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Considering getting a spare NB head to build up to put on the NA.

Now I already got some shiny tighe cams for the NA, so what i was wondering, is this.

Is it possible to swap over the NA cams and HLAs into an NB head? I know the 2001+ heads don't have any oil feeds for the HLAs, but what about the earlier ones?

And I know that i would be better off getting new cams for the NB instead, but I want to save money where i can, and I don't think the HLAs are that bad!

Or should I just get a bit of porting done on the NA head?

I'd see if anyone in your local club is interested in buying your NA head, let them drive the car with it in to see the difference and so they know the valve guides/seals etc aren't leaking.

Once they agree to buy it then use that cash to get some cams for the NB head.

daffyflyer wrote:Considering getting a spare NB head to build up to put on the NA.

Now I already got some shiny tighe cams for the NA, so what i was wondering, is this.

Is it possible to swap over the NA cams and HLAs into an NB head? I know the 2001+ heads don't have any oil feeds for the HLAs, but what about the earlier ones?

And I know that i would be better off getting new cams for the NB instead, but I want to save money where i can, and I don't think the HLAs are that bad!

daffyflyer wrote:Or should I just get a bit of porting done on the NA head?

as you know porting's not cheap & i don't believe you'll replicate the gains of the wide intake/ exhaust port angle of the NB8A head, so it might not be money well spent.

also if you're looking to economise, an nb8a head is usually going to be expensive, that's if you can find one when you want it.

ultimately you won't be maximising all the benefits of an nb8a head, but here's a couple of photos of bp4w (nb8a) head showing intake & exhaust side with an oil feed visible near the top on the outside of each lifter boss.

here's a photo of a bp05 (na8) head - what can be seen looks the same, but can't vouch for oil feeds that may be further down in the boss.

Yeah, kinda sounds like a bit much effort

OK -http://www.targamiata.com/diary.php?UID=143 seems to confirm you can run old cams and HLAs in a nb head, and they clearly hold up not too bad in a higher rev motor considering what he did.

useful to confirm - but if you get an nb8a head, cams for solid lifters would maximise gains as okibi suggested. of course, you then have to factor in the cost of re-shimming (x16) to achieve correct cam to lifter clearance. but i think this is a case of go all the way or stay with the na8 head, unless you can get a nb8a head easily & cheaply.

The bolt pattern for the intake (and maybe) exhaust manifolds are different between the NA8 and NB8 head, so factoring costs for modifying or swaping manifolds comes into the mix too.

project.r.racing wrote:The bolt pattern for the intake (and maybe) exhaust manifolds are different between the NA8 and NB8 head, so factoring costs for modifying or swaping manifolds comes into the mix too.

The guys on Miata.net say the exhaust manifold should be interchangable.


Planing on building a custom ITB manifold (out of a hacked up nb manifold) anyway.

All comes down to if i can get a head cheaply really, sounds as if they are quite pricey though yes?

daffyflyer wrote:The guys on Miata.net say the exhaust manifold should be interchangable.

correct

daffyflyer wrote:All comes down to if i can get a head cheaply really, sounds as if they are quite pricey though yes?

Oh yeah - you can modify an na8 intake manifold for nb8a head, but not optimal, & you'll also need an nb8a fuel rail.

Have you checked with Tighe to make sure the cams you have aren't suitable for solids? Depending on the grind, sometimes the ramps are OK for either - they may not be but would be a worth a phone call to confirm.

Thanks CT, whenever i see you have posted in my thread i know there will be some excellent info

The Tighe website says they are for hydraulic but will give them a call and confirm.


Im guessing if you can run the with solids they would end up being a bit more wild? (im assuming some of the lift of cams is used up squashing the lifters?)