Technical #4 Cylinder is dead…any ideas as to what caused the failure?

[IQraceworks]

Thanks, the bigger gap makes sense for higher power levels.

I was curious where 0.009" landed in the stock clearance range. Since your piston broke and a lot of people push the stock internals to similar power levels, I was curious if your's perhaps fell on the low end of the clearance range compared to others who haven't broken their pistons. I think 0.009" seems to be pretty much right at nominal for the range?

Are you planning on measuring the gaps on your other stock pistons for comparison?

I hadn't planned on measuring any of the rest of them, but I guess I could. I've measured several in a used N54 I bought a while ago, and they were all around .010"-.012".....so the .009" gap is the tightest I've seen.

Since I ordered Mahle forged pistons, I was looking at the data they list for piston ring gaps...and they are saying you should be running around .020"-.022" for a 3.3" (84mm) bore. So you figure, that's double what the factory ring gaps are. But...the oem gaps were set up for a 300hp motor at 8-10psi boost, not 600hp at 25psi boost, so it's not like it's BMW's fault.

I just got done ordering all of my parts (Mahle forged pistons, Manley H-Beam forged rods, King bearings, Elring HG, and yes...I went with new OEM stock head bolts. I figured that at 575-ish hp, the stock bolts should be fine.

 

[wheela]

I hadn't planned on measuring any of the rest of them, but I guess I could. I've measured several in a used N54 I bought a while ago, and they were all around .010"-.012".....so the .009" gap is the tightest I've seen.

Since I ordered Mahle forged pistons, I was looking at the data they list for piston ring gaps...and they are saying you should be running around .020"-.022" for a 3.3" (84mm) bore. So you figure, that's double what the factory ring gaps are. But...the oem gaps were set up for a 300hp motor at 8-10psi boost, not 600hp at 25psi boost, so it's not like it's BMW's fault.

I just got done ordering all of my parts (Mahle forged pistons, Manley H-Beam forged rods, King bearings, Elring HG, and yes...I went with new OEM stock head bolts. I figured that at 575-ish hp, the stock bolts should be fine.

Thanks for the extra information I'm excited to watch your re-build progress. I saw your other post asking about head gaskets, it will be interesting to see what knowledge people will share.

 

[IQraceworks]

Well, my Mahle coated forged pistons showed up today (shout out to CSPRacing for an awesome price ($908) and crazy fast shipping (got them in two days)). I measured them all up with my mic, and they are all +/- .0001" of each other as for as diameter goes. After measuring all of the cylinder bores, I'm going to have a .0025" piston to cylinder wall clearance...which is about perfect according to Mahle.

I think when this is all said and done...I'm going to start a post with all the N54 engine build info in one place. There is lots of great information out there on builing N54's from lots of smart people, but you really have to search for it. Hopefully I can put all the info in and engine build post and make it easier for other DIY'ers to find.

 

[IQraceworks]

Spent some time last night getting the block prepped, and file-fitting the piston rings. I went with .020" gap on the 1st ring, .022" on the second, and then left the oil rings how they came out of the box. I didn't have to file off much...the Mahle rings already came gapped pretty big. Just waiting for my Manley forged rods to show up....

 

[IQraceworks]

My rods finally showed up. These things are nice! All within 1.5 grams of each other.

 

[IQraceworks]

Well, a little bit of an update. I got the rotating assembly all put together. After going back and forth for weeks....finding all kinds of forums posts about studs, getting info from all kinds of smart guys (engine builders) that have experience with this platform, and hearing everything from "600hp is fine for stock bolts..even 700hp is fine" to ...."you definitely need head studs if you want to keep the head from lifting..a closed deck would be smart too"...and everything in between, I finally decided to roll the dice and just use the new OEM head bolts I had from FCP Euro. This is a play car...not a daily driver. I figure it's a "research project" :lol:

So....to give the OEM head bolts the best chance of holding the head on, I did a few different things.

1. I ran a tap down all of the head bolt holes. M11x1.5 for the 11mm main head bolts, and M9x1.25 for the four 9mm bolts on the corners of the head. Got them as clean as I could.

2. I sanded the bottom of the washers with 60grit sandpaper, to keep them from rotating where they seat against the head (ARP recommends to do this with all of their studs). This helps to give a more consistent torque reading.

3. I used ARP Ultra-Torque lube on the bolt threads and top sides of the washers, to make things as slick as possible and reduce the thread friction for that first 30nm (22ft/lbs)...that's the only time torque actually comes into play. After that, it's all angles of rotation.

4. Did the initial 22ft/lbs of torque on all of the bolts to seat and compress the head gasket (Elring OEM MLS gasket), and then backed them all off again, and re-torqued them all to 22ft/lbs. I was able to get quite a bit of extra rotation on the bolts after seating the head gasket the first time.

5. After about 30min, I checked all the bolts again, I was able to get another 1/4 to 1/2 turn on all of the bolts in order to hit that 22ft/lbs mark. (red paint) I'm assuming this was from letting the gasket compress some more.

After that, I went ahead and followed the BMW spec and twisted them all another 90deg (yellow paint), then did the 11mm bolts another 90deg (blue paint), and then finally did all of the bolts an additional 45deg (green paint).

I figure that if it lifts the head at 600hp.....then people can use this as a case study (of what...or what not to do) The block is flat and clean, the head is flat and clean....There was nothing else that could have been done to replicate the factory torque specs or torque sequence. I can't think of a single thing I could have done different to insure it was assembled correctly.

Next step...install the cams...

 

[r0nd3L]

Nice work! Just curious if you removed the crankshaft to hone and change the main bearings?

 

[IQraceworks]

Nice work! Just curious if you removed the crankshaft to hone and change the main bearings?

I told myself when I started pulling it apart that if the rod bearings looked worn, then I was going to dive into the crank bearings. The rod bearings, looked almost new......and since I've never, ever heard of an N54 with crank bearing issues, I made the call to save the $500+ in bearings and bolts, and hassle of splitting the block and having to reseal everythign back up again.....to just leave the crank bearings alone.

If this was a full out race motor, or a motor that I was going to be sinking a ton of money into....I would have spend the extra time and money, but this is more of a "repair, but with better parts". Who knows, maybe it will end up biting me in the butt....but I think it should be fine. I put money into the motor where it needed it (pistons/rods/timing chain/guides/crank hub).

 

[r0nd3L]

I told myself when I started pulling it apart that if the rod bearings looked worn, then I was going to dive into the crank bearings. The rod bearings, looked almost new......and since I've never, ever heard of an N54 with crank bearing issues, I made the call to save the $500+ in bearings and bolts, and hassle of splitting the block and having to reseal everythign back up again.....to just leave the crank bearings alone.

If this was a full out race motor, or a motor that I was going to be sinking a ton of money into....I would have spend the extra time and money, but this is more of a "repair, but with better parts". Who knows, maybe it will end up biting me in the butt....but I think it should be fine. I put money into the motor where it needed it (pistons/rods/timing chain/guides/crank hub).

Thanks for the response. Completely understand! I have done something similar to resolve an issue on a poorly built/broken-in N54 to rehone the cylinders and set new rings in order to resolve excessive oil sneaking past the rings.

I have another spare nice condition N54 on which I've been thinking to follow your approach and install new rods/pistons, refreshed head, but leave crankshaft/bed plate as-is. I'm super glad I saw this and are not the only crazy one.

In your photos it looked like the cylinder walls were fresh? What was the process for that to ensure no contamination?

 

[IQraceworks]

Thanks for the response. Completely understand! I have done something similar to resolve an issue on a poorly built/broken-in N54 to rehone the cylinders and set new rings in order to resolve excessive oil sneaking past the rings.

I have another spare nice condition N54 on which I've been thinking to follow your approach and install new rods/pistons, refreshed head, but leave crankshaft/bed plate as-is. I'm super glad I saw this and are not the only crazy one.

In your photos it looked like the cylinder walls were fresh? What was the process for that to ensure no contamination?

I went ahead and used a 220g Flex-Hone on the cylinders.....with the block upside down so any contamination would stay off of the crank journals. I've used those flex hones on everything from ATV/Birtbike engines, marine Big Blocks, SBC drag motors, to LS motors, and for just breaking the glaze on the cylinder walls and getting a proper cross-hatch pattern on the cylinders, they work great! It takes a little practice to get the angles on the cross-hatch right, but it's not rocket science.

After I honed the cylidners, I rotated the block back up....washed/wiped anything off of the cylinders and crank journals, blew it all off with compressed air, and called it a day. I'm a stickler for keeping things clean....so this was kind of a challange, but if you are careful, and do it right...honeing the cylidners like that works great. I've seen some pretty nasty hone jobs from "good" machine shops......so I'd rather do it myself, and they turned out great.

 

[r0nd3L]

I went ahead and used a 220g Flex-Hone on the cylinders.....with the block upside down so any contamination would stay off of the crank journals. I've used those flex hones on everything from ATV/Birtbike engines, marine Big Blocks, SBC drag motors, to LS motors, and for just breaking the glaze on the cylinder walls and getting a proper cross-hatch pattern on the cylinders, they work great! It takes a little practice to get the angles on the cross-hatch right, but it's not rocket science.

After I honed the cylidners, I rotated the block back up....washed/wiped anything off of the cylinders and crank journals, blew it all off with compressed air, and called it a day. I'm a stickler for keeping things clean....so this was kind of a challange, but if you are cafeule, and do it right...honeing the cylidners like that works great.

Awesome, thank you! I did the same with Flex Hone on the N54 I mentioned. Glad I'm not the only crazie out there!

 

[IQraceworks]

Awesome, thank you! I did the same with Flex Hone on the N54 I mentioned. Glad I'm not the only crazie out there!

Yep...as long as you keep things clean, there are all kinds of different ways to "skin the cat".

 

[r0nd3L]

Yep...as long as you keep things clean, there are all kinds of different ways to "skin the cat".

Agreed! Please keep us updated on the progress of this project!

 

[IQraceworks]

Got the kiddo put to bed early, and was able to sneak out to the shop to do some more assembly work on the motor. Got the lifters and cams in. Next step is to install the new timing chain and guides, and the new "updated" crank hub. Didn't feel like spending $1k for the pinned or splined crank hub option.

The "updated" BMW crank hub for under $200 sounded like a much more sane option...especially since I'm not going to be making crazy HP, and I'm running an auto trans..not a DCT or manual....which it seems causes the most spun crank hubs.


Pro Tip....if you want a quick and easy way to check and calibrate your torque wrenches, get one of those digital luggage scales and use it to check/calibrate your torque wrench. Plenty of good youtube videos showing step by step process. It's easy.

 

[SLOWESTN54]

Ian I’m curious about the head gasket choice with the head bolts. That head gaskets known to fail around 600. It’s worse than oem. Pairing that with oem head bolts sounds like a recipe for disaster. You should really switch it out

 

[Jern54]

While the engine is opened I deff would replace the timing chain guide and all that stuff.

 

[SlowE93]

Ian I’m curious about the head gasket choice with the head bolts. That head gaskets known to fail around 600. It’s worse than oem. Pairing that with oem head bolts sounds like a recipe for disaster. You should really switch it out

So it should handle 575 all day long ?

 

[IQraceworks]

While the engine is opened I deff would replace the timing chain guide and all that stuff.

Yep, that's the plan. I figured why not.......the chain and guides have around 100K miles and 17yrs of age on them. And since I'm pulling the crank hub off anyways, it just made since to replace it.

 

[SlowE93]

Ian I’m curious about the head gasket choice with the head bolts. That head gaskets known to fail around 600. It’s worse than oem. Pairing that with oem head bolts sounds like a recipe for disaster. You should really switch it out

Forget the head gasket. What type of engineer runs a N54 with no oil cooler ?????

 

[JohnDaviz]

Forget the head gasket. What type of engineer runs a N54 with no oil cooler ?????

I know! IQ guy does. And then he even runs an MLS gasket with stock bolts which are known to not work that great but the engineer crowd he asked tells to go that route.