1.3 Motronic Up-Grade & 2.7i How To

[Swanny]

So do you happen to know what the CR using 325i pistons without decking the block is then? Is it almost stock like 8.75:1 or still above 9:1?

I'd really like to get as close to 10 as possible... sounds like if I don't want to do any machining I should swap my 885 head directly onto the ETA block and not swap pistons and try to find a thin head gasket. This appears to give me a 9.4:1 and with the higher displacement and without machining or bottom end disassembly.

Or I could try to find a set of early 325i pistons which without decking the block looks like it would get me to around 10:1. But they then need machining... and I also really don't want to drop a grand on custom forged pistons.

Or are there any stock 132mm conrods? Haha that'd be too easy.

If my donor car is a 1986 I wonder if there is any chance its an early high compression ratio one... that would be super lucky.

http://www.r3vlimited.com/board/showthread.php?t=193894 is another good thread for piston rod crank combos

[LovelessAndroid]

So do you happen to know what the CR using 325i pistons without decking the block is then? Is it almost stock like 8.75:1 or still above 9:1?

I'd really like to get as close to 10 as possible... sounds like if I don't want to do any machining I should swap my 885 head directly onto the ETA block and not swap pistons and try to find a thin head gasket. This appears to give me a 9.4:1 and with the higher displacement and without machining or bottom end disassembly.

Or I could try to find a set of early 325i pistons which without decking the block looks like it would get me to around 10:1. But they then need machining... and I also really don't want to drop a grand on custom forged pistons.

Or are there any stock 132mm conrods? Haha that'd be too easy.

If my donor car is a 1986 I wonder if there is any chance its an early high compression ratio one... that would be super lucky.

[Bulldog]

Cp101

Ok....I made it to page 12....so I'm just going to ask....what I got is a 87 325e chassis just dropped in a 88 m20b25 with harness....getting spark and fuel pressure....but injectors won't open....everything checks out ....but what about cp101 plug is there any pins that need swapped around ?

[Swanny]

Correct that would be with decking

[LovelessAndroid]

Holy crap, thanks! So much good information I needed.

I think the only thing that I am missing from that is if I need to deck the block the ~2mm he suggests in order to get the CR he talks about. He doesn't follow up on how decking the block changes the CR before and after it appears.

I have a 1990 325i and a 1986 325e I am mating together so it sounds like I'll be at 9.5:1 CR using 325i pistons which is great... unless it decking the block is required and I really don't want to deal with that.

[Swanny]

Hi, guys.

So my car already has a late-model M20B25 and I am going to be getting a cheap B27 engine in the next week. My plan is to make a very cheap 2.7i stroker, and I believe I can do so because I have the B25 already. For current engine mods on the B25, I have upgraded injectors and a Conforti chip but I plan to go to MSPNP so I can do a new intake and tune for my eventual longtube header install. This will allow me to take advantage of the new displacement and CR as well. (And okay, so I am not counting the MSPNP as part of the cost of the stroker build since I was going to do it anyways...) A big part of why I am doing this project is because I have never done and engine build before and I don't want to sink a bunch of money or machining into the first time. I realize that in a lot of cases it is not worth it.

So here is a question that I genuinely CANNOT find the answer to, and I have read a lot of threads from 2007 onwards to see if I could.

What if I use the ETA block, crank, and rods, BUT use the B25 pistons and 885 head? I know this puts my compression dangerously high from what I have read, but how high? And can I just throw on a thicker head gasket to lower it? How thick? Would that thickness be too much for a non-adjustable cam? I have read on strictly ETA that 325i pistons require 2-3mm of shaving but does that translate to adding 2-3mm of head gasket?

I know that typically this swap would require me to have the pistons shaved to get down to 10:1 or 9.5:1 CR or get custom pistons made. However head gasket sounds the cheapest so I was curious. I have access to 93 octane fuel so a higher CR with my MSPNP sounds fun anyways.

Thank you!

http://www.e30zone.net/e30zonewiki/index.php/Building_a_2.7

Does a good breakdown of rod/piston comparisons.

[LovelessAndroid]

Question about using 325i pistons, eta crank and rods

Hi, guys.

So my car already has a late-model M20B25 and I am going to be getting a cheap B27 engine in the next week. My plan is to make a very cheap 2.7i stroker, and I believe I can do so because I have the B25 already. For current engine mods on the B25, I have upgraded injectors and a Conforti chip but I plan to go to MSPNP so I can do a new intake and tune for my eventual longtube header install. This will allow me to take advantage of the new displacement and CR as well. (And okay, so I am not counting the MSPNP as part of the cost of the stroker build since I was going to do it anyways...) A big part of why I am doing this project is because I have never done and engine build before and I don't want to sink a bunch of money or machining into the first time. I realize that in a lot of cases it is not worth it.

So here is a question that I genuinely CANNOT find the answer to, and I have read a lot of threads from 2007 onwards to see if I could.

What if I use the ETA block, crank, and rods, BUT use the B25 pistons and 885 head? I know this puts my compression dangerously high from what I have read, but how high? And can I just throw on a thicker head gasket to lower it? How thick? Would that thickness be too much for a non-adjustable cam? I have read on strictly ETA that 325i pistons require 2-3mm of shaving but does that translate to adding 2-3mm of head gasket?

I know that typically this swap would require me to have the pistons shaved to get down to 10:1 or 9.5:1 CR or get custom pistons made. However head gasket sounds the cheapest so I was curious. I have access to 93 octane fuel so a higher CR with my MSPNP sounds fun anyways.

Thank you!

[franan]

Thank you Swanny I give up. I do not want to deal with piston.

[Swanny]

The first post sums up everything rather well. http://www.strictlyeta.net/technical/328i_1.html this is another good resource. Read up, crack into it, ask questions when you hit road blocks. Good luck!

[franan]

My car is a 1986 325es, I've been reading a lot of the forums, anyone who has done this to 325es 1986 can you help me. I need to swap my E head to I. I have all the parts from a 1987 325ic do you have any diy step-by-steps I can follow and also is this a plug and play or are their more components? Thank you for taking the time to answer me I really appreciate it thanks again.

[Swanny]

I'm in the process of assembling a stock eta block and 731 head to install in my '86 325e. So far I'm planning to use these parts from my '89 325i to swap to Motronic 1.3: engine harness, intake manifold, fuel injectors, throttle body, AFM, 173 ecu.



The issue I'm running into is that I don't want to have to buy a late style radiator and just use the '86 radiator I already have. I understand I need to use the early style water pump with the early radiator, but can I use the thermostat housing from my '89 325i? If I had to use a late style radiator I'm confused about how to mount the late coolant reservoir in the early engine bay.

Looks like its the same part # between early and late models. Should be able to keep the cooling system as is.

[E30 Wagen]

I'm in the process of assembling a stock eta block and 731 head to install in my '86 325e. So far I'm planning to use these parts from my '89 325i to swap to Motronic 1.3: engine harness, intake manifold, fuel injectors, throttle body, AFM, 173 ecu.

The issue I'm running into is that I don't want to have to buy a late style radiator and just use the '86 radiator I already have. I understand I need to use the early style water pump with the early radiator, but can I use the thermostat housing from my '89 325i? If I had to use a late style radiator I'm confused about how to mount the late coolant reservoir in the early engine bay.

[squidmaster]

Are you doing all the internals from the 2.7 block as well? It's the crank/rods/pistons that make it the 2.7L. Other than that, as long as your electronics match up to your head, you'll be good.

Just make sure you include the hall effect cog from the 2.5 engine, and not the 2.7 engine.

You'll notice quite a jump in Tq doing the 2.7 conversion, with a few more HP-- but the real draw is the Tq coupled with the ability to get more power out of the engine with other mods (cams/turbo/valves/ITB) over the 2.5 engine.

[Jimmy85'E30]

Hey there i have a 87 325is and im swapping a E block I had in it. If i get 17# injectors with a intake and the sssquid chip ontop of being the stroker, will this be a noticeable difference?? Also is there anything besides the block that i need from the e motor or is it just the block? Thanks so much!

[squidmaster]

Hi all.

Recently converted my 86' 325 to a 2.7i with parts from an 89' 325i. I am having an issue with the throttle cutting out around above 2500 RPM (hard to tell as I don't have the tach hooked up). The car idles fine, but starts cutting with more then 1/4 throttle applied. If I keep the throttle open, it will rev up for a second, cut off, rev up, cut off, etc. Any idea what could be causing this? It does this at all temperatures and with/without o2 sensor or throttle position sensor plugged in.

The car ran well before the conversion; so I should be able to rule out old parts still on the car (fuel pump, filter) and focus on the new parts.

Did you swap in the 325i AFM? Is it connected?