2.7i vs. 2.7i with super eta pistons and rods

[timmyr77]

Hi r3v. I have a 87 vert with the m20b25. I've had it for about a year and a half and want something more. I was thinking of doing a 2.7i and boosting it eventually but I changed my mind and will dump my money on a 24v swap for a different e30(either a coupe or sedan) but I want to still keep my vert until then. So now that the turbo setup is out of the question I want to know which is better for the money. I have already made a trade with my cousin for a 84e bottoms end. The block was supposedly rebuilt at somepoint. I haven't picked it up yet, but technically I have it. I will be rebuilding my spare 885 head, throwin in hd rocker arms a 272 or 284/272 cam and stainless steel valves, new springs etc. should I invest in the super eta pistons and rods for the bottom end? I've seen people sell them on here for around 200-300 bucks so it's not that big if a investment. I'm not looking for crazy numbers but I would like more torque definetly and some more hp would be good too. So what are you opinions. Thanks
Tim

[Cabriolet]

Hi r3v. I have a 87 vert with the m20b25. I've had it for about a year and a half and want something more. I was thinking of doing a 2.7i and boosting it eventually but I changed my mind and will dump my money on a 24v swap for a different e30(either a coupe or sedan) but I want to still keep my vert until then. So now that the turbo setup is out of the question I want to know which is better for the money. I have already made a trade with my cousin for a 84e bottoms end. The block was supposedly rebuilt at somepoint. I haven't picked it up yet, but technically I have it. I will be rebuilding my spare 885 head, throwin in hd rocker arms a 272 or 284/272 cam and stainless steel valves, new springs etc. should I invest in the super eta pistons and rods for the bottom end? I've seen people sell them on here for around 200-300 bucks so it's not that big if a investment. I'm not looking for crazy numbers but I would like more torque definetly and some more hp would be good too. So what are you opinions. Thanks
Tim

if you can get the easily i would. because as is it seems like you many engine up with kinda meh performance with the stock eta bottom end. however, if you can afford it, have the custom pistons made for the I rods and bring the compression to 9.5+ and you will have a much more enjoyable drive.
stock eta would bring you to 8:1, super eta is 8.5:1 but with all the other work done, i would bet you would really like longer rods and higher compression.

[timmyr77]

if you can get the easily i would. because as is it seems like you many engine up with kinda meh performance with the stock eta bottom end. however, if you can afford it, have the custom pistons made for the I rods and bring the compression to 9.5+ and you will have a much more enjoyable drive.
stock eta would bring you to 8:1, super eta is 8.5:1 but with all the other work done, i would bet you would really like longer rods and higher compression.

Ya I've seen that sometime people have less power then on an I, and that it's not that great if you don't do it right.
The custom pistons sound tempting. How much does that cost? I don't want to drop to much money into this, but I would consider it as it does seem worth it. Thanks for the advice.

[Cabriolet]

http://www.iemotorsport.com/bmw/E30-engine.html

I would call up Andrew at IE and ask them what you need.

[digger]

i wouldnt spend money on a 2.7i if you have a M20B25 engine already, you need a proper build to get a worthwhile improvement over a bolt on M20B25. if you had an eta it would make more sense since the starting point is lower

[Gary Horneck]

I would 2.7i the e block. The i parts just enhance the torque of the longer stroke. Its feels like a different engine to me, mid range torque is instantaneous. I used the 731 head from a EU 323i to keep compression up, and the cam they used on that model is fairly aggressive. I opened up the intake and exhaust ports some, just gasket matching the openings. BavAuto long tubes and free flow 2.5" exhaust. Took my buddy in a Z06 12 runs to beat my times in a NCCC Corvette sanctioned autocross last weekend, so its a quick motor that I run to 6,850 all the time and it loves it.

[timmyr77]

i wouldnt spend money on a 2.7i if you have a M20B25 engine already, you need a proper build to get a worthwhile improvement over a bolt on M20B25. if you had an eta it would make more sense since the starting point is lower

that makes sense in a way, but i want a bigger displacement, and the torque. my b25 has roughley 230k on it, and its getting week. i am rebuilding my spare 885 head. and i have a (again supposedly rebuilt) eta block. if i get super eta pistons, or custom forged pistons from ie, then it seems worth it to me. at this point i dont want to go bigger then 2.7. i have never delt with boring a block, and honestly it intimidates me a bit. i know you have to start somewhere, but i dont have anyone to help me much with that and since im not the greatest wiz with engines, like most of you guys are, i would like to stick with 2.7. it would save me some trouble, headache, and money.

I would 2.7i the e block. The i parts just enhance the torque of the longer stroke. Its feels like a different engine to me, mid range torque is instantaneous. I used the 731 head from a EU 323i to keep compression up, and the cam they used on that model is fairly aggressive. I opened up the intake and exhaust ports some, just gasket matching the openings. BavAuto long tubes and free flow 2.5" exhaust. Took my buddy in a Z06 12 runs to beat my times in a NCCC Corvette sanctioned autocross last weekend, so its a quick motor that I run to 6,850 all the time and it loves it.

Im thinking of putting the regular eat pistons and rods out of the question, now deciding between super eta, vs. forged pistons with higher compression.

http://www.iemotorsport.com/bmw/E30-engine.html

I would call up Andrew at IE and ask them what you need.

thanks again, those would put me over budget, but could definetly be worth it in the long run, especially since i can get them to make the compression i want.

[digger]

that makes sense in a way, but i want a bigger displacement, and the torque. my b25 has roughley 230k on it, and its getting week. i am rebuilding my spare 885 head. and i have a (again supposedly rebuilt) eta block. if i get super eta pistons, or custom forged pistons from ie, then it seems worth it to me. at this point i dont want to go bigger then 2.7. i have never delt with boring a block, and honestly it intimidates me a bit. i know you have to start somewhere, but i dont have anyone to help me much with that and since im not the greatest wiz with engines, like most of you guys are, i would like to stick with 2.7. it would save me some trouble, headache, and money.



Im thinking of putting the regular eat pistons and rods out of the question, now deciding between super eta, vs. forged pistons with higher compression.



thanks again, those would put me over budget, but could definetly be worth it in the long run, especially since i can get them to make the compression i want.

torque is function of displacement but you also need compression (static compression and cam characteristics) and good combustion chamber characteristics.

a SETA piston matches the 885 head but is too low a compression ratio to bother with. you want custom OEM shape pistons about 10:1 if you want a significant bump in torque and this would allow you to successfully run a 270-280 duration cam.

alternatively to avoid custom pistons you could deck the block 2mm and use eta crank and rods, b25 piston. not many people go down this path as it is not ideal taking a lot off the block

[timmyr77]

I agree with you about the oem shaped custom pistons, and higher compression. 10:1 would definitely make a big improvement. I am not going to take anything off the block. Id rather work with the pistons and compression instead. If I'm going with higher compression like that, should I port the intake and exhaust or just gasket match them on the intake, and port the exhaust?

[digger]

best bet is to do basic boltons and save $$ for 24V if you have already decided that path.

if you start a 2.7i build cost will probably escalate out of control, you'll start asking if i get custom pistons why not a bigger crank? then ill need to get the head ported, then ill need a bigger cam, then ill need a standalone computer before you know it you will have spent all your savings

[timmyr77]

so what your saying is just go with super eta pistons and leave it at that.

[digger]

so what your saying is just go with super eta pistons and leave it at that.

swapping seta pistons into your block might open a can of worms and not worth the trouble IMO. Keep it a stock B25 bottom end and add bolt ons......

[timmyr77]

well i have two blocks. a b25, that needs a complete rebuild for sure. And a b27 from an 84e, that although was supposedly rebuilt, i will end up having to rebuild it anyways most likely, so you think throwing in seta pistons will be that big of a deal at that point?

[digger]

doesnt seem worth the effort to me

[timmyr77]

doesnt seem worth the effort to me

really?:( man.... im honestly a little bummed out. I want a little more then just a rebuilt m20, cammed, and full exhaust. i was really excited about building a 2.7i. I think i will still go through with it. Ive started tearing my head apart, and will rebuild that first completely. Once i get a look at my e block, i will decide from there which route to take. i know the seta 2.7i setup wont give me 200hp, but with bolt ons, and a rebuilt head, im sure it will still be a great improvement over what i have now.