Technical Lots of contradicting N54 Head Stud Info online…..who’s got the facts?

IQraceworks

Corporal
Jul 7, 2020
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07' BMW 335i
I’m in the process of doing all the research I can in order to put together a reliable package that will hold 575-600hp (I’m assuming that’s what my motor is making before it broke a ringland). Forged rods and pistons, proper ring gaps, good bearings…that’s all pretty cut and dry.

The one issue I’m running into is all of the contradicting info online regarding head studs. This is some of the stuff I’ve found online.....it’s all over the place. I don’t know what to believe.

“use new stock head bolts and you will be fine…..these motors will make 700+hp without lifting a head”

“do the ARP stud kit with the (10) 11mm studs, and the (4) 9mm studs and you will be good to go”

“don’t convert the (4) 9mm holes to 11mm unless you have a closed deck block”

“the only right way to do it is to machine the block to use all 11mm studs..just drill and tap the aluminum”

“The ARP stud kits are too short…they will pull out. They are just Chrysler 2.2 studs”

“VAC sell a custom ARP stud kit that is the correct length..use those”

“The VAC kit with the 9mm and 11mm studs and is much stronger than the oem bolts..you will crack a sleeve before you lift a head with their kit. And there is no machine work needed”

“If you aren’t using 11mmx1.5 NS300L inserts for all 14 stud holes…you are wasting your time”

“Don’t’ convert the (4) 9mm holes to 11mm ones…there isn’t enough meat on the block and they will pull out”

“ The factory bolts seal so good because they are installed by a robot at the exact same time….you will never be able to make factory bolts seal the gasket well enough if you do it at home one at a time with a torque wrench”

“OEM bolts and head gasket are more than enough for 600hp if you torque everything correctly.”

Etc, etc, etc, etc…….


What’s true….what’s not? And the main question….what do I need for a reliable head fastener setup that will hold the head to the block at 575-ish hp at 25psi boost? These cars have been around for 16 years…I’m shocked that there is still so much controversy on head studs.
 

Jern54

Sergeant
Oct 18, 2019
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E91 N54 335i
My input based on my experience so far:

On my build engine I went initially with stock head bolts.
At around 750whp the head lifted at cyl 6 next to the M9 head bolt.

Decided to order the Full M11 ARP studs from Billiam which are exactly the same from VAC and are advertised for way too much money(700 euro).
Installed the studs together with NS300L inserts from Huhn Solutions.
Since then all is fine as I made 927HP at the crank.
Coolant pressure is stable as well all the time.

FWIW I have multiple full M11 studs available.
These are the same as the ones advertised from HCR.
All studs are heat treated as well.
Thread on the block side is 55mm instead of 35mm (only) from the ARP ones.

Let me know if anyone would be interested.
Price for them is: 499 euro
 

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IQraceworks

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Thanks for the great info!!

So if I'm doing a pretty mild build (550-600hp).....do you think I would be ok with new stock head bolts? Or the 11mm+9mm stud kit? or do I have to do the fill 11mm kit and enlarge the 9mm holes? That seems like the three options I have at this point.
 
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Jern54

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Oct 18, 2019
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If all 14 threads in your block are undamaged you will be fine with stock head bolts on above listed power level.

However, advantage of the studs is you can re-use them in case you want to upgrade to a ported head for instance.
 

IQraceworks

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Jul 7, 2020
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If all 14 threads in your block are undamaged you will be fine with stock head bolts on above listed power level.

However, advantage of the studs is you can re-use them in case you want to upgrade to a ported head for instance.
Great! Honestly, I'm not plan on messing with the motor any more once I get it back together. I'm happy with the power level it's at.
 

shushikiary

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Jun 4, 2018
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A bunch of that is true, some of it is false.

I agree I would not go all 11mm without a closed deck. By the time you need 11mm studs you're pushing enough power to want a closed deck anyways, so I wouldn't do one without the other. Personally I'd say 600-650 whp and you're ok being not closed deck and stock head bolts but your ring lands are on a ticking clock, under 600 whp and you'll be fine with stock everything for a good while. Personally I would not go above 600 whp without doing forged pistons, and if I'm going to go to the work to go to forged pistons then I'm going to put a closed deck in, which means doing 11mm proper length studs and then you're good for 800 whp. Yes there is indeed a GM kit with the studs too short and if you use that kit you will likely strip the block when you try to tighten to ARP's suggested torque (Make sure you use their suggested lube and put it on the threads the nut goes on and under the nuts washer surface!).

Billiam can get the correct stud kits and its where I know most people source them from, they are indeed longer than the GM kit and give you enough thread engagement so that you don't strip the block threads. (When Ghassan did my first motor build they used the GM studs and didn't tighten them properly, then when the second shop tried to tighten them (octane enterprises) they stripped as stated, from there we found out Ghassan had used the wrong head stud kit (shorter one) and had to order the proper one, which resulted in having to replace the block as there was not enough space for a time sert where it stripped... so with new block and new proper length studs from ARP it is now working properly).
 
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shushikiary

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I should add, to technically do everything right, when replacing rings and/or pistons you need to hone the block with a torque plate, this means you need to use what ever head hold down method you are using on the torque plate, so before you can hone the block properly you need to have this all figured out. Piston to bore tolerance is greater on forged pistons as they expand more, so for example if you're going 2618 vs hypereutectic cast, the cast pistons will need 1 thou or less bore clearance, but the 2618 piston may need up to 4 thou depending on power level (forged pistons expand more than the cast ones under heat), and this won't be proper at the top of the bore without a torque plate, which is where you make your highest cylinder pressure.

So all of this is intertwined, which is why I suggest going all the way or staying mostly stock. Adding ARP studs to a stock head with no closed deck insert on hypereutectic pistons could change the top of bore clearance more than you'd like as your clamping force has gone up with no addition support on the bore. Will that blow up an engine? No not likely... but it's not ideal.
 
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IQraceworks

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@shushikiary

Great info! Thanks so much!

Yes.....at 575-ish hp, ringlands are an issue.....I broke one, and that's why the motor is coming out. From everything you said.....I guess I'm better off just putting a new stock cast piston in the motor with all new rings gaped correctly, ball hone the cylinders for the new rings, new rod bearings, new head gasket and new stock head bolts.....and run it? The motor was running great for a couple of years before the ringland broke on piston #4...so I think it was just bad luck.
 

Jern54

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Oct 18, 2019
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@shushikiary
I'm running a sleeved open deck block at 815WHP. It's doing fine for almost 20k km now. If it goes it goes and I will throw in my stock closed deck N54 which you can see above.

But that's another topic as this is about head bolts/studs.
 

shushikiary

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Jun 4, 2018
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Data... good data is not a few data points, it's a large data set to get statistical values.

Run what you guys are saying at your own risk. If you're ok with that risk tolerance... great. My advice would be not to do what Jern an Slowest are doing unless you're ok replacing a motor at any time, because every time you floor it you're rolling the dice with a higher percentage you'll get hosed than others. Glad to hear you've not rolled snake eyes yet.

If I were you IQ, knowing I've already blown ring lands at 575, I wouldn't go to all the work you are doing and put hypereutectic pistons in, it would get a forged set with stronger rods.... but my budget may be different than yours.
 

fmorelli

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Data... good data is not a few data points, it's a large data set to get statistical values.

Run what you guys are saying at your own risk. If you're ok with that risk tolerance... great. My advice would be not to do what Jern an Slowest are doing unless you're ok replacing a motor at any time, because every time you floor it you're rolling the dice with a higher percentage you'll get hosed than others. Glad to hear you've not rolled snake eyes yet.

If I were you IQ, knowing I've already blown ring lands at 575, I wouldn't go to all the work you are doing and put hypereutectic pistons in, it would get a forged set with stronger rods.... but my budget may be different than yours.
The problem with the last statement - if you don't have the budget to build it, you don't have the budget to blow it.
 

Jern54

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If you are using OEM Cast pistons keep it below 500ish hp
Especially if you are running it on pump fuel and on twins.

Is it your daily car?
 

IQraceworks

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If you are using OEM Cast pistons keep it below 500ish hp
Especially if you are running it on pump fuel and on twins.

Is it your daily car?
Nope, not my daily car....just my toy. My 93 tune is around 500-ish hp, but my E40 tune is probably 575 or more. What's it take to get a full weight 335i to run 10.90's at 128mph....because that's what it's running (before it cracked a ring land).

So forged pistons are rods are mandatory at 575-ish hp? I was hoping I didn't need to drop $2K on pistons and rods...but I also don't want to have to pull the motor out again and do all of these a second time.

See....this is the problem I'm running into. Even in this post, lost of contradicting info. I'm thinking that just for insurnace purposses....forged rods and pistons might not be a bad idea. According to Mahle, I can just ball hone the cylinders, and drop their forged pistons in......they are machined for the correct tollecrences for the factory 84mm bore (I would or coarse still mic everyting out and double check).
 

SLOWESTN54

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Data... good data is not a few data points, it's a large data set to get statistical values.

Run what you guys are saying at your own risk. If you're ok with that risk tolerance... great. My advice would be not to do what Jern an Slowest are doing unless you're ok replacing a motor at any time, because every time you floor it you're rolling the dice with a higher percentage you'll get hosed than others. Glad to hear you've not rolled snake eyes yet.

If I were you IQ, knowing I've already blown ring lands at 575, I wouldn't go to all the work you are doing and put hypereutectic pistons in, it would get a forged set with stronger rods.... but my budget may be different than yours.
Only reason i didn't go with sleeves, or a Closed deck conversion was, in Canada their aren't many shops that i know who offer it for N54's. And shipping to the states, plus duties on top simply wasn't worth it at the time. Hence i built the bottom end to hold as best i could.
 

IQraceworks

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Jul 7, 2020
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Ball hone is for riding mowers :)
I've seen quite a few turbo LS's that have had ball hones used on them.....and made big power. If you are just breaking the glaze on the cylinder walls in order to seat new rings, they actually work really well.....at least, that's been my experience.
 

rev210

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If you are using OEM Cast pistons keep it below 500ish hp
Especially if you are running it on pump fuel and on twins.

Is it your daily car?
Agree about the pump fuel for sure. You can push stock gear further if you regap the rings (open them up), this is a general rule for power vs gap . That's where most of the issue is for the ringlands on stockers but, if the pistons are comming out for that it begs the question.