DIY Engine Swap & Rebuild Progress

[rhodesman]

For those of you who are interested in the process to rebuild and engine or swap it out with a new one, I am doing both LOL.

Some back story: I was being stupid and on a high speed run, I wasn't paying attention and ended up melting my Cyl-4 piston rings and subsequently the cylinder walls along with it. the O2 sensor went flat for some reason (was basically brand new) and I didn't notice the AFRs flatlining and thus the ECU just kept dumping fuel into bank 2 to compensate until it went 'boom'.

I bought a new (used) engine block to replace by blown engine block. I bought new pistons and rods, new bearings, all the bits you would need to re-assemble the engine and various tools needed to make the process less painful. Disassembled the new block and got it ready to head to the machine shop to be flattened and cleaned. Now I'm in the process to pull the old engine so the head can also go out and be machined to perfection with the (new) block.

In balancing the rotating assembly, I followed the normal guidelines of match the lightest piston with the heaviest rod and so forth. However, being a software engineer, that wasn't good enough so I wrote a python program that inputted a csv file of all the weights and then ran through all the permutations and found the best matchups for the smallest variance in weights. Doing it the traditional way I got a weight variance of 1.4g. My python script was able to drop that to 1.3g. Might not seem like much but the closer to 0 you can get, the better. Plus it was fun little 'side quest' in my whole engine build process. The repo for the script can be found here.

The current state is I have the engine ready to remove. Tonight I'll pull the engine itself and begin the disassembly process.

For when I begin the rebuild process, I ordered one of those inflatable clean rooms which I'll blow up in my garage so the engine has the best chance of being contaminant free when it all goes back together. This wasn't really what I was planning to do this summer with my car, but I actually am enjoying the whole process, plus I really wanted to remove the engine just so I could clean the engine bay.

Further note: This is quite the process and I would not recommend it to the faint of heart. I have been scouring the forums, reading ISTA-D like it's a book, and have printed out almost an entire ream of instructions/directions. I have spent more money on parts than a normal human would have bothered with but my goal is a bulletproof engine that can take anything I throw at it.

More updates to follow as I continue.

 

[rhodesman]

Next Update:

Finally pulled the engine and transmission, what a PITA that is when you do it by yourself...lots of dad noises were made. I started to remove the accessories from the engine but lost steam around 1:00am so I called it quits for now.

Next update I'll hopefully have the head off so I can finally see the carnage with my own eyes. I hope the head is okay but when I borescoped it, it looked fine. On the intake side, there's a pool of oil sitting in the intake chamber. I'm not sure how the oil got in there, I assume from the blown piston rings just shooting oil up into the combustion chamber but that seems crazy to me. Only Cyl 4 had oil in it, all the others looked fine so who knows. I'm sure removing the head will reveal the answer.

Inspected the Turbos and they look good. I did find a massive hole in the outlets due to the silicone hose proximity to the manifold. I have larger aluminum outlets but they still require silicone hoses to connect to the turbos. An oversight on my part because I could have bought the turbos with the clap connectors but I didn't. Now that the engine is out, I can easily setup a more robust connection that's shielded better from the heat.

!!! PLUS !!! I found a 10mm socket resting in the subframe that I lost almost a year ago!

 

[rhodesman]

I forgot to mention, I have a server running in my house that has a full ISTA-D and ISTA-P database setup along with all the old school programming tools from before ISTA was available. However, having that in the garage can be annoying trying to find the right instructions and then digging down through the instructions to find what you need.

To fix the headache dealing with computers in the garage, I went through the arduous task of going through each section of the engine maintenance procedures in ISTA-D and printed them out. Then I put them each is plastic sleeves in a 3-ring binder. It was a painful and tedious process but I now have everything (including all the torque and measurement charts) in a single binder, easy to grab and it's organized from in car work to engine out work.

 

[rhodesman]

Went out of town for a few days but I'm back at it.

I pulled the head and sadly, I have to scrap it. There were cracks from both intake ports that went to the spark plug so it's no bueno. Thankfully, I had just purchased an entire MT kit off a junked 335i. Before the company had packed it up to be shipped, I was able to ask them to pull the head off that car and it was good (minus extensive carbon build up but that's easy to fix). They threw that onto the pallet being sent out so I'll have a new head along with a MT swap! I also decided since I needed to have the head cleaned and leveled anyways, I was going to polish the ports for that extra little 'kick'. I have port injectors so I don't anticipate the ports needing to be cleaned again.

Other carnage I found was the reason I needed to pull the engine, Cyl 4 was toast, like toasty-toast. Good ol' melted head FTW.

I'm waiting on the pallet of parts to arrive. They said today but looking at the tracking it might not be here until tomorrow or Friday. Hopefully I'll have it all before the weekend so I can remove the valves and have everything ready to go to the machine shop Monday morning. More to come!

 

[wheela]

Holy smokes, toasty toast is putting it lightly

 

[rhodesman]

For today's update, it's Good News! The final pallet of parts arrived and I now have everything to rebuild my car. Well okay, I still need to buy a clutch but I'm having a hard time trying to decide. I want a clutch that can handle at least 1,000 ft/lbs of torque. I understand the tradeoffs but this isn't a daily driver and I don't drive it where there's traffic so I'm okay with a heavy clutch. Besides, it will incentivize me to not skip leg day LOL.

This weekend was all about cleaning. I wanted to clean the engine bay, all the parts I received and then start the process of cleaning all the little things using my brand new ultrasonic cleaner! I am so excited to have parts that will look brand new. The biggest job was definitly the intakes from the used head I received. The guy said it was dirty, but my god was it dirty! I'm surprised the car ran at all with the amount of gunk that was built up. Anyways, nothing like a few hours at the work bench and some sea foam fumes to occupy my Saturday evening and I must say, the results are quite impressive. I also took the opportunity to model and 3D print a tray to old all the valves and parts so I can keep them organized and hopefully I wont loose anything. It's not the best design, but good enough for my needs.

so dirty!!

Much better! I know I could probably gone further by doing a dry ice blast or something like that but I couldn't find anyone near me that did commercial dry ice blasting and well, a large spray bottle of degreaser and a power washer are still a decent alternative. I do have some paint touchups on the frame rails I need to address but a simple can of black rattle can will solve that pretty quick.

I didn't take any before pictures but considering the extent of filth the valves were in, you can imagine the transmission was almost black.

I also scrubbed and washed out 110k miles of bugs and leaf bits from the radiators and tried my best to de-stain them but that would probably be best with an ultrasonic cleaner....that was 8 times larger than the one I got.

Testing out the ultrasonic cleaner and parts are looking pretty dang good.

How did these valves still work!? I will say, these took an entire day by themselves and 4 different methods to fully clean. I still need to run them through the buffer to get the squeaky clean, but my god what a difference!

The results:

I do plan to hit the exhaust valves with a wire wheel to try and get some of that burnt carbon off but it's really not that bad so I'm not too concerned about those.

The final cleanse was the garage itself. I could barely walk around before plus there was dirt and drops of oil and coolant all over the place.

Fun note: the battery is disconnected as it should be for this, and I accidentally bumped into the trunk and now I'm locked out of it. I think I can put the battery charger on it to power it up enough to open it..I hope because I also locked myself out of the cabin. The windows are down, but the doors are locked. Always something.

Next up is taking the head and block to the machine shop to be honed and then I can finally start the process of rebuilding!

 

[rhodesman]

Just a quick update. I finally finished cleaning the intake ports last night. I cannot tell you how satisfying it was to run a towel through them and have it come out clean.

 

[wheela]

Wow, you did a great job cleaning those up Reminds me of cleaning rifle bores, it always amazes me how you can get that bore looking mirror polished, but the swabs still keep coming out dirty. It's so hard to get it fully clean.

 

[wheela]

Those aren't cracks on the sides, are they? Assume they must be some kind of parting line from original casting?

 

[rhodesman]

Those aren't cracks on the sides, are they? Assume they must be some kind of parting line from original casting?

Yeah those are casting lines. The head is at the machine shop now so it's getting a full chemical bath and I'm sure they will let me know if they find any kind of cracks but I doubt it.

 

[IQraceworks]

As far as balancing the rotating assembly goes.....don't you want to stay as close to the factory pin/rod weight in order to keep the entire assembly in balance? Just having the rods and pistons close to the same overall weight, doesn't take into account the crank when it's spinning, or the weight variances between the big and small ends of the rods. Or did you also send the crank out to get it balanced?

You are just weight matching components, not really balancing the rotating assembly.

Right?

 

[rhodesman]

As far as balancing the rotating assembly goes.....don't you want to stay as close to the factory pin/rod weight in order to keep the entire assembly in balance? Just having the rods and pistons close to the same overall weight, doesn't take into account the crank when it's spinning, or the weight variances between the big and small ends of the rods. Or did you also send the crank out to get it balanced?

You are just weight matching components, not really balancing the rotating assembly.

Right?

.... damn it, you're right. I did not consider that.

Ugggggg this project in itself has just become a total money pit LOL. I mean, who needs a savings account anyways!?

 

[rhodesman]

I called up the machine shop that's honing the head (they build BMW engines there so it's not just a machine shop) and they said they don't do rotating assembly balancing but they do farm that work out to a third party. They told me what I need to bring and how it should be setup for them to do the balancing so I'm going to work on that this weekend if I can. Other than that, I'm working on ordering the clutch and flywheel and a few other little bits I noticed I didn't have.

Funny side note: The machine shop keeps trying to sell me on doing a closed deck block so I can achieve 1,000+ bhp and I keep trying to tell the guy "dude, it's a convertible, it would twist the chassis into a pretzel!!" Anyways, I know he's just trying to upsell me because that's where he'll make his money but there is no way in hell I'm doing that, it's pure insanity.

 

[rhodesman]

One more thing! As I eluded to previously, I have been using AI (ChatGPT 4o) to help me through this build process. I've never built an engine before so I view this as a learning opportunity. I must say, AI has been critical in having a "teacher" by my side to help with engine dynamics I know little about and verifying I'm setting up the engine with the most optimal configuration possible.

 

[wheela]

One more thing! As I eluded to previously, I have been using AI (ChatGPT 4o) to help me through this build process. I've never built an engine before so I view this as a learning opportunity. I must say, AI has been critical in having a "teacher" by my side to help with engine dynamics I know little about and verifying I'm setting up the engine with the most optimal configuration possible.

View attachment 98244

Very interesting, but a word of caution. With AI, trust but verify. Sometimes it's wrong, but won't know it's wrong. Or it can misunderstand context and give an answer that may be correct for a different context, but not necessarily your own context. As an example, I saw somebody had requested it to write a scholarly article about some subject matter, and it did - even included references. However digging into what it wrote, all the references were fabricated. It was smart enough to know it needed references, but not smart enough to know the references needed to be real.

I know nothing about balancing a rotating assembly of an engine. But if you're including the crank in the balancing (vs. just weight-matching piston/rod assemblies) wouldn't you need some information regarding the crankshaft's state of balance as an input when figuring out how best to arrange the weights of your piston/rod assemblies? Maybe not

 

[rhodesman]

Very interesting, but a word of caution. With AI, trust but verify. Sometimes it's wrong, but won't know it's wrong. Or it can misunderstand context and give an answer that may be correct for a different context, but not necessarily your own context. As an example, I saw somebody had requested it to write a scholarly article about some subject matter, and it did - even included references. However digging into what it wrote, all the references were fabricated. It was smart enough to know it needed references, but not smart enough to know the references needed to be real.

I know nothing about balancing a rotating assembly of an engine. But if you're including the crank in the balancing (vs. just weight-matching piston/rod assemblies) wouldn't you need some information regarding the crankshaft's state of balance as an input when figuring out how best to arrange the weights of your piston/rod assemblies? Maybe not

You're probably right about the crankshaft and there is still a lot to look at numbers wise, I'm definitely not done. I just was sitting here wondering if the balance/weight of the pistons and rods would be a factor in the stage of the rotation in the motor. I did go out to the garage and manually cranked the blown engine (since it's bottom end is still intact) and I worked with ChatGPT to correct the math to better reflect the actual piston positions through the 4-stroke cycle.

In the N54 engine, the cylinders rotate in pairs. Obviously they are opposite strokes from one another due to the firing order. What I find interesting is that when Cyl 1 & 6 are top dead, the rest are all even with each other in the block but two are going up while two are going down. The pairs are:

• 1 & 6
• 2 & 5
• 3 & 4

I worked with chatGPT to understand the correct stroke cycles for each cylinder with those pairings. I'll spare you the back and forth I went through with ChatGPT (it took over an hour to get it all sorted) for her to understand the correct cylinder placement throughout the crank rotation. However, I got some clarification on the varying weights and she changed her output to reflect the paired cylinders and their respective movements through the 4-stroke cycle. I attached a text file with the full explanation and output since it's a lot.

The summery of her calculations are as follows:

Revised Weight Assignment:

1. Cylinders 1 & 6:

    •    Cylinder 1: Lightest weight (1023.0) is balanced against the next lightest (1023.1).
    •    Assignment:
    •    Cylinder 1: 1023.0
    •    Cylinder 6: 1023.1

2. Cylinders 2 & 5:

    •    Cylinder 5: Heaviest weight (1024.3) is balanced against the second heaviest (1024.1).
    •    Assignment:
    •    Cylinder 5: 1024.3
    •    Cylinder 2: 1024.1

3. Cylinders 3 & 4:

    •    Cylinder 3: The remaining weights are close (1023.8 and 1023.6), so they are paired together.
    •    Assignment:
    •    Cylinder 3: 1023.8
    •    Cylinder 4: 1023.6

I have no idea if this is useful or even necessary but I do find it interesting and curious what someone with some experience in engine balancing and building has to say about it.

 

[rhodesman]

I know nothing about balancing a rotating assembly of an engine. But if you're including the crank in the balancing (vs. just weight-matching piston/rod assemblies) wouldn't you need some information regarding the crankshaft's state of balance as an input when figuring out how best to arrange the weights of your piston/rod assemblies? Maybe not

To answer your other question/point, yes, the crankshaft weight and balance does factor here. That's where I have no idea where to begin and am going to take everything to someone who knows what the F--- they're doing and have the proper equipment to do it.

I'm really just playing with the data and learning what I can as I do find this whole process fascinating and my desire to learn is sending me down multiple hour long rabbit holes to better understand. I even started to model and 3D print various tools I've seen people use in youtube videos so I can replicate their testing conditions here.

I'm just nerding out to all this.

 

[jzx_andy]

HP Academy might have some useful info on engine balancing if you're prepared to spend on their courses

 

[JohnDaviz]

now this is pretty cool.

Not sure if you did it already. But one thing i really recommend (ask me why) is to check the main alley for straightness. You don´t want to be at the point of assembling the engine and the crank doesn´t rotate.

 

[rhodesman]

A small update today. Sorry it's been quiet but I'm still waiting on the machine shop. I feel like they bamboozled me because I was under the impression I would get the head back in a week and it's now been two and it's still not done

However, while I wait, I've just been doing more cleaning work making use of my new ultrasonic cleaner. This thing is amazing and at the very least, the engine will be squeaky clean when it all goes back together which makes me happy.

My kids asked me what I was doing so I told them I was making robot soup. I have a few more accessories to clean and a few hoses and everything will be like brand new.