Recommended upgrades during N54 build

jackhunter

New Member
Jan 17, 2023
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Hey everyone,
this is my first post on here so I apologize if I am posting in the wrong section or beating a dead horse.
I am currently in the process of rebuilding the N54 out of my 2008 335i. The engine spun a rod bearing, and the cylinder bores were too worn to be reused with standard-sized pistons. The rod journal on the crank for the spun cylinder was also pretty marred up. Because of this, I decided to purchase a good used block with cylinder bores in spec, and a nearly perfect 6 bolt crankshaft so that I can use the 335is clutch and flywheel. My plan is to reuse 5 of the stock piston-rod assemblies and purchase an OEM connecting rod used on eBay. I intend on using standard King main and rod bearings, however I have not decided between ARP and OEM main studs, head studs, and rod bolts. Aside from the plans I have mentioned, I have no idea what I should change while I have the engine apart. The water pump looks to have been upgraded to an all aluminum unit, however I do not know the condition of the HPFP or injectors. Aside from basic maintenance items, do you guys have any recommendations for upgrades while I'm in there? Also, I would appreciate any tips and tricks for building an N54, as this is my first time dealing with an overhead cam engine (I'm used to pushrod V8s).
Thanks!
Jack
 
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Nosrok

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Jan 31, 2017
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Haven't seen many rebuild threads, I've been beating on mine for nearly 100k miles and it's still pulling like a coked up mule, so you might not get a lot of responses. Might also want to try other forums since they've been around longer. Anyway.

As for things to do while you are there:

Engine mounts, Mickey mouse flange, crank block off plate, oil cooler housing gasket (they leak eventually), all the other gaskets but that's normal for a typical rebuild, same with a new belt and tensioner.

Injectors, if they are later versions, 10-12s usually live up to the task.
Hpfp, also had revision but I'm not as familiar with them. Limitations show up on ethanol blends.

If you're reusing stock internals then you won't reach the limits of stock bolts but you will need new ones since they are stretch torque and at that point you might just upgrade if the prices are similar. If I was rebuilding a stock engine I'd use slightly looser ring gaps then what the factory recommends since many problems have come from ring land failures in pistons 4/5, those get the spiciest. Then again I ran 30+ psi on twins for nearly 5 years and never had that problem, I had plenty of other problems but not that problem.

good luck.
 

Sausage

Private
Jul 12, 2022
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What are your power goals?

Regardless of power goals:
You need micrometers to measure all bores (crank, rod, piston)
Check roundness of crank bore. Block and bedplate should fit together perfectly without any edges inside the bores. Most blocks fail here.
Check the oil squirters for proper functioning (spring inside)
Replace ALL bolts
Replace timing chain and guides
Check camshaft bearing ledges for wear. Replace cam if you feel wear
Replace camshaft bearing ledge gaskets (old is metal, new is teflon)
Check (vacuum) the seal of the valves. Clean/replace and grind in valves
Replace ALL valve stem seals
Replace ALL gaskets

Good luck
 

jackhunter

New Member
Jan 17, 2023
5
1
0
Haven't seen many rebuild threads, I've been beating on mine for nearly 100k miles and it's still pulling like a coked up mule, so you might not get a lot of responses. Might also want to try other forums since they've been around longer. Anyway.

As for things to do while you are there:

Engine mounts, Mickey mouse flange, crank block off plate, oil cooler housing gasket (they leak eventually), all the other gaskets but that's normal for a typical rebuild, same with a new belt and tensioner.

Injectors, if they are later versions, 10-12s usually live up to the task.
Hpfp, also had revision but I'm not as familiar with them. Limitations show up on ethanol blends.

If you're reusing stock internals then you won't reach the limits of stock bolts but you will need new ones since they are stretch torque and at that point you might just upgrade if the prices are similar. If I was rebuilding a stock engine I'd use slightly looser ring gaps then what the factory recommends since many problems have come from ring land failures in pistons 4/5, those get the spiciest. Then again I ran 30+ psi on twins for nearly 5 years and never had that problem, I had plenty of other problems but not that problem.

good luck.
Thanks for the insight!
 

jackhunter

New Member
Jan 17, 2023
5
1
0
What are your power goals?

Regardless of power goals:
You need micrometers to measure all bores (crank, rod, piston)
Check roundness of crank bore. Block and bedplate should fit together perfectly without any edges inside the bores. Most blocks fail here.
Check the oil squirters for proper functioning (spring inside)
Replace ALL bolts
Replace timing chain and guides
Check camshaft bearing ledges for wear. Replace cam if you feel wear
Replace camshaft bearing ledge gaskets (old is metal, new is teflon)
Check (vacuum) the seal of the valves. Clean/replace and grind in valves
Replace ALL valve stem seals
Replace ALL gaskets

Good luck
I don't intend on pushing more than 500whp as I want to daily the car and move my current daily to project status. As far as measurements are concerned, my dad used to be a machinist so he's been helping me accurately measure the journals and clearances. I hadn't considered vacuum testing the head, so thank you for the suggestion. I believe my cams and ledges are in good shape, but I haven't taken a super close look yet. I really appreciate the list :)
 

Torgus

Brigadier General
Nov 6, 2016
2,671
2,194
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Boston
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ACF 6466 E92 + METH
I don't intend on pushing more than 500whp as I want to daily the car and move my current daily to project status. As far as measurements are concerned, my dad used to be a machinist so he's been helping me accurately measure the journals and clearances. I hadn't considered vacuum testing the head, so thank you for the suggestion. I believe my cams and ledges are in good shape, but I haven't taken a super close look yet. I really appreciate the list :)

It all depends on how much you want to spend. Throw some new bearings in and #sendit is my advice.

You water pump could be original. My stock WP was aluminum fwiw.
 
Last edited:

jackhunter

New Member
Jan 17, 2023
5
1
0
It all depends on how much you want to spend. Throw some new bearings in and #sendit is my advice.

You water pump could be original. My stock WP was aluminum fwiw.
That was also my dad's advice lmao. I didn't know some of the water pumps were all aluminum from the factory. I thought that was an updated design... Either way, I need to figure out a way to bench test the pump, because the engine overheating is what presumably killed the motor originally. The story I heard from the PO was that the thermostat was stuck closed and the engine overheated badly. He took it to some shop and the morons diagnosed it as a headgasket issue and completely missed the spun bearing. I believe they replaced the water pump during the ordeal, but I have zero faith in their work, for obvious reasons...
 

rev210

Corporal
Feb 24, 2019
235
138
50
Ride
335i - 08 Coupe .
Ideally , since you have the chance you will want a little more ring gap than factory, for the extra power, if sticking with stock pistons. Remember to try and keep the balance weights of the assembly as per the factory setup. May as well smooth out edges in the combustion chamber (very easy to do) even if you don't want to mild port the head.
 

jackhunter

New Member
Jan 17, 2023
5
1
0
Ideally , since you have the chance you will want a little more ring gap than factory, for the extra power, if sticking with stock pistons. Remember to try and keep the balance weights of the assembly as per the factory setup. May as well smooth out edges in the combustion chamber (very easy to do) even if you don't want to mild port the head.
Since I'm going to do the valve seals, I will likely do some minor work to the head. I've never ported a head, so I'm going to be cautious. If I can find a decent guide on N54 porting, I'll go that route, but if I can't, I'll just smooth everything over.
 

IQraceworks

Corporal
Jul 7, 2020
208
121
0
Missouri
Ride
07' BMW 335i
Wanted to ask a questing reguarding my current project build. For a motor that's going to be making a little south of 600hp at 25psi and E40 with twins, are head studs really needed? Or can I got back with a new set of oem head bolts? I'm not planning on ever going any bigger on the power side of things. My current motor cracked a ringland.....so it's getting new pistons and rods. Just wondering if head studs are really needed......it seems rare that I hear about head gasket issues on these motors, especially at power levels under 600hp. Thoughts?
 

BillV

New Member
Feb 13, 2024
15
3
0
Northern KY
Ride
2007 335i (all stock)
What are your power goals?

Regardless of power goals:
You need micrometers to measure all bores (crank, rod, piston)
Check roundness of crank bore. Block and bedplate should fit together perfectly without any edges inside the bores. Most blocks fail here.
Check the oil squirters for proper functioning (spring inside)
Replace ALL bolts
Replace timing chain and guides
Check camshaft bearing ledges for wear. Replace cam if you feel wear
Replace camshaft bearing ledge gaskets (old is metal, new is teflon)
Check (vacuum) the seal of the valves. Clean/replace and grind in valves
Replace ALL valve stem seals
Replace ALL gaskets

Good luck
Good suggestions!
I’m posting for the next person, replace all the orings associated with turbos, coolant and oil lines Along with Gaskets on your charge pipes.
Regarding what to replace, I look at it this way, it’s about your time. Parts are not that expensive in most cases. But if I’ll end up having to tear back into the engine compartment to replace a part I could have replaced while I was already near, I kick myself real hard.