ETA w/885 head vs ETA+late model i Pistons w/885 Head

[AWDBOB]

Hey R3V-

I have a ton of engines at the moment and just want to put together something cheap/quick and n/a for a project.

My question is this: how much power is to be gained by shaving an ETA block 2mm and putting late model i pistons in it, over just using the ETA bottom end and putting an 885 head on it?

I've got a good ETA bottom end, but also have spare late model i pistons.

N/A application with IE272 cam and IE long tubes.

If it's going to net me 10hp I'm not going to do a full engine build over it.

I went through the FF M20 dyno thread and have done plenty of research, but results seem varied.

Cheers-

[digger]

done properly the 160-180whp for the 2.7 with decked head. slapping the 885 on an eta is not near that

[georgevongal]

Following up on AWDBOB's question:
trying to build a budget stroker engine.

if you use the stock e crank and rods, with the i pistons, 885 head, intake, etc,... approximately what displacement do you end up with, what compression ratio, and what would be the biggest cam you could go with? Thanks!

[GUERONASTY]

Following up on AWDBOB's question:
trying to build a budget stroker engine.

if you use the stock e crank and rods, with the i pistons, 885 head, intake, etc,... approximately what displacement do you end up with, what compression ratio, and what would be the biggest cam you could go with? Thanks!

Lots of useful information here

https://www.e30zone.net/e30wiki/index.php/M20

https://www.e30zone.net/e30wiki/index.php/Building_a_2.7

[AWDBOB]

done properly the 160-180whp for the 2.7 with decked head. slapping the 885 on an eta is not near that

That's what I was afraid of..... sounds like it's worth the effort.

[ForcedFirebird]

If you check out the dyno thread in my signature, you can see the results of the two combinations. ;)

885 on a stock eta bottom nets about 140whp - about 15whp LESS than a stock healthy motor.

2mm off the block puts you at about 9.4:1 depending on how much the had has been shaved when using "i" pistons, 130mm rods and 81mm crank. I was able to squeak out 180whp/180wtq from this setup, using used parts, just fresh rings/bearings etc, a good valve job (I have tested my seat/back angles for maximum flow without porting), and everything balanced nice.

I was able to source some NOS early Euro pistons (9.4:1 m20b25) that I will be using on 130mm rods, 84mm m52 crank, .5mm off the block to net 10.4:1 compression.

Just be weary of quench when shaving the block - you might not want the full 2mm.

[shawmcbigdis]

885 on a stock eta bottom nets about 140whp - about 15whp LESS than a stock healthy motor. .

Buy this you mean a sticker m20b25 correct? But I would say 140whp if starting with an ETA is a heck of an upgrade. Sent from my Pixel XL using Tapatalk

[ForcedFirebird]

Buy this you mean a sticker m20b25 correct? But I would say 140whp if starting with an ETA is a heck of an upgrade. Sent from my Pixel XL using Tapatalk

It's a slight upgrade if you have an eta, but not by much. Stock healthy eta's do about 120whp and a little more when chipped. Local friend has an eta race car, it's at 125whp with no accy's and open exhaust. The biggest thing is you kill the TQ -you drop about 30wtq to get that ~15hp.So, if you are starting with an eta, it's an upgrade, but you are going backwards if you already have a b25.

I was only able to get 145whp on one 885/eta combination, most are lucky to see 135.

[shawmcbigdis]

It's a slight upgrade if you have an eta, but not by much. Stock healthy eta's do about 120whp and a little more when chipped. Local friend has an eta race car, it's at 125whp with no accy's and open exhaust. The biggest thing is you kill the TQ -you drop about 30wtq to get that ~15hp.So, if you are starting with an eta, it's an upgrade, but you are going backwards if you already have a b25. I was only able to get 145whp on one 885/eta combination, most are lucky to see 135.

Ohh I didn't realize it dropped that much torque. That sucks. My plan was to do a dirt cheap head swap only first, then down the line upgrade the Pistons and all that. But it sounds like I might be better off just holding on to the parts and doing it all at once. Loosing that much torque would also make it an absolute necessity to upgrade the dif, as sticking with the 2.93 would be abysmal with even less torque. Sent from my Pixel XL using Tapatalk

[ForcedFirebird]

If you just want to swap the head, use a 731 head and install 885 valves and cam in it. IT doesn't flow quite as well as an 885, but it's a nice upgrade for a 2.7 flat piston rotating assy.

[shawmcbigdis]

If you just want to swap the head, use a 731 head and install 885 valves and cam in it. IT doesn't flow quite as well as an 885, but it's a nice upgrade for a 2.7 flat piston rotating assy.

A lot harder to find though, especially for dirt cheap, line I can an 885 head. Sent from my Pixel XL using Tapatalk

[ForcedFirebird]

True, but you will be eliminating the need to get "i" pistons, machinist shaving the block etc. If you added it all up, bet it's close to a wash at the bottom line. Also saves you a bunch of time to boot.

[AWDBOB]

Awesome, thanks John. I was just trying to avoid bottom end work if possible, hence the questioning of the efficiency of the 885/eta combo.

My current line of thought is to just use the i block I have with the i pistons, shave the deck, and reassemble with the ETA crank/rods so the rings are still mated to the same bore. Just trying to get a bump in power without doing a full bottom end rebuild.

[shawmcbigdis]

True, but you will be eliminating the need to get "i" pistons, machinist shaving the block etc. If you added it all up, bet it's close to a wash at the bottom line. Also saves you a bunch of time to boot.

That's some very good points. I think it will shift the focus of my head search. Thanks Sent from my Pixel XL using Tapatalk