M20 knocked. Want some advice pls

[timmyr77]

By m20b25 knocked this week. Rods went out in my vert. Absolutely horrible timing because I'm low on $$$ since I just had my car resprayed. The 2.7i build always was interesting to me. I have an eta with a block that was rebuilt 150k ago. Would you guys recommend for me to do the 2.7i build on it if my head turns out to be alright and the block is good to (I haven't looked at the internals of it yet)? I want to keep things as cheap as possible since I'm saving for a build still that will start in November. If I was to do the 2.7i, I'd ibviously get new hg and head bolts, change the front and rear main seals and some other gaskets. Please give any advice you have. I'm basically car less for the next week and need to decide what I'm gonna go with. Thanks!
Tim

[Gary Horneck]

As a satisfied 2.7i builder, I would say do it. My e block had almost no visible wear, 165k on it when I did the first 2.7i. I did full rebuild on the block 3 weeks ago, everything was well within factory specs, so bearings and rings. Simple, fast, rebuild.

[Swanny]

Get the head checked. If its straight then why the hell not...just a few bills in seals and you're back up and running. Biggest question is what pistons were in the eta? There's one combination that lowers the compression to not fun numbers

[timmyr77]

M20 knocked. Want some advice pls

Get the head checked. If its straight then why the hell not...just a few bills in seals and you're back up and running. Biggest question is what pistons were in the eta? There's one combination that lowers the compression to not fun numbers

The engine is from an 84e. So I'm not sure if that makes a difference. It's not the super eta is what I know for sure. Did the 84/85 e's have different pistons from 86/87?

As far as my head goes there shouldn't be any cracks (except one on the outside that is about t 5mm long and hasn't affected anything yet. I already talked to someone who said they would be able to repair it) so I'll take it to the shop to get inspected and resurfaced.
Well two yes's so I'll be pulling both engines apart tomorow and hopefully by the end of the week it will be back together and running. Any more advice appreciated

[jmc1590]

The pre 87' eta uses flat pistons to match the 200 head. '87 (3/87 I think) and later (super-eta) use a domed piston that matches the 885 head.

When converting to a 2.7i, the domed pistons are the preferred of the two. No compression change - stays at ~ 8.5:1. When using the flat pistons with the 885 head, the compression does drop to ~ 8.4:1. (Flat pistons w/ 200 head is ~ 9:1)

Having build and driven both types of builds, I don't see a major problem either way. They both run great!

If you have all the parts on hand, I'd say do it. Plenty of threads on the process here. Just remember to ask if things seem out of sorts.

[timmyr77]

Well ya I know I have the flat top pistons that seen from the super eta. I got a little confused to whether there were different flat top pistons. If I had the choice of a domed pistons id go with it but id rather save money and use what I have. So since I already have an I , all I have to do is put all the I components on the eta block. I read that there are some idling issues with the flat top pistons because of the chamber difference and that a tune can fix it. I have a dinan chip on my current 173 ecu. Would/could that fix the problem of should I have a tuned chip for the set up made

[ForcedFirebird]

Since you have a 325i already, just swap the rotating assembly. It will make less power than a b25, but has more torque. Will pull harder from a stop, but runs out of steam above 6k rpm.

Your swap is simple, it's when you start with an eta car that there's a lot more swap related items to deal with.

[timmyr77]

Well I doubt it will make much less power then my b25. It was a tired engine and seeing that the Rods went out at 230k doubt it was well taken care of before me. I'll keep the head stock maybe gasket match the exhaust if I have time. And I'll be getting a chip from SSS squid most likely hopefully help the top end out. I'm not to conserned with it being slightly less powered. From what I understand te power curve is a lot flatter and that's what appeals to me. I'll be pulling the engine out in November again and doing my swap through the winter. The 2.7i is just so I can drive it till the.

[AndrewBird]

You might get away with just replacing the bearings. It will give you some time to save up for a full re-build or swap. Assuming you didn't run it until it blew that is. Bearings could be swapped out in an afternoon/weekend without pulling the motor.

[timmyr77]

No the engine just started knocking. Not driving it anymore. Borrowed my parents spare car till it's done. Ya that was an option and it will be the case if the eta block will be bad.

[ForcedFirebird]

We have dyno'd many many m20's. Tired, they will make 130-140whp. In good condition and mileage, they make 150-ish. Rebuilt head on tired bottom makes 145-155. eta bottom and i head, rebuilt/tuned/race ready (only resonator, no accys, chipped) made a max of 145whp/170tq. In comparison my 200+ mile b25 (odo was broken 2 owners ago) makes 148whp/147wtq.

[timmyr77]

Well I doubt mine made over 135whp. It was tired and not taken care of. So if it makes 135-140 I will be very happy. I'm more interested in a flat power curve because it was dead in the bottoms before. No bottom end torque at all. The bottem end on the eta was rebuilt 100-150k ago. If everything is good when I take a look tomorrow or so I won't be touching it. This isn't my primary build either way. I just want something different and reliable now that I have no choice but to work on it. If it woulnt have broken I would never touch it. Since it has. I figured I'll use the parts I have and go through with the 2.7i

[ForcedFirebird]

Well I doubt mine made over 135whp.

Actual data, tired b25's will be as low as 120whp, specially if there was failing electronics. A broken TPS will make low power for instance, since the ECU will not ignore the o2 in WOT as it should.

As long as everything is in good working order after the repairs, they feel like brand new engines once gone over.

[timmyr77]

Well everything worked on it. It sounded healthy and idled fine. It did burn oil an I when you pushed it, definetly felt tired. So I think with a freshened up head and better block It should drive much better

[timmyr77]

Pulled the head. Doesn't look healthy at all. Gonna do a leak test. Get it polished and resurfaced, Change valve seals, lap the the valves if needed. Anything else I should consider?