is it just me or is the divider thing not supposed to be knife edged like that?

I thought I read somewhere that you want it to have a similar shape as an airplane wing, and not knife edged like /\

 

I don't think he's done just yet.

I'll wait right here for more pics to come by.

 

I wonder....


Yes I read it too



What I find intresting, is no one has asked about the valve guides.....

 

It's "obvious"
You have remove them for the port work and plan to put unmodified (old/new) guides back in there.
The trade-off of poorer valve guidance is not worth it for the slightly increased flow.

 

+1 That kills valve guides.

 

MT.net head porting for dummies?

Sorry for the threadjack but,
Would something like this kit from Eastwood get it done for a DIYer?

 

can you please flow a stock port on that head, i never got to do it on my head and would like to know gains over factory, i would also like to compare my flow number vs yours, nice write up and looks real nice. i know what you mean about flow bench bores and actuators. our superflow was set up for v8's i had to make a dohc actuator and a 85mm bore stand

 

True true.. And porting the intake bowls is a ton simpler with the guides out if the way.


Thats a decent base kit with the burrs that are in it, you will want to order some more sand paper rolls, 10 is just not enough

Ill start getting some flow data once I get a stand and actuator built.
I have started to gather some of the parts for the stand.
Superflow is just a bit expensive on the stands they sell.

 

dont hate.

 

You may have figured out, I don't have much hate in me. But yeah, removing the area of the port roof that supports the valve guide then cutting a significant portion of the guide away results in rapid valve guide wear. Not worth the flow gain IMO. I have seen over 230cfm at around .370 (BP6D intake) @ 28 hg on a skillfully ported head. That's about a 12% gain with stock cams. One can have their cake and eat it too.

Miata heads always die from valve seat wear and the OEM springs allow float at modest RPM. Why speed that process up? It makes as much sense as razor thin zillion angle valve seats that flow like mad and are toast in 20 hours.

I might cut away the valve guides for a Nationals grenade motor but not on an HPDE or DD build.

 

My head still has depressions where it ate a screw in the squish area on #4.

 

singh groves?

 

exactly!

 

Braineack... The port work looks good, and the guides touched at the end will have little effect on anything.

Emilio... I will agree, cutting the guides down is not the best thing to do on most heads.It does kill the support of the valve stem and wear will occure faster.

Most all the time I have seen excessive seat wear on a sinter metal or powder metal seat insert is from a valve job that did not control seat run out, and the valve had to pound the run out from the seat.

 

Quick question: removing/reinstalling the valve guides - is it just a matter of pressing or pushing or hammering them in/out? Or do you have to do something fancy like freeze/heat up the area like I've seen on some youtube videos of fancy shmancy engines?

 

18psi.. it really comes down to the head.
But thos is the most common method.

https://www.miataturbo.net/engine-pe...er-head-64857/

Some times a guide will not just press out, then heat is used.
If heat does not work, then the guide will be "shelled out" That is a PITA, the guide is reamed paper thin, then chipped out.

 

got it. thanks sir

 

BP combustion chamber porting.






The stock chamber.
Blue lay out dye has been applied.
A used HG is the template.


The main reason to do this is to remove the factory casting imperfections, along with removing potential hot spots.


Bevel the sharp edges.





Now the head is ready to be cleaned, and have the guides installed, and the valve job done.

 

HOLT ****! That looks nice!

 

Is there a better than stock option for valve guides?

It seems head porting on BP motors doesn't make much more power. Is it worth the effort to take the guides out, port it, new (better?) guides, and reassemble. Plus the head rebuild while you're there. How much is 12% more flow help in a turbo car? Not doubting it wouldn't, but how much.