2.7L stroker questions

[FlabergastedCod]

So I'm building a 2.7L stroker M20, and the whole pistons/head thing is confusing me. I've had many people tell me conflicting things here and there, I just want a solid answer Lol.

I picked up an 87 ETA motor, so I have the crank, rods, and ETA pistons, ill be buying a 91' parts car here in a bit, and I guess I just don't know exactly what I'm doing. Some people have said to use 325i pistons and head with the block decked 2mm, but others have said that id run into valve clearance issues. Id like to not use custom pistons if I have a choice because any power I make out of this one will be higher than my M10. Any advise on this topic would be great, and no, I won't be doing an M5x swap.

[It's Soda Not Pop]

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

[It's Soda Not Pop]

https://strictlyeta.net/technical/328i/

[digger]

So I'm building a 2.7L stroker M20, and the whole pistons/head thing is confusing me. I've had many people tell me conflicting things here and there, I just want a solid answer Lol.

I picked up an 87 ETA motor, so I have the crank, rods, and ETA pistons, ill be buying a 91' parts car here in a bit, and I guess I just don't know exactly what I'm doing. Some people have said to use 325i pistons and head with the block decked 2mm, but others have said that id run into valve clearance issues. Id like to not use custom pistons if I have a choice because any power I make out of this one will be higher than my M10. Any advise on this topic would be great, and no, I won't be doing an M5x swap.

The best oem based 2.7 is

eta crank
eta rods
m20b25 pistons
Block decked 2mm
885 cylinder head

[ForcedFirebird]

The best oem based 2.7 is

eta crank
eta rods
m20b25 pistons
Block decked 2mm
885 cylinder head

This.

[FlabergastedCod]

This.

thats what ive heard, but numerous people have said id either have terribly low cr or valve clearance issues. ill test-fit everything just to make sure though. Thanks!

[ForcedFirebird]

thats what ive heard, but numerous people have said id either have terribly low cr or valve clearance issues. ill test-fit everything just to make sure though. Thanks!

I've built a bunch of them at work, they put down good power.

The low compression happens if you just slap the 885 on the eta bottom end and call it a day.

I put two of my builds on the dyno, same day, post # 43 https://www.r3vlimited.com/board/for...52#post7038352

[FlabergastedCod]

I've built a bunch of them at work, they put down good power.

The low compression happens if you just slap the 885 on the eta bottom end and call it a day.

I put two of my builds on the dyno, same day, post # 43 https://www.r3vlimited.com/board/for...52#post7038352

alright, cool, and would I be able to fit something like a 272 or a 284/280 cam in? Any cam recommendations? I'm building the car for time attack

[ForcedFirebird]

Read the post, the specs are there for both engines.

[digger]

I think what he is trying to say is go easy on the cam duration and stock is not a bad thing when you’re only mildly modified. An Alpina cam would be a good think but unfortunately nobody got one copied so chances finding are low.

[hasa]

I have a gut feeling that there was something other thing wrong than just the 272 cam producing 20hp less. But there is no way to prove the claim.

[digger]

I have a gut feeling that there was something other thing wrong than just the 272 cam producing 20hp less. But there is no way to prove the claim.

I agree there are a number of tangible differences that could explain the difference e.g stock ecu, no headers, a bit less squish, stock intake

As the OP is going to do track build then a 272 cam would likely out perform the stock cam at top end all else equal Any more duration than that needs supporting mods to cylinder head, intake manifold and static compression ratio imo

[ForcedFirebird]

I have a gut feeling that there was something other thing wrong than just the 272 cam producing 20hp less. But there is no way to prove the claim.

The diff was smoked. Didn't hear it on the dyno, but when we were pushing the car out of the trailer, the car wouldn't move forward easily, only back and was making an awful noise (pinon bearing was trashed). For what it's worth, the 272 car lapped almost a sec faster at Daytona after the dyno session and we replaced the diff. I actually drove it and I was able to hit the rev limiter (7200rpm) in 5th just before the start/finish line - didn't GPS, but with 205/50 tires, that should be about 143mph. With a stock engine, we would hit an aero wall at about 5500-6000rpm in 5th unless there was a draft (~120mph-ish).