Can someone explain to me why an N53 head is recommended for HP 800s? Compression?

Bmurata90

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Nov 28, 2019
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It's either I go single with a 6466 and dump my twin setup parts or go with Hydra 650s or 800 v2s. I love the love end torque that twins provide and will be building my motor soon either way to make sure it's bulletproof, but if someone could kindly explain to me why a N53 head is recommended? I have theories and read up on some contradicting things, so I'd like some more "knowledgeable" people to explain this to me.

Omar? Maybe you can chime in?
 

ShocknAwe

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Removes flow restriction that is the N54 head. Bit of an exaggeration but imagine making same power on 16psi as you would on 30.

dont need the N53 head, can always port the N54 head plus minus upsizing valves.
 
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SLOWESTN54

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Removes flow restriction that is the N54 head. Bit of an exaggeration but imagine making same power on 16psi as you would on 30.

dont need the N53 head, can always port the N54 head plus minus upsizing valves.
Are you sure the difference is that crazy
 

Bmurata90

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Nov 28, 2019
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Removes flow restriction that is the N54 head. Bit of an exaggeration but imagine making same power on 16psi as you would on 30.

dont need the N53 head, can always port the N54 head plus minus upsizing valves.
Will probably just port it and do the valves since I'll be either rebuilding my motor or buying a used one to build.
 

Bmurata90

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Nov 28, 2019
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Removes flow restriction that is the N54 head. Bit of an exaggeration but imagine making same power on 16psi as you would on 30.

dont need the N53 head, can always port the N54 head plus minus upsizing valves.
I know you said you were exaggerating, but approx how much lower would the PSI be compare to 30?
 

ShocknAwe

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Can't make a finite statement like that since you'd need back to back tests which we don't have.

I was trying to make a point, definitely an exaggeration.

My setup (not my car) made 625 on around 18 psi (on pump). Looking around quick seems it generally requires around 25psi with a single or big twins to achieve that on the stock head. Comparing to stock turbos my setup allegedly made similar power at 8psi (stock boost level) as a FBO car maxed out, both on pump. Not sure if this can be done on pump without a high flow head, or if it's the Schrick cams, or what.

I'm not going to get involved in a buy this not that discussion though. At the end of the day it's just air flow and combustion. To oversimplify I decided lower numbers made me feel more comfortable with longevity than higher numbers.
 

SlowE93

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Can't make a finite statement like that since you'd need back to back tests which we don't have.

I was trying to make a point, definitely an exaggeration.

My setup (not my car) made 625 on around 18 psi (on pump). Looking around quick seems it generally requires around 25psi with a single or big twins to achieve that on the stock head. Comparing to stock turbos my setup allegedly made similar power at 8psi (stock boost level) as a FBO car maxed out, both on pump. Not sure if this can be done on pump without a high flow head, or if it's the Schrick cams, or what.

I'm not going to get involved in a buy this not that discussion though. At the end of the day it's just air flow and combustion. To oversimplify I decided lower numbers made me feel more comfortable with longevity than higher numbers.
Don't send > send it



This should cover it.
 
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jzx_andy

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I'd suss out the overall cost of porting the n54 head vs fitting a n53 head + manifold flange/s, and go from there. I think you would want cams in either case though, so consider the cost of that. If the appetite to spend real money (i.e. headwork + cams + engine build + new turbo setup) is there, you can't really go wrong with either option. Both flow a lot more than an untouched n54 head.

Doing the usual 600-800hp built n54 street car thing doesn't usually justify the cost/hassle of headwork in my view. While the head has well known shortcomings and making the n54 breathe better and feel more like a race engine is awesome, I don't believe fixing shortcomings with the head will add substantailly to the overall reliability of a built n54 engine, given the typical issues are usually found elsewhere (i.e. way too many shoddy people building/tuning n54's, cooling systems not adequate for intended use, factory di system, open deck block with insufficient cooling for the rear cylinders, etc). It is still a 15yo bmw engine that has suffered with issues and wasn't designed to make more than ~65hp/cyl.

But if you're in so deep on the build that you're willing to try make absolutely everything work better or more reliably, or you're chasing every ounce of potential, then you might as well. Lol.
 

surge89

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Feb 27, 2024
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Theres a company called nexys making a port injection conversion kit which means you could go n52 head

Only issue I see with the n53 and n52 heads is the bore size is different by 1mm not sure how critical this is, I know you can always bore your block but then you'd probably want to build the engine and it turns in to another can of worms maybe someone more knowledgeable can chime in
 

mikeseli

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Theres a company called nexys making a port injection conversion kit which means you could go n52 head

Only issue I see with the n53 and n52 heads is the bore size is different by 1mm not sure how critical this is, I know you can always bore your block but then you'd probably want to build the engine and it turns in to another can of worms maybe someone more knowledgeable can chime in
A 1mm increase in diameter on the head side is negligible in most of the cases. What matters in circumstances where the head bore is slightly larger is that the gasket matches and is able to seal and the final static compression ratio is verified. The N53 head on a N54 block works.
 
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island road

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Theres a company called nexys making a port injection conversion kit which means you could go n52 head

Only issue I see with the n53 and n52 heads is the bore size is different by 1mm not sure how critical this is, I know you can always bore your block but then you'd probably want to build the engine and it turns in to another can of worms maybe someone more knowledgeable can chime in

There is more to do to the N52 than there would be to N53. In addition to opening up the coolant passages / welding ones you don't need then decking. The N52 head also requires milling the valvetronic bridge and fitting an intake cam ledge with some proper cams as the N52 never came with valvetronic. If this was not the case the N52 head would be perfect seeing as it already has fuel injector ports "No DI" and then no need for an upgraded intake manifold.
 
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surge89

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Feb 27, 2024
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You mean the N54 never came with valvetronic ?
Why deck the head, to increase compression ? A lot of us pump gas guys wouldn't mind lower compression unless you'd end up under 9 to 1
I don't know about the cam situation haven't looked in to it that far just saw this video fun starts around 9 minutes


The coolant and passageways seem like less work than the n53 but the valvetronic and cams could make it unfeasible, also the n52 and n53 share the same exhaust manifold that's different than the n54 .
I'd also be concerned about the piston design N54s are designed for DI with a cylindrical hole in the center again not sure what a factor this may be.

Edit: It would be cool if it was possible to incorporate valvetronic in the N54 would it be possible ? Also the pistons valve reliefs would have to be widened for the bigger valves lol
 

island road

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You mean the N54 never came with valvetronic ?
Why deck the head, to increase compression ? A lot of us pump gas guys wouldn't mind lower compression unless you'd end up under 9 to 1
I don't know about the cam situation haven't looked in to it that far just saw this video fun starts around 9 minutes


The coolant and passageways seem like less work than the n53 but the valvetronic and cams could make it unfeasible, also the n52 and n53 share the same exhaust manifold that's different than the n54 .
I'd also be concerned about the piston design N54s are designed for DI with a cylindrical hole in the center again not sure what a factor this may be.

Edit: It would be cool if it was possible to incorporate valvetronic in the N54 would it be possible ? Also the pistons valve reliefs would have to be widened for the bigger valves lol


Opps got that backwards N52 has Valvetronic so that would need to be milled and then intake cam ledge installed with correct Cams.

As for the decking of the block, the N53 has different coolant passages. So in order to get the N53 work you open up the coolant passages to match the N54 head gasket and weld up the ones or shape that ones that don't align to the head gasket. I am not 100% sure about the head on the N52 but you would need to do the same thing and after welding you always need to deck the block.

Basically it's less work to fit the N53 head to the N54, not only that its been tested and working and have good benefits even to a ported N54 head. You can take a complete N53 head, do the mods to make it fit and use all the same cams "From My understanding" as long as you tune for it.

Of course taking into consideration your exhaust ports are going to be different and you accommodate for this.
 

ShocknAwe

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Basically it's less work to fit the N53 head to the N54, not only that its been tested and working and have good benefits even to a ported N54 head. You can take a complete N53 head, do the mods to make it fit and use all the same cams "From My understanding" as long as you tune for it.

Of course taking into consideration your exhaust ports are going to be different and you accommodate for this.

This is correct. I'd rather N53 head and plug DI if that's the plan. Not that I'm unbiased, but I try to be objective.
 

island road

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Can you link those threads? I can't seem to find any other than this one and an old for sale post. I messaged Hydra but the greedy bastards only want to sell their kit not share any info.

This whole thread - worth the read start to finish.