M20 Stroking options

[ryan_george]

Hey guys. As of today I am the new owner of an 87 325i. I also have an 86 325e that I have been driving for about 2 years. I am very interested in stroking the "i" motor, and have done quite a bit of research into it. I have searched here, bimmerForums, mod_m20, etc. However, I am hearing conflicting stories from people who have not done the conversion themselves. I would like to keeps costs minimal (being a student), so that means I don't want to spend $1000+ CAD on new pistons. I've heard of using super eta pistons (rare-ish), using euro eta pistons (super rare), and even using 325i pistons but having the top shaved. There is also the option of shaving the head and/or block.
Has anyone built a stroker using the aforementioned methods? Or does anybody with expereince in m20 rebuilding have any suggestions? I plan to rebuild the engine over the winter and continue to drive the 325e to work.

Thanks for your help.
-Ryan

[AdamF 88iS]

One of my customers recently built a stroker by putting an I head onto an E block and shaving the head and block quite a bit to get the compression back up because the I combustion chambers are bigger.

[nando]

won't that fuck up the cam timing?

[Rigmaster]

Re: M20 Stroking options

There is 1 simple option, that can use all BMW parts, no $$$$$ custom stuff and no $$$$$ custom machine work.

Use a Super eta ('88 ONLY 325 or 528e) engine- if your 325i is running well, just put the top end from that car on the super eta bottom end- use the whole thing from your 325i, the intake, injection, head, etc, etc. Almost like magic, you now have a 2.7i M20!

You can do all sorts of other things to improve performance- custom ECU chip, etc, but this is the easiest method to get the 2.7l displacement with an "i" motor.

Bret

Hey guys. As of today I am the new owner of an 87 325i. I also have an 86 325e that I have been driving for about 2 years. I am very interested in stroking the "i" motor, and have done quite a bit of research into it. I have searched here, bimmerForums, mod_m20, etc. However, I am hearing conflicting stories from people who have not done the conversion themselves. I would like to keeps costs minimal (being a student), so that means I don't want to spend $1000+ CAD on new pistons. I've heard of using super eta pistons (rare-ish), using euro eta pistons (super rare), and even using 325i pistons but having the top shaved. There is also the option of shaving the head and/or block.
Has anyone built a stroker using the aforementioned methods? Or does anybody with expereince in m20 rebuilding have any suggestions? I plan to rebuild the engine over the winter and continue to drive the 325e to work.

Thanks for your help.
-Ryan

[ryan_george]

Re: M20 Stroking options

There is 1 simple option, that can use all BMW parts, no $$$$$ custom stuff and no $$$$$ custom machine work.

Use a Super eta ('88 ONLY 325 or 528e) engine- if your 325i is running well, just put the top end from that car on the super eta bottom end- use the whole thing from your 325i, the intake, injection, head, etc, etc. Almost like magic, you now have a 2.7i M20!

You can do all sorts of other things to improve performance- custom ECU chip, etc, but this is the easiest method to get the 2.7l displacement with an "i" motor.

Bret

Which is pretty much the same as just finding the super eta pistons, regular eta crank, and throwing it into the 325i.
I guess that's probably the cheapest route to take. I might even be able to shave the head for a bit more compression.
I live in Canada, and I dont think that super eta's were sold here. Is there any reliable and cheap place in the states to have a look at for the pistons?

[rs4pro3]

Pick up the October Total BMW magazine. It has a good article on the different ways to build a stroker m20.

[ryan_george]

Pick up the October Total BMW magazine. It has a good article on the different ways to build a stroker m20.

Yeah I've already got that. However, the pistons they talk about using are Euro Eta pistons, different from anything we've got.

[Rigmaster]

Re: M20 Stroking options

I live in Canada, and I dont think that super eta's were sold here. Is there any reliable and cheap place in the states to have a look at for the pistons?

Hmm, I'm 99.9% sure that if you can find a 1988 325 or 528e in canada, it will be the "super eta". BMW never marketed the '88 as a "super eta", it's just sort of an in-between version...part 325e and part 325i. You are correct about being able to use the super eta pistons + eta crank, but you would probably have better luck with the complete engine, or at least the complete "matched" bottom end.


You should be able to find a used complete super eta engine for ~$500 or less. I sold one to a guy in Canada about a year ago- shipped it to him on a truck.

Bret.

[ryan_george]

Re: M20 Stroking options

Hmm, I'm 99.9% sure that if you can find a 1988 325 or 528e in canada, it will be the "super eta". BMW never marketed the '88 as a "super eta", it's just sort of an in-between version...part 325e and part 325i ...

I have a friend who owns an 88 325, and it is not a super eta. And I just bought this 325i mainly for the engine, so buying another engine is out of the question. But thanks for the input anyhow.

[ryan_george]

Well I sourced out some early euro eta pistons, hopefully I'll be able to get them.
I'll try and keep you guys updated on the progress.

[ColdAccord]

euro eta pistons are tough, ask rs4pro3. he had 3 sets i believe. one set was the wrong kind, and the rest were lost in shipping

I looking for the euro pistons for so long. couldn't get em. and the super eta pistons produce too low of a compression ratio, it's like 8.1:1.

I ended up getting pistons from racing dynamics. 10.2:1 compression ratio, and use 325i rods. should be in the 230hp 230 torque range with the other stuff I've got. ive gotta wait until my winter car is on the road to do the swap, so we'll see how it goes

[ryan_george]

euro eta pistons are tough, ask rs4pro3. he had 3 sets i believe. one set was the wrong kind, and the rest were lost in shipping

I looking for the euro pistons for so long. couldn't get em. and the super eta pistons produce too low of a compression ratio, it's like 8.1:1. ...

Ya, I've done a bit of talking with rs4pro3 about the pistons. He thinks they'll work nicely. I've found someone overseas who can get me some :o

[AdamF 88iS]

won't that fuck up the cam timing?

Yea. You have to adjust it about a half tooth, which of course fucks with the dist timing, but it runs well in the end.

[Sean]

euro eta pistons are tough, ask rs4pro3. he had 3 sets i believe. one set was the wrong kind, and the rest were lost in shipping

I looking for the euro pistons for so long. couldn't get em. and the super eta pistons produce too low of a compression ratio, it's like 8.1:1.

I ended up getting pistons from racing dynamics. 10.2:1 compression ratio, and use 325i rods. should be in the 230hp 230 torque range with the other stuff I've got. ive gotta wait until my winter car is on the road to do the swap, so we'll see how it goes

Wouldn't shaving the head a little bit bring that ratio up more? Cause, I have everything I need (a Super Eta engine and an I engine) and will be doing this very soon.

[ryan_george]

euro eta pistons are tough, ask rs4pro3. he had 3 sets i believe. one set was the wrong kind, and the rest were lost in shipping

I looking for the euro pistons for so long. couldn't get em. and the super eta pistons produce too low of a compression ratio, it's like 8.1:1.

I ended up getting pistons from racing dynamics. 10.2:1 compression ratio, and use 325i rods. should be in the 230hp 230 torque range with the other stuff I've got. ive gotta wait until my winter car is on the road to do the swap, so we'll see how it goes

Wouldn't shaving the head a little bit bring that ratio up more? Cause, I have everything I need (a Super Eta engine and an I engine) and will be doing this very soon.

I'm sure everything would work out. Not sure how much to shave though.