy, smoother power delivery.........

[Kilomph]

Umm, you ARE going to a 5 speed, right?

I'd say M50 just for ease of maintenance, I'm getting tired of dealing with all the M20s belts and valve adjustments. I'll keep mine running as long as I can, then toss in an S50.

[napabavarian]

Umm, you ARE going to a 5 speed, right?

Yes, the only auto I can stand is the 5 speed Allison behind my duramax


On a side note, anyone want to buy a 4 speed automatic from a 1991 325i? Drives great arround the yard :D but car isn't registered, the light front damage poked a hole somewhere in the cooling system :(

[napabavarian]

Wait...

I just realized...

It isn't the happy dance...



it's Rodney King!

[E30_pilot]

swap the m50 into the '91 and go get it registered.

[416stroker]

I was runnning a 2.7i in my 87 but now I went to a non-vanos m50. when my dme gets here I can give you a comparison bye next week hopefully. I hung with a new gt mustang with my m20 I never fell past his front fender.

[nando]

your typical kludged together 2.7i isn't going to be very spectacular - unless you want to build a serious motor, I'd look for an M52. screw the M50NV..

[digger]

your typical kludged together 2.7i isn't going to be very spectacular - unless you want to build a serious motor, I'd look for an M52. screw the M50NV..

+1

the last thing you want to do is swap in an engine and not get any extra CC. An M20 stroker needs good compression, mild cam, good exhaust and tuning to bring any sort of worthwhile performance gain over a m20b25.

[rThor432]

screw the M50NV..

Plus one.