2.5 to 2.7i

[yberther]

Hey I've read through all the threads and posts about making the 2.7i. I'm planning on making one, but I was wondering if it would just be easier to start off with an i engine, tear it down, replace the crank with the eta and just run it like that.

Will there be interference with the larger stroke and the head if I run the e rods on the i pistons? or the seta pistons?

I'm hopefully starting my build in 2 weeks so I'm trying to figure out the cheapest way to build the 2.7i

[yberther]

can someone please help me??

[Miasma]

Hey I've read through all the threads and posts about making the 2.7i.

Really trying not to be rude but this HAS been covered alot and if you had read all the thread's you would have your awnser. ;)

[ban1]

x2

[yberther]

ahh touche the 81mm and 75mm difference would create an interference. Sooo the eta bottom end is necessary.

[Miasma]

Im fairly certain the only difference to the 2 block's are bore. I may be wrong.

[kenika65]

um to my understanding the 2.5 and 2.7 M20 block is identical so it doesn't matter if you swap parts they are identical.

[Miasma]

um to my understanding the 2.5 and 2.7 M20 block is identical so it doesn't matter if you swap parts they are identical.

I belive other than the bore yes.

[yberther]

actually...I'm pretty sure the bore is the same...

from wikipedia :
2.7:The 2.7 L M20B27 was designed for efficiency (thus the e for the Greek letter eta in 325e). It had an 84 mm (3.3 in) bore and a longer 81 mm (3.2 in) stroke for a total displacement of 2693 cc.
2.5: It featured "885" head with larger ports and valves, 84 mm (3.3 in) bore, and 75 mm (3 in) stroke.

I just wasn't sure if the larger stroke would cause interference with the head.

[Miasma]

My mistake.

M20B25:

1987-1991 325i/is/ix/ic (1992 for cabrio)
inline 6 w/ monotronic 1.3(after 89) or 1.1 ecu, SOHC belt driven
12 valves two per cyl., multiport fuel injection

head casting number: 1-705-885 spanish casting "AMC"

displacment: 2.5l, 2494cc

power: 168hp @ 5800rpms 164lbs tq @4300rpms/ 171hp noncat version

redline: 6200 rpms

weight: 175kg

comprestion ratio: 8.8:1 (US 87-90) 9.7:1 (euro spec 85-89)

idle speed: 760 +/- 40 rpms

Piston comp height: 34.2 mm / 1.346 in

firing order: 1-5-3-6-2-4

intake valve size: 42mm

exhaust vavle size: 36mm

valve clearance: .30mm/.012" cold .25mm/.01" hot

valve seat angle: 45 degrees

bore and stroke: 3.31" x 2.95"

rod length: 135mm

piston bore: .858"

Piston dish: 6.2mm

cam duration: 256 deg

valve lift: 10.1mm

cam LCA: 108 deg

cam bearings: 7

cam end play: .008"

cam duration: 256 degrees

oil presure @ idle: 18psi

intake runner length: 360mm

Throttle body inlet: 65mm

throtle body butterfly: 60mm

Throttle body outlet: 63mm





M20B27:
1984-1988 325/e/es
SOHC 12 valve two valves/ cyl. Inline 6 Cylinder BOSCH Motronic 1.0(84-87) Motronic 1.1 (88)
super eta introduced for one year in 1988

head casting number: 1-705-200 and 1-705-885 (super eta '88 only see notes)

displacement: 2.7l 2693cc

HP:122 @ 4250 / 127 @ 4800 (super eta)

TQ: 170 @ 3200

idle speed: 700 +/- 50

red line: 4750rpms

firing order: 1 - 5 - 3 - 6 - 2 - 4

Bore: 84 mm / 3.311 in
Stroke: 81 mm / 3.189 in

Compression ratio: 9.0:1 (82-87), 8.5:1 (super ETA 87-88)

Rod length: 130 mm / 5.118 in

Rod big end bore: 45 mm / 1.772 in

Crank rod journal: 21.8 mm / .858 in

Piston comp height: 35.7 mm / 1.406 in (82-87), 36.2 mm / 1.425 in (super ETA 87-88)

Piston Dome/Dish: 3.5mm

Int valve dia: 40mm

Ex valve dia: 34mm

valve clearance: .30mm cold/ .25mm hot

Cam shaft duration: 236 deg (belt driven)

valve lift: 9.1mm

cam LCA: 102 deg

cam bearings: 4

intake runner length: 550mm

throttle body inlet: 55mm

Throttle body butterfly: 48mm

Throttle body outlet: 54mm



Notes: Single valve springs, and 1 mm smaller valves prevent this motor from reving past 4500 rpm stock. This motor was intended for fuel economy. It is also known as the "eta". The "super eta" motor, has the same size valves and the same singal valve springs, but it has the same mild camshaft as the non super eta motor. Cast crank, still quite durable for higher than the designed rev limit. same head casting as the m20b25 but with only 4 oil jornals drilled instead of the 7.

All taken from E30tech.

[yberther]

so you can use an i block for the 2.7i...

[kenika65]

LMFAO for the last time all M20 blocks are IDENTICAL, it is only the internals and the head that change unlike the ix M20 which does have a different block but will still take any oem internals

[yberther]

My deepest apologies for my nubness...

[SpecM]

-Holy crap...

-All m20 blocks have 84mm bores. Etas just have a longer stroke, 81mm vs 75mm
-s-etas have the SAME head as a 2.5. The valves are the same, and the cam/valvesprings are an easy swap-in.

[e30wheelman]

i am almost done with this build, and as stated above the blocks are exactly the same. if you use the I pistons then your going to have to shave them. the skirts dont allow clearence for the rods, however if you use Seta pistons with Seta rods every thing SHOULD bolt in fine. yes it is easyer to start with a 325i mostly because all the things like sensors, harness, are already there, but if your talking about just a engine, it was easyer for me to just get a Seta short block and a 325i head. and bolt them together. then i bought a parts car that had been wrecked for 300 bucks and got every thing else i needed.

what kind of e30 do you have?