The site has been over this and over this. Everyone has there own opinion.
But here it goes.

For 12 psi in a miata, You need do nothing extra. But for more horsepower some say port heads etc. etc.

This head shop said "let the turbo do all the work". Well we know that.
He was so stupid he couldn't hear me out.

Anyway, I may just run boost on stock for a while. Begi said 12 psi will give good power and dependability.
So i will run 12psi. But if I ported the heads and had valve angles. Wouldn't it flow more efficiently. More air for the same psi???

Or will it not make much differance? He said he would just have the valve angles done, That should give 15 hp on turbo. The 3 angle job is $135.00

At what psi will head work be worthy.
What do you think?

And yes, I will deffinatly be checking more head shops for there opinions.

 

On top of the gains in flow, headwork helps with spool. Worth it, IMO.

 

Read this Autospeed article on the topic. Interesting.

 

^That is an interesting article... but all his talking points are based around a naturally aspirated engine, always in vaccum. I think the article would read differently if he'd started with the premise of boost.

In any case, the $130 price quote can't include teardown and reassembly of the head. If you have him strip and reassemble the head, the price goes up dramatically... so you might want to do some homework into what it takes to do that. If he's going to do any work at all, you might as well have him do more than just the valve-angles.

But to a certain degree, I hear what your mechanic is saying. Guys have no trouble making 250whp at 12-13psi with the right turbo on this car. If you had your setup listed in your sig I would make helpful comments, but as it stands, the Begi S4 manifold and a GT2560 w/3"exhaust sounds like a good place to start before headwork if the motor is currently solid. When you blow it, then rebuild it right.

 

you need to talk to John Day in Richardson. He's made tons and tons of FI miata motors, and from the reaction of people on this forum, dirt cheap.

 

True, true.

 

If you have the head off, there's no reason to not do a little headwork.

 

First off, I would not do a multi-angle valve job on a turbo car. Cutting the seats in this way reduces the total surface-area of the contact patch between the valve and the head when closed, which in theory will decrease the cooling of the valve through the seat and into the head.

As to headwork in general such as polishing, port-matching, etc., it's a fairly basic tenet that for any given manifold pressure, a properly worked-over head will produce more power than a stock head.

In a naturally-aspirated car, you have a definite upper-limit on the manifold pressure that you can achieve, namely atmospheric. Thus, headwork is one way to overcome this limitation.

In a turbo car, assuming you have some margin for dealing with the extra heat, it's much cheaper and easier to just turn up the boost. Yes, a well ported head will make more power at 12 PSI than a stock head, but why bother when you can get essentially the same result by twisting the **** to 13 PSI?

 

Ta DA! here is my setup.
Where is that guy in richardson?

 

Turbo motors respond the same to headwork as NA motors do.

 

if you have a 94-97 just pick up a 99/00 head/intake

 

...and then get the headwork done...

- L

 

It is funny... I never found a big difference in power between my 94-97 head or the 99 head I used on my old 500+ horsepower Miata. Both were stock and would create the same HP within 1-2hp. (Which could be just due to different days etc)

 

Interesting. You are the only person to ever claim this.

 

Tod, headwork always helps, and a lot at that if done properly. End of story!

The only question is, is it worth it to you?

In your case, I think not. I don't see why you would want to drop $1000-$1500 (and yes that's how much real head work will cost) in a head if you still have a 2.5" exhaust and only pushing 12psi.
Taking a head of to just angle the vales will be as usefull as dropping the pan to do an oil change. If you're gonna build a head, build the whole thing, lighter vales, stronder retainers, stiffer springs, custom cams, adj. cam gears, bowl blending, port matching, unshrouding, etc...valve angling is not gonna even tickle your pickle.
There are so many other thing that you can do for more power for much cheaper that it just doesn't make sense to do any headwork yet.