Porting the 99/00 BP head
 

This is the same head casting from this thread.
https://www.miataturbo.net/engine-pe...pection-70069/

The customer is building for boost, and wanted some porting done.

What the stock head looks like down the runners.

https://www.miataturbo.net/attachmen...ine=1356717646

The tools used.
https://www.miataturbo.net/attachmen...ine=1356717646
No! Fae... You can not use a sawzall for this!! :fael:

Setting the head to start on the roof of the runner.
https://www.miataturbo.net/attachmen...ine=1356717646

A 50/50
https://www.miataturbo.net/attachmen...ine=1356717646

Getting the roof and divider rough into shape.
https://www.miataturbo.net/attachmen...ine=1356717646

The burrs were loading up with aluminum.
This happens with some heads, but not all.
https://www.miataturbo.net/attachmen...ine=1356717646

I added some cutting fluid to the burr, I get a cleaner cut now.
http://i261.photobucket.com/albums/i...d/IMG_1629.jpg

Roughing the bowls into shape.
https://www.miataturbo.net/attachmen...ine=1356717646

http://i261.photobucket.com/albums/i...d/IMG_1634.jpg

Smothing the bowls some
https://www.miataturbo.net/attachmen...ine=1356717646

Loving this info and pictures. Thank you.

Subscribing.

I'm working on a spare head at home now. This is inspiring to say the least.

Looking back through your older threads again, I really enjoy the new camera too.

Any chance there is a flowbench in the shop? :x:

What should I expect to pay for "some bowl work" and what are some of the cheap, easy things to do for an NA engine?

Very nice work; but why don't the manufacturers start with this shape in the first place and just leave it rough vapor honed? Castings wouldn't cost any more, would they? And look at the metal they would save.....

Glad you are enjoying them!

I am a little better set up than the avarage home DIY'er for porting. :D

You can Thank Aaron for handing me a better camera, and givin me a lesson on how to use it.!

<<<<---- Like the one in my avatar pic??? lol
Ill have to get a new base, and make an actuator.

The base I have is 4" one side and 4.250 on the other, doubfull I would get an accurate reading with it.

Ill look into Getting a proper sized base so I will be able to flow decently.

The cheap and easy would be mill the head to get the compression up.

Some bowl work would help, but the casting is so rough in the runners, they need smoothed too,

Welcome to the rabbit hole... care to fall in????

On a NA engine, I would not work the bowls as heavy, there is no need for it, but getting the velocity up would help.

You sneaky bastard! :fawk: :bowrofl: :bowrofl: :bowrofl:

I'm not sure I've ever seen anyone post back-to-back numbers for hand porting on a BP. Hopefully you can get your base together before you rip through all the ports. :bigtu:

Thanks. I'm not falling into a rabbit hole, I've done that. I'm trying to get a Miata back on the road and it looks like I'm going the junkyard route.

The tool used to create valve seat has a big guide that creates the big step in the bowl. Ever seen a K20 port. That is how a company that obsesses over specific engine output more that how it handles, does their heads. FWD + Superbike ports or race car suspension design + head design that needs to wear a helmet.

When I see an OEM Honda head, I cry a little.

They want to crank them out fast in production. The car makers will do what they can to shave .01 per unit, so another step in maching, all adds to the cost, in labor and tooling.

I doubt when the engineers that designed the head for the BP, even considered bolting a turbo to it, it was all about MPG.


I doubt that, But I have another head on the shelf I will try to flow befor I set it up on the porting table.


Thats understandable, at a min, have the basic checks done on the head before you bolt it into place.

+100

Well, my machinist won't buy a tap to make sure the threads are good on my spark-plug hole so he expect me to pay money for the rebuild (if the valves are bent), then diagnose the spark plug hole problem. I can't dump $700+ into new valvetrain into a bad core, so I'm not really sure what to do at this point. Maybe time to give up.

Exhaust side
 

Looking down the exhaust runner, stock
Working the roof and divider of the runner.

Keep in mind the head is upside down.

https://www.miataturbo.net/attachmen...ine=1356732320


Getting it rough in, and thinning the divider a little bit.

https://www.miataturbo.net/attachmen...ine=1356732320

I can only port for about an hour or so at a time, keeping controll of the grinder is key.

Lets say I wanted to mess around with a trash head, what does a decent set of bits like these cost? Where to buy?

That dosen't sound right, I could understand $40-50 to teardown and inspect the head and estimate write up, if you decided not to go through with the rebuild, or if the casting is beyond repair.

But not wanting to spend $25-$30 on a spark plug thread chaser????
Last tool on right
https://www.miataturbo.net/attachmen...ine=1356735893

$700? That must be a full ST valve and spring kit w/Ti Retainers.

The machinist you are using must be too busy, or not intrested in doing your head build.

Oh decent carbide burrs will run from $30 -$100+ each, depending on make, shape, length.

Then a porting kit with mandral and cartarage rolls is another $30-$60

On porting this head I have used 3 diffrent burrs.

Exhaust bowls roughed in

https://www.miataturbo.net/attachmen...ine=1356817068Now the intake and exhaust runners and bowls are all roughed in.

Looks a bit ugly at this point.
https://www.miataturbo.net/attachmen...ine=1356743871

Time to pretty it up a bit.
Getting the roof and divider smoothed out.
https://www.miataturbo.net/attachmen...ine=1356743871

Now the bowl blended into the runner.
https://www.miataturbo.net/attachmen...ine=1356743871

If I can find a cheap head, I may give this a go myself. I have some junk valves to work on the chamber too.

I have no pictures from my portwork, but some flow numbers
No real need to work the exhaust much for a NA build, but going to three angle grind removed a vortex on the exhaust side and increased flow somewhat (words from my builder, I'm just learning to appreciate the knowledge).