Will a BP4W head on an NA8 pass visual inspection?

[mx54life]

I saw this unclaimed 99 head sitting in a machine shop. I was wondering if I swap this on my 94, will it pass visual inspection. Being in Cali sucks when it comes to upgrade. Thanks in advance.

[druz]

All depends on the smog tech. I passed 3 times with a 94 BP in my 91. The 99 head has a few more differences like the IM and EGR, will your tech notice? Usually no if eveything else looks stock.

[Rogue]

Im putting one on a 96M right now, and using the '96 intake so it will visually stock.
a bit of modification to the intake, but i doubt even a Miataphile will notice.
You should have the head skimmed to boost the 94s compression as well.

[— Willywongka —]

I am eventually swapping my head with a 99, so you recommend skimming the head to increase compression eh? I need to do a bit of research before I go and do it.

[mx54life]

Im putting one on a 96M right now, and using the '96 intake so it will visually stock.
a bit of modification to the intake, but i doubt even a Miataphile will notice.
You should have the head skimmed to boost the 94s compression as well.

Thanks good to know. So what power gains are we looking at this mod?

[etikoner]

Just reuse everything else from the BP head (CAS, VC) and you'll need the BP4W specific intake manifold as well.

Shaving the head a bit will give you some added compression. Should give the car some added oomph but not sure how many HP's....

[Rogue]

a bit of modification to the intake

1996 intake modified Like this…...
OTC_intake_manifold.jpg
mine is drilled and port matched, but still need to have the extension tigged.
I'm actually rebuilding a 95.5 BP that has the later pistons, and with a nice shave on the head should get close to 9.5:1.
Good enough for my wires commuter.

[etikoner]

I think I read somewhere that the NA8C manifold makes more power on the 99 head.... Hmmm

[Rogue]

I think I read somewhere that the NA8C manifold makes more power on the 99 head.... Hmmm

I'd be interested to read that.

[jux]

A '94 in my possession did 135 at the wheels with a '99 head swap. Granted that also included a fabbed intake, header, and MS1, but it's a reference point.
Rogue, Rick tried modding the stock intake manifold for this swap. He ran into fitment issues with, I believe, the fuel rail not fitting, so opted for the '99 manifold. Hopefully you'll see better success.

[BoBo]

I am eventually swapping my head with a 99, so you recommend skimming the head to increase compression eh? I need to do a bit of research before I go and do it.

Don't shave too much or you will retard cam timing. If you exceed the maximum limit on the head shave you might need cam gears to advance cam timing.