Engine Rebuild Advice - To Remove The Head Or Not?

[Syfon]

I spun cylinder 3 rod bearing a while back.

Bit of background;

• 13 March 2004 build
• 93,000KM at time of spun bearing
• Owned since 50,000KM
• Oil changed every 5,000KM with Liqui Moly Race Tech GT1 10w-60
• Never revved above ~4,000rpm until oil is at least 80C

Engine is out of the car and crankshaft is out.

Cylinder # 3 rod bearing spun quite badly, and the corresponding crank journal was damaged (if I run my fingernail across the journal it does catch!). Main bearing # 4 has chunks taken out of it, the corresponding journal is damaged but still quite smooth.

I took the crankshaft to a local machine shop; the owner advised me to remove the head and replace rod # 3 as he is unable to machine the rod due to it being of a "cracked" design.

What is the best plan of attack here?

Am I better off replacing the crankshaft with a good used one (undamaged obviously) and keeping all the stock pistons/rods (i.e. just replace rod/main bearings and rod bolts and put back together, thus avoid removing the head)? What about cleaning and/or flushing the block/head to remove any trace of metal? I cleaned the sump yesterday and there was a lot of copper flake in there...

Or do I go down the path of removing the head, replacing rod # 3 (with an oem one), having the crankshaft machined/straightened, and putting slightly oversized bearings?

I've never built an engine before, so this is all new to me. I'm quite mechanically inclined but unsure what the best option is in these circumstances?

I'm thinking of doing the following;

• Remove valvetrain & head
• Remove rod/piston #3 (replace rod #3)
• Have everything ultrasonically cleaned
• Machine crankshaft rod & main journals (machinist also advised the crank will more than likely be bent by 2 or 3 thousandths of an inch)
• Rebuild with existing pistons/rods, corresponding oversized rod/main bearings
• New oil pump
• Bulletproof VANOS
• Replace all gaskets/seals/etc.

Cost is a pretty big factor here. I don't really want to go down the path of buying lightweight/forged JE/Carillo pistons/rods, however on the flip side I'm thinking of doing it along with cams as the motor is out. When in Rome lol

Keen to hear the advice from those who have rebuilt their S54 and what they did. The M3 has been off the road since July 2019, so I'm keen as a bean to get the ball rolling and rebuild my motor!

EDIT: Head came off a while ago and everything has gone to machine shop!

[Jersey_M3]

Swap it with an s58. Or just buy a new motor. Although. I have never rebuilt an engine.

[eacmen]

At least remove the head and change the gasket. If there is any wear on the stock internals then change it. Otherwise just leave it be.

[Arith2]

Probably should avoid Liquimoly for now on. Everything you're thinking of doing maintenance wise sounds good. Do it while you're there. Could get the ARP head studs also. Cams cost, you should ideally do rocker arms but that tune on top of cams and all the maintenance adds up.

[Syfon]

Swap it with an s58. Or just buy a new motor. Although. I have never rebuilt an engine.

Lol I wish. 2nd hand motors are pricey down under...

At least remove the head and change the gasket. If there is any wear on the stock internals then change it. Otherwise just leave it be.

Yep. Sounds like the logical thing to do.

Probably should avoid Liquimoly for now on. Everything you're thinking of doing maintenance wise sounds good. Do it while you're there. Could get the ARP head studs also. Cams cost, you should ideally do rocker arms but that tune on top of cams and all the maintenance adds up.

Can't definitively say the oil was the problem here. I had 3 oil analysis done in the past all on the LM; each report came back with no abnormalities. Last oil analysis was done ~90,000km, so oil at the time the bearing spun was ~3,000km old. If it were run solely on Castrol TWS (or whatever the correct spec Castrol oil is for the S54), I'm sure the same problem would have arisen.

That's my mentality atm. It's all apart so it would be a massive waste to not do a heap of other maintenance. If the head is coming off then yeah ARP studs will be used. Re cams, I remember reading on old M3Forum you aren't required to replace anything if you go with Cat Cams 280/272. Simply drop them in, time correctly, tune and go. I need to research this much more.

[FBloggs]

Bite the bullet and save/search for a good low mileage s54 with provenance. Replace the bearings in it and put that in the car . Then part out you current engine to recoup funds.
If you want your engine numbers to match your VIN, do it properly.
switching rod bearings and turning the crank is not a rebuild. It is false economy. Imo of course

[Syfon]

Bite the bullet and save/search for a good low mileage s54 with provenance. Replace the bearings in it and put that in the car . Then part out you current engine to recoup funds.
If you want your engine numbers to match your VIN, do it properly.
switching rod bearings and turning the crank is not a rebuild. It is false economy. Imo of course

Low km S54's go for $15k aud. That's just under $10k usd. Cheaper to rebuild my entire motor with forged/ltw internals lol.

I very much want to keep the original engine with the car, so rebuilding this one is my only option.

Keen to hear from some members who have actually rebuilt their own S54.

Edit: For reference, someone in Victoria is asking $15k aud for their s54+getrag420g. https://www.gumtree.com.au/s-ad/lara...box/1238676621

Another one with ~80k km sold for $12.9k aud https://www.ebay.com.au/itm/BMW-E46-...-/292409310891

[Arith2]

After all my maintenance items and then engine, I'm at about $7000 for my 85k mile engine. In reality that's not bad. I found my alternator to have astronomical amounts of radial play so you'll probably find other items that need replaced

[jbfrancis3]

I don't know the definitive answer on need to remove the head. There may not be one but once you get some responses, you'll probably see people clustering in the safe zone saying to inspect it.

Onto more exciting bits, I know you mentioned cost was a big factor. But you also said when in Rome...

So given that, if I spun a bearing tomorrow, which should happen according to Arith2, I would call up Lang Racing and discuss their stroker kit. Not only would you come out net positive from a power perspective, you are getting a better designed assembly. I believe with 3.4L of displacement, there is no change to bore size but if you sought 3.5L, you'd need to bore out the block. Anyway take a peek: https://store.langracing.com/bmw-s54...l-stroker-kit/

[Arith2]

So given that, if I spun a bearing tomorrow, which should happen according to Arith2

What are you talking about?

[bigjae46]

if you spun the bearing, you need to replace the rod. You can replace just the one rod. Ideally, you’d pull the rods and pistons and balance them.

Sounds like you need to grind or turn the crank. VERY important - you have to heat treat it. You’ll be removing the hardened layer on the journals. Need to re-treat.

At least in the US, it’s almost cheaper to just buy a BMW reman crank. If Lang Racing is still doing crank repairs...that would be the option I’d go with.

Someone recommended ARP head studs. I think that is a waste of money, OEM head bolts are fine. Never heard of one being an issue.

[cozmo kraemer]

I am in the process of a spun bearing ordeal. I bought what was a low mileage engine out of a convertible to do a refresh on, vs doing a stroker with my spun bearing engine... and at this point, I almost think it was a mistake. I am a finance guy for a living, was keeping track of everything in a spreadsheet...and now I dont even want to look at it. I get so particular, I get the 'while you are in there' mentality, and now I have basically pieced together a brand new freaking engine.

So it really depends on what you want. If you just spun a bearing in a more minor way (rod knock but still runs), I would not recommend removing the head. If compression and leak down are good. Leave it in place. Remove it and prepare for cascading expenses.

[George Hill]

if you spun the bearing, you need to replace the rod.

100% correct. You'll need to pull the head to get the rod/piston out. They are a balanced set so you'll need to find a heavier rod and lighten it to match the other 5 or lighten the other 5 to match your new rod.

[ethan]

That's my mentality atm. It's all apart so it would be a massive waste to not do a heap of other maintenance. If the head is coming off then yeah ARP studs will be used. Re cams, I remember reading on old M3Forum you aren't required to replace anything if you go with Cat Cams 280/272. Simply drop them in, time correctly, tune and go. I need to research this much more.

If money matters and you can't find a cheap used swap, then just pull the engine apart and have a shop measure everything. Replace your rod, balance it, and find a good crank. Use stock parts everywhere (including head bolts and especially the timing tool.) It's a geat engine stock.

Most fun per $ after that? 280/272s and a proper CSL airbox/stock CSL tune together. Use the stock followers (don't bother with the DLC coated stuff for double the cost of the cams.)

Once you're beyond that, you have to not care about what else you could do with the money.

[Syfon]

So last night I removed the head. No issues at all with the head gasket or anything else for that matter. Bores look perfect, as do pistons.

I'll be keeping the stock pistons/rods. Replace rod # 3, have everything balanced, crank machined and get it back together. Just need to piece together a comprehensive list of parts I require.

Hoping to have everything done and engine/trans in by the end of winter (Aug-Sep)!