Differences between e30 and e28 m20b27 blocks?

[Dawskip]

Wanted to use my spare block from my e28 for my e30s the I build (885 head), I noticed the crank Pulley isn’t toothed like my e30s block, does that matter at all? Can I use my cps that I use on my toothed-block?

[ForcedFirebird]

If you have a 2.5 in your e30, the 2.7 bottom end is a "downgrade". You will lose about 20whp over a plain old m20b25.

Compare post #5 and #11 in my dyno thread:

https://www.r3vlimited.com/board/forum/e30-technical-forums/engine-drivetrain/m20/378740-forcedfirebird-s-m20-dyno-thread#post9875136

[ForcedFirebird]

Here is a good read for 'ya:

https://www.r3vlimited.com/board/forum/e30-technical-forums/engine-drivetrain/m20/64366-1-3-motronic-up-grade-2-7i-how-to

All your questions will be answered there. ;)

[Dawskip]

If you have a 2.5 in your e30, the 2.7 bottom end is a "downgrade". You will lose about 20whp over a plain old m20b25.

Compare post #5 and #11 in my dyno thread:

https://www.r3vlimited.com/board/for...ad#post9875136

It’s for a turbo build, wanted the lower compression.

[ZeKahr]

Wanted to use my spare block from my e28 for my e30s the I build (885 head), I noticed the crank Pulley isn’t toothed like my e30s block, does that matter at all? Can I use my cps that I use on my toothed-block?

Your E30 might be a Super ETA (1988 only). Those use Motronic 1.1, which mounts a single crank position sensor in the front of the engine to read pulses off a toothed crank pulley. You E28 is most likely a 1987 or earlier Eta with the Motronic 1.0. These cars mount the crank position sensors at the back of the gearbox. You should be able to reuse the CPS. The Eta blocks from an E28 and E30 shouldn’t be any different from one another.

[Dawskip]

Your E30 might be a Super ETA (1988 only). Those use Motronic 1.1, which mounts a single crank position sensor in the front of the engine to read pulses off a toothed crank pulley. You E28 is most likely a 1987 or earlier Eta with the Motronic 1.0. These cars mount the crank position sensors at the back of the gearbox. You should be able to reuse the CPS. The Eta blocks from an E28 and E30 shouldn’t be any different from one another.

My plan is to jsut take my toothed pulley and put it on the eta block, and use the cps from bmw b25.

[ForcedFirebird]

It’s for a turbo build, wanted the lower compression.

You will still have less power then a b25. Think about it - if you start with 155whp and add 1 bar, you theoretically should be about 300whp. If you start with 130whp and add a bar, then you will be closer to 260whp with the same exact turbo kit and boost levels. I would rather take the extra 40whp than be able to say "I have a stroker".

Also, the stock m20b25 is 8.8:1 and the 885 head on a 2.7 is 8.4:1, neither are "high compression" in regards to a turbo build, and I have had no fear sticking turbos on m50's here at work (10.5:1) over the years - there's one in the parking lot now, even.

You can do as you like, but the 2.7 with 885 head is an upgrade ONLY if you started with an eta car (just swap the head to go from 120whp to 130), or if you have an '88 seta which uses the crowned pistons like the b25 does.

[ForcedFirebird]

My plan is to jsut take my toothed pulley and put it on the eta block, and use the cps from bmw b25.

You need all the sensors, AFM, intake manifold, throttle body etc. It's all in that link.

After more posts, realized you may both m20b27's, in which an 885 head is an upgrade over the 200 casting. In that case, there's no difference from the <1988 e30 or e28 m20s, with the excpeption some of the early e28 blocks have a giant freeze plug on the back, inside the trans bell housing.