Trent's S54 Rebuild and Sedan Swap

[tlow98]

Hi all,

I've been incredibly happy to find this forum. My heart was a bit broken after the other forum went away, but thanks to all of you that have resurrected this - it's incredible! I previously owned a 2001 IR/Black coupe that I had a lot of fun with. Evolve CSL box, Ground control Coilovers, etc.

Was a lovely car!





Fast forward through marriage, kids, and a decade... I'm looking to have some fun again. This time I'd like to get my hands dirty with a project. I considered a 1M S65 clone, but after owning an E91 I always remembered the E46 with more enthusiasm. So, E46 it is - onward!

Here's the dirty one:



Here's the very clean recipient of the engine, transmission, suspension, etc. :





I picked up the 2002 M3 vert in tattered, but running condition. It has 211k miles and the HG was blown in varying degrees across every cylinder. It's also SMG - that will be swapped... eventually.

My plan was to pull the head and have it decked and rebuilt, but that was not in the cards. I found that the HG failed on the block side first which means some small amount of material has been removed from the block where the HG initially failed. So, likely it is time to pull the whole lump and tear it all down to rebuild it to a further degree.

And here we are after a week of toiling.

[tlow98]

Here is the offending issue - it catches on the finger nail and is recessed. I've removed all the carbon and this is what's left.



I have a few, likely dumb, questions for the group, if I may... Humor me, please.

1 ) Is it customary to reuse pistons in the stock bore at this mileage? If the bores are round and straight could it be honed with new rings installed?
2 ) A bit obvious, but that small nick between the cylinders most certainly will lead to an early failure and needs to be decked/skimmed?
3 ) Would the corrosion alone around the coolant jackets necessitate a deck/skim?
4 ) In general, what is the best ROI I can get for my use case below?

Because I was not planning on this I'm a bit on my heels with the direction to take with the pistons and block - I'd greatly appreciate some feedback and opinions.

Some context - this will not be a track car. It will be a canyon/project/fun car that I build up over time. Not a daily either - used when I feel like it. Somehting I can fly under that radar in and also experience that glorious CSL intake roar when put the skinny pedal against the floor. So, does it need to be in 100% tip-top shape? No. Would I like it to be reliable for another 50k miles? Yes. It would likely take me a decade to accumulate that kind of mileage. I will take it apart and measure everything. If it's out of spec I will replace as needed. I intend to assemble the engine myself which I have done for dirt bikes, but never anything of this size/complexity. I look forward to the challenge. I will sub out the machine work.

I am looking to borrow or rent bore gauges as that's one of the few things I don't have. If you have them I'd be happy to treat them as if they were mine and shower them with care!

Thanks all and it's great to be back here :-)

[Slideways]

1) For stock power, reusing the pistons should be fine as long as the pre-det did not damage them and the skirts and rings are still fine. Mahle Power Pack pistons are 1000 for a set.
2) Due to the damage, safe option would be to deck the block and skim the cylinder head.
3) A deck should take care of this
4) A refresh like this should go another 100-150k street miles

In this DIY - , the owner had the machine shop skim the head 0.16mm to get rid of a mark on the cylinder head. He states that 0.3mm is probably the upper limit and a few manufactures make thicker head gaskets for these engines as well. Best to stick with the stock Elring head gasket if you can.

Edit: Headgasket DIY link - https://forums.m3cutters.co.uk/threa...e46-m3.205525/

Good luck with the build

[tlow98]

1) For stock power, reusing the pistons should be fine as long as the pre-det did not damage them and the skirts and rings are still fine. Mahle Power Pack pistons are 1000 for a set.
2) Due to the damage, safe option would be to deck the block and skim the cylinder head.
3) A deck should take care of this
4) A refresh like this should go another 100-150k street miles

In this DIY - , the owner had the machine shop skim the head 0.16mm to get rid of a mark on the cylinder head. He states that 0.3mm is probably the upper limit and a few manufactures make thicker head gaskets for these engines as well. Best to stick with the stock Elring head gasket if you can.

Edit: Headgasket DIY link - https://forums.m3cutters.co.uk/threa...e46-m3.205525/

Good luck with the build

Thank you. This is very thoughtful and very helpful.

Question - do the Mahle Pistons require aftermarket con rods? They say they have 21mm wrist pins. I’m wondering if the OE wrist pins are different since they call this out?

That UK-based link is great. It’s been my guide up until I discovered the block issue and realized I’ll be going further than expected down this path, ha!

He had basically the same issue I did, only on the head side.

[tlow98]

And here we are. I pulled this larger-than-expected lump and it’s time to start (further) disassembling.



Im tempted to try and do the SMG swap now, as well, but I don’t think that’s wise given the added complexity and possible issues that could cause.

why did the picture upload upside down?

[tlow98]

Hey, look, I found this one seal that appears to not be leaking.

Hooray! Now, time to pull it out.

[tlow98]

Longblock time. I forgot to order a 12mm 12 point. Thursday it shall be.

[tlow98]

Engine all disassembled and at the machine shop. Waiting on parts to arrive.

Feeling a bit bored.

So, what the heck - manual swap time. Time will tell if I regret this 😂

[tlow98]

Ok, data on the 211k mile engine:

Block wear - Bore Taper and out-of-round:
- The bore measured the highest wear in three locations on cylinders #1, #2, and #6 in the non-thrust direction. The value was .0012" = .0305mm.
- In general, the taper was greater in the thrust direction, but the average delta was .0002" = 0.005mm. The greatest taper delta was highest on cylinder 3 @ .0005" = .0127mm. The machinist said for this build that value should not present any issues.
- Out of round was greatest on cylinder #1 @ .0011" = .0279mm. Out-of-round is less important for cylinder sealing and this larger delta should still be ok for my purposes, form my understanding.

Piston Wear
- The pistons were in shockingly good shape. The highest wear on cylinders #1 and #2 is .06mm. The other cylinders were all around .05mm wear.
- The pins, rings lands, and skirts all looked very good. All factory grooving was still evident on the sides of the pistons. Some showed light wear, but none of them were even close to being "smooth".

BMW Total Wear Spec
- The allowable wear limit spec between the block and piston wear is 0.15mm max combined.
- The block and piston total wear, respectively is 0.0305mm + 0.06mm = 0.0905mm
- All the other cylinders + pistons exhibited 0.06 - 0.08mm total wear.

Decision Time
- From the beginning, I wanted to re-use the pistons/rods/pins, but I realize the measurements needed to dictate the path.
- I measured all the above with a $100 bore gauge and a $50 micrometer. I was pretty certain the delta between measurements would be decent with this equipment. The actual values I questioned, of course. So, I asked the machinist to make sure the total wear, taper, court of round, and cylinder-to-piston clearance were do-able. He did not give me exact measurements, but simply said I should have no issues and mentioned total wear was around 50% of spec. He did mention that accelerated wear does happen as things age, especially with abuse, so I should not expect another 211k miles. He loosely said I could expect 100k if the motor was assembled correctly, street driven, and had good quality oil with frequent oil changes before the total wear on the pistons and block necessitate changing. So in other words - best case scenario. Now, tune it, put in cams, and an airbox and I'm assuming you may as well lop off a bunch of those expected miles. He also said BMW specs are pretty conservative and catastrophic failure is mostly related to either extreme wear or extreme abuse if all of the above are good to start with.
- I will re-use the stock pistons + rods + block (honed) and rebuild the head to stock specs.

Machine Work
- A word on prices - I did not get a 'deal', and am not affiliated with this shop, but I'd like to list them so you have a ballpark of what to expect. Please don't hold them to the machinist if I end up sharing their contact with you. That's not cool and prices only ever go in one direction, especially given our inflationary period. Anyway, let's call it "mid 2022 pricing".😁 And of course, this engine isn't running yet, so it's all a bit meaningless at this point.
- Head ~ $900 - 3 angle valve job, surface (.005") pressure test, jet wash, and install new valve guide seals. no guides needed to be replaced nor any valves. Now, I did not measure the valve guide clearance, but I wish I would have. One of the areas I'm trusting the machinists' experience.
- Block ~ $700 - Mag tested, decked (.005"), "boiled" aka cleaned, honed
- Pistons ~ $100 - Clean, change bolts, check all dimensions
- Crank ~ 165 - Clean, check straightness (was great), polish

Machine Work Ramifications
- Head .005" removed
- Block .005" removed
- Block .0005" inches removed while honing
What does this all mean? Well, I'll want to get a .040" head gasket from Cometic instead of the stock .026" head gasket (which they round to .030", FYI) to make sure I don't bump my compression by 0.2 points. In fact, I'll prolly end up lowering it by 0.05 or 0.1 points if my maths are correct. anyone care to comment here? Always looking for a second set of eyes. And for the hone, add that to the total block to piston clearance above, respectively 0.0127mm + 0.0305mm + 0.06mm = 0.1032mm. But remember, this is my math with my mediocre measuring devices. Machinist gave it the OK, so I must not be too far off. This is the worst case for this motor.

Next time, let's talk about rings, main clearances, rod clearances and until then, some pretty pictures! Oh, and also, how not to screw up your brand new main bearings and buy them twice... as I did. Yay! Negative $236, terrific 😀. Rookies have to pay the price!

[tlow98]

This probably doesn’t look like a $236 mistake, but we’ll, it is. All I can say is…
1 - don’t use a plastic scraper tool to remove Plastigauge from a coated bearing.
2 - don’t drop main cap #1 and a new bearing on the front sprocket while trying to fit the cap. If you let the main bearing bolts do the work you will not be broken-hearted caveman like me.

Im actually probably very lucky. The bearing is so soft that neither the sprocket nor the cap show any signs of being nicked.

I just have to buy a whole new set of bearings to replace 1 out of the 14 mains… Yay!

Would this maybe work as-is? Maybe, probably, as our cranks are super hard and the bearings are super soft, but I’m not willing to find out!

contact me if you need extra standard size mains… le sigh.

[Slideways]

Nice progress! Wish there was a video series for this rebuild . A quick search says that a 1 point drop in compression will lose about 4% efficiency, so basically nothing in your case. You could always go the other way and have to run 100+ octane all the time lol. For a stock rebuild, this is looking really good.

Unlucky on the bearing, but at least the cap is in good shape. Looking forward to the next update.

Here is a cool video series on a M52 rebuild that might help for reassembly:

[tlow98]

Yeah, I was considering a video. I could prolly get away with some still photography and white-boarding about engine options with this type of build.

we’ll see!

[heinzboehmer]

This is great! Appreciate you sharing all the details. Gives me confidence in my "supposedly <100k mi, but actually unknown" engine.

I think the machine shop prices are totally reasonable, which is great since you know I'll be checking out the same place. Hope everything else goes smoothly!

About the bearing, not sure which brand you bought, but you can buy individual ones from BMW. Totally get not wanting to mix and maych manufacturers though.

Looking forward to more updates!

[tlow98]

This is great! Appreciate you sharing all the details. Gives me confidence in my "supposedly <100k mi, but actually unknown" engine.

I think the machine shop prices are totally reasonable, which is great since you know I'll be checking out the same place. Hope everything else goes smoothly!

About the bearing, not sure which brand you bought, but you can buy individual ones from BMW. Totally get not wanting to mix and maych manufacturers though.

Looking forward to more updates!

Yeah, I thought for quite a bit on the bearings. At the end of the day, I wanted to use the coated ACL bearings in both the rods and the mains, which is what I bought. Technically, I think the OE bearing mixed with the coated ACL bearings would be completely fine, but something about it just didn’t sit right with me.

if I were using the Kobleschmidt bearings I’d be fine with buying a one off OE, as that is what the koblschmidt are, but I’m not so I didn’t. Perhaps that foolish of me?

Have you had a chance to mic your block yet and check the wear?

[heinzboehmer]

Yeah, I thought for quite a bit on the bearings. At the end of the day, I wanted to use the coated ACL bearings in both the rods and the mains, which is what I bought. Technically, I think the OE bearing mixed with the coated ACL bearings would be completely fine, but something about it just didn’t sit right with me.

if I were using the Kobleschmidt bearings I’d be fine with buying a one off OE, as that is what the koblschmidt are, but I’m not so I didn’t. Perhaps that foolish of me?

Have you had a chance to mic your block yet and check the wear?

Makes sense. I would have done the same thing if I was in your situation.

Haven't gotten around to doing anything with the engine besides cleaning, covering in wd40 and wrapping up in plastic. Still on the MK60 swap. Progress has been slow because of me messing up the new rear brake lines and having to wait for new ones to come in. Currently working on all the electrical bits, think I have a good solution that will save me from swapping out the entire body harness. After the MK60 swap, I have some track days planned, so my hands will be full with whatever I break on the track .

Will probably be getting to the engine late in the year or early next.