roystondrake

So i am in the proccess of building an engine for my 92. I have a 94 complete engine and im trying to get a gameplan together for this build (my first miata build) and i see in most big boost applications most people choose to go with the vvt head. I guess im wondering why go through all the hassle? Ive read that this head allows for better flow, but why not port the head i have? Please excuse my ignorance, I come from a performance machine shop that deals with mostly sbc and bbc builds for race applications.

Ted75zcar

iTrader: (2)

Intake port angle is improved starting with the NB1 bp4w and continuing through the nb2 vvt head. VVT adds variable intake valve timing.

psyber_0ptix

iTrader: (4)

Also to add to the above, vvt heads are seemingly more abundant since the Bp4w was on the miata for fewer years.

I bought a Bp4w head for $600 and built it. Then I bought a vvt head for $300 to replace it when that motor let up.

Only because of availability. It's only one extra wire to run and all the literature is available in the vvt megathread in terms of values and tables.

z31maniac

Read?

Savington

iTrader: (31)

VVT heads are still available and inexpensive because the prevailing M.net wisdom for years was that VVT wasn't worth it. Then a few early pioneers (y8s and several others) proved that it very much was worth it, and it's slowly caught on, other than a few M.net stuck-in-the-90s posters who are too stupid to like good things.

Your BP05 head with a full race P&P job will flow about as much as a stock 99-05 head (port castings are the same, 01-05 just adds the VVT mechanisms). You can spend $300 on a serviceable 99-05 casting or $1500 paying a competent porter to get the same flow numbers out of your existing head, your choice. The VVT heads will make more low-end torque at the expense of a couple horsepower above 6500rpm, which is a worthy trade in every conceivable application.

The "hassle" is picking an ECU that can do it (there are half a dozen of them, plus VVTuner if you manage to get one that doesn't), hooking up two wires, and tuning the targets.

chicksdigmiatas

iTrader: (11)

I got a VVT head when it was "cooler" to have a 99 head. I got it because it was 200 bucks, and the guy I bought it from was a turbo miata guy with a built engine that told me "the vvt wasn't worth the fuss, so he isn't dealing with it." I honestly really did want the 99-00 head for less of a headache, but the price was so good (99-00 heads were $500+) and I realized the VVT head had the same flow so I grabbed it. Now I'm really glad I did.

Got it resurfaced and stuck some new valves in it and never looked back. At the time, there was someone running one with a window switch, so I did that. I finally upgraded to a decent computer, so that made life better. Plus, from what I have read there is less offset (casting shift?) between the top and bottom of the VVT head.

I would suggest you get a MS3x to run it. But you can make due with just dropping the engine in there, and getting it running on the stock ECU, and also there is a VVTuner option too. All of those others suboptimal to standalone.

Why not port the one you have? Savington said it all.

psyber_0ptix

iTrader: (4)

It's crazy when people say it's more headache to run. It's an extra wire to the ecu (power grabbed from injector harness) and just plop in the established oem like settings. Any tuner will be able to figure out the rest.

If you're able to wire your own radio then VVT is trivial, especially if you're doing your own motor build /swap

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ridethecliche

iTrader: (2)

/Me

Makes mental note to look into selling NB1 head and buying VVT head this winter when swapping rodz.

cabowabo

EDIT: Pfftt nevermind.

huesmann

iTrader: (1)

Is it easier to swap a VVT head onto an NA8 block than to swap a complete VVT motor into an NA car? (Assuming you have access to both manifolds, I guess.)

Morello

VVT engine works pretty well for me.. picked my whole engine up with transmission (52k miles) for $700.

aidandj

iTrader: (5)

Exact same process.

chicksdigmiatas

iTrader: (11)

Maybe its because ive done both one too many times, but it seems just as easy to swap an engine as it is to do head swaps if youve got the tools. Opinions may vary. Things like getting stuff clean and lining things up are easier with the engine out.

Just depends which parts you have. I wouldnt crack a good engine open to swap heads, but i wouldnt pull an engine to do a head gasket either.

psyber_0ptix

iTrader: (4)

Head swap is easy peasy, if you don't need to haul the trans put and the bottom end is in good health, just clean the head gasket surface and slap the vvt head on.

roystondrake

Thank you for all the info! Im thinking ill probably go vvt. The only reason i wondered about 94 head was becuase 1. I already have it and 2. If its possible to get good flow out of the head i have i could have a coworker port it for free

shuiend

iTrader: (24)

Your coworker porting it will never be as good as a 99+ head.

Midtenn

iTrader: (15)

I don't think that running the VVT is the biggest "headache" of the swap. For some people, its finding all the additional parts needed besides the head assembly. Not as many people sell the oil tubes, solenoid, actuator, and valve cover.

chicksdigmiatas

iTrader: (11)

That's a good point, If you don't buy everything with the head, you can get into some $$$ getting all the supporting stuff. I think it cost me another $60 to get the oil line and plastic timing cover. I still got the whole head/valve cover, with solenoids for $200 though. I think it is worth the $500 or so for the superior head casting and VVT.

Morello

At that point why not just get an entire VVT engine (at likely lower miles) and sell your existing engine? Pulling the engine/trans as a unit in the miata is pretty trivial. I got $350 out of my running 150k mile NA8 engine... so the difference for a running, complete VVT motor with 52k miles (and its attached transmission) was $350, and now I have a spare trans.

chicksdigmiatas

iTrader: (11)

Mine had a ventilated block? Yeah, that's fine too. No biggie. It was worth buying all the extra stuff. Even had I paid $200 more it would have been.