rosaatomica

So here we go. I've been hanging out on this forum for a couple of years now and am just starting to post. I am in the process of building a 1.8 swapped '91. 95 block with a 99 head. The block has already been machined and I've decided to go with; Supertech 8.6:1 84mm pistons and Wiseco XX rings, ARP head studs and main studs, ACL bearings with standard clearances. The head was originally going to be the matching head with just Volvo vs855 springs.

I decided to go a different route and now have a '99 head and square top intake. I have MMD SUB lifters for it from Miataroadster (still no shims as I've read that comes later once the machining is being taken care), the Supertech double springs kit(74lbs), Supertech intake valves 33mm standard (part number MAIVN -1204, which i believe are the black nitride hi-flow), Supertech exhaust valves 29mm + 0.6 longer (part number MAEVI - 1206 which are the inconel ones). Oh and stock cams as well. No porting or polishing.

The head is currently at a machine shop in California. I'm not in California but my uncle is and he happens to be close to a machine shop. The problem is I'm not sure if the machine shop is for the task of assembling the head for me. The machinist tells me he will have to take too much off the valves and the lifters will fall off. I'm under the impression that he doesn't exactly build a lot of miata/race/upgraded heads and perhaps I should find a machinist that knows exactly how to build a miata engine. Is there anyone in the LA area, hopefully around the valley, that I should contact? I'm hoping the machining wont cost me another arm and a leg as these parts have already set me back a bit, but I did choose to go for a well built engine so that's my fault at this point LOL. Either way I care more so about getting this done right the first time because I cannot afford to blow up this engine. I try my best to search the forums and do my research about all this engine building stuff but perhaps some of you could point me in the right direction.

technicalninja

The single most helpful area for power is in the head casting. The throat beneath the valve seat can be worth 5-10% more flow. More flow improvements than the valves themselves. This area needs to be worked BEFORE the valve job is done.
This area needs to be carefully smoothed out without undercutting beneath the seat. The short side radius is the more important area and on the intake port it is damn tight (hard to work properly).

I've recently worked on an Uber head for a forum member and saw some things I didn't like.
The Supertech valves are NO LONGER 0.6 mm longer than stock as all of the vendors state. This makes the upgrade to SUB buckets CRITICAL. You cannot "tip" the valves to adjust clearance more than .005"
The Inconel exhaust are BAD ASSED and even with the stock length issue worth it.
I will not use Supertech intakes on anything I build. This head with less than 10 hours on it had significant valve face recession. Even with the super wide (.060-.065) patterns I sent it back with appears to be continuing to wear improperly.
The Jurys still out on this head but I wanted to chuck the intakes and go with a different manufacture. Time was of the essence so the too short Supertechs stayed in this head.
We need the additional 0.6mm longer valves for "working area" especially when adding aftermarket camshafts (smaller base circle) and my customer went to the trouble of contacting Supertech to find out they changed the length to "stock" a while back and didn't tell anyone...
Had they been available we would have upgraded to SuperTech Inconel intakes which FM still shows on their website. They only have 6 left and no more will be available...

The Mazda SUB buckets we used had an internal ridge at he bottom that contacted the Supertech doubles. I machined this ridge OUT of each bucket. The stock Mazda SOB buckets did not have this ridge at all.
When I do this again I will either use the stock stuff and accept a lower redline OR look into the later Zetech (FORD) stuff that might be applicable using NO shims at all (bucket is the shim).
I haven't done "due diligence" on this mod yet and probably will not as the increase of 500-1000 RPM doesn't seem to be worth it IMO. Stock stuff will do 7K easily and if you're going over 8K you really need a bunch of expensive lower end stuff (like a billet crank $$$$)
If the shims you are using fit onto the buckets themselves the stem length above the keeper doesn't matter.
If the shims you are using fit over the valve tip (Mazda style) ANY machining of the stem can create disaster.
I had 0.013" removed from 1 of the intakes which allowed the shim to CONTACT the keepers...
I needed either longer stems (0.6mm would have been PERFECT!) or modified shims. The shims were modified.
The customer found (very difficult) and had a new set of intakes sent to me overnight at which point I found that they were stock length anyway,
Damn disappointing...
Had I "let it go" the customer most likely would have dislodged the keepers at speed and dropped a valve...
This was a SuperMiata CNC head with ALL of the very best top end stuff in it. Customer had 6 grand plus into head BEFORE he sent it to me.

My "recipe" for a 99 head would be as follows.
Manley 1mm oversize intakes.
Supertech 1mm oversize Inconel exhausts.
The Volvo springs OR the Supertech heavy doubles.
Normal Mazda buckets with shims on top (much much easier to adjust valve clearance) and a redline no higher than 7500.
Or shim-less buckets with a higher redline (and a more expensive bottom end).
The MSM intake cam. slightly more duration and lift over stock and inexpensive.
Careful port "profiling" not really ported and made bigger, just all sharp spots smoothed out. Work concentrated 1/2" either side of valve seats.
Intakes left rough but exhaust "smooth as a baby's ***"
Same "smoothing" in the combustion chamber.
Ceramic coating of the exhaust port and maybe combustion chamber.
Ceramic coating of the exhaust valve (might not be needed with Inconel) and the chamber side of the intake valve.

Street car I'd go cheap, Volvo springs and stock buckets.
If I REALLY had a reason for extended use above 7500 RPM I might spec out the more expensive crap but I'd REALLY REALLY think about changing platforms and staring with a more robust engine in the first place (Honda stuff would be my first choice).
The single most important thing to have in a performance engine is a good flowing head...
The Honda (when worked properly) can flow nearly DOUBLE what a Mazda head can flow (even a worked one).

My 2 cents, hope it helps

andyfloyd

Here is what I did for my head. I kept it simple and its made just over 400whp on a GTX2860. I did not touch the ports or the seat transitions like Ninja was stating. You can do this for free hp i just didnt want to mess with it bc I knew I didnt need to to reach my goal. I have all stock in/ex valves but they are backcut which only cost me 40 bucks when the valve job was done which is a radius valve job. I used regular lifters and a BP5A intake cam and the stock bp4w ex cam. Supertech 74lb doubles and ti retainers. Thats really all I did and now the car is making right over 400 and peaking at 7000rpm. You dont really need to get cute with it.

technicalninja

Bingo! both of those mods are paramount!
Where did you get a "radius" valve job done?
Did I miss pictures of this in your thread?
I would LOVE to see a picture of your seats without the valves in them,
How wide was the "seat" (contact point) on both intake and exhaust?
What did that cost?

Now, if you had the very best valve job done (IMO) and you didn't smooth it into the port properly I believe you left more than 5% total power (20 hp minimum for you!) at the table for FREE
Just time with a die grinder and not that much time if you're just working the transitions as I suggest.
How HARD did you work for that last 20hp you needed for your goal?
Seemed hard to me...
It might have been "there" from the start.
It's probably waiting for you right now for no more cost than a HG and stem seals...

The last picture I remember of your ports had significant excess material (lumpys) at the port to seat interface. We WANT excess material for proper flaring. When the seat is undercut is when you have problems. Undercut requires either larger valves and a larger throat size or adding material to the port wall.
I avoid the '"adding material" at all cost. I'd look for a better core before adding anything to a port, especially an intake port. I believe any epoxy- magic putty you put in an intake port will sooner or later become a foreign object lodged in a piston crown at some point down the road.

I'm more prone to use the stock valves as well but the original poster stated he was changing valves anyway. If you are PAYING for high end valves and a high end valve job it is silly to stay stock size.
I'd not use a 2mm oversized valve UNLESS I was building a "PatMX5" motor but the 1mm oversize gives you a little more "wiggle room" to better flare your transitions and doesn't cost much more than the same valve in stock size.

Now a Ninja "cheap head" would reuse all of the stock parts EXCEPT the valve springs and they would be the Volvo springs below 18 psi boost level.
I'd do a flat top intake and Skunk junk before I added the MSM cam which I would want as well (2-3% total power maybe).
I'd still massage the crap out of the transitions on this head even with the stock parts.
I'd back cut the valves and I'd KILL to get a true radius valve job...
I'd run the valve adjustment at 6 on the intake and 10 on the exhaust with stock or MSM cam.
I'd add adjustable cam gears before going to oversized valves and then play with cam timing on a dyno.
I'd add a coolant re-route from SM.
So before taking the high performance valve route I'd have already done the "supporting" mods first.

I will be doing a thread on a VVT head I will be building "on the cheap" for my car and I'll show what I would do then.
Right now in the Automotive AC world is the single busiest time and it will be cooler here in Texas before I do this.

With the exception of high compression and large valve overlap anything that helps a NA motor make more power will also help a FI motor in about the same PERCENTAGE!
So 5% will stay 5% usually... On an NA Miata a mod that will net 5 hp will net 20 plus on a serious boosted car like yours Andy.

And one last point. I've never seen proper bowl, port transition work be worth LESS than 5% and often it's worth more...
On anything!
Just changing to high performance valves leaving the port completely stock (no oversize) will be damn hard to see on a dyno.
Although they may survive better in your application just adding valves will not change power production very much.
Taking stock valves, back cutting them and then having a RADIUS VALVE JOB done will show up on the dyno
Adding proper port work will make it shine even brighter...

andyfloyd

Yea I mean you are right I could have easily worked over those areas and picked up big gains. Laziness took over lol. I could be mistaken it might just be a 3 angle but I know my Machinist can do both. I'll attach a picture of one of the valves from my cracked head bc they are the same as what I'm running in my car now.

Newaza

Yikes!!!! 6k in the head before rework? I would have a heart attack at just the thought of spending that amount on a miata head...

rosaatomica

ok so i've decided to return those Supertech intake valves and am now searching for Manley intakes. But the thing you said about having the Mazda SUBs machined out has me worried. is that something i should let the machinist be aware of? is there any machinist in the LA area that would know exactly how to assemble this head for me?