BP Head Porting

[ben]

So, I picked up a BP head from a 91LX a few weeks ago to get a few things going: (1) obtain an extra exhaust cam for the exhintake conversion and (2) get a head rebuilt / ported for the eventual BP swap into my tired DX chassis. I've decided to go NA for a while, just because I can build it slower (cash-flow wise). So the plan for the motor is:

exhintake, with modified stock timing gear (save cash on adjustable)
ported head & matched intake
required overbore on block (0.020?)
Genie header + cat back
RX7 VAF & cone filter
Possibly mill head and / or block for compression
2001 Miata pistons

Since the wife was out of town, the kitchen counter was chosen for head disassembly & cleaning. Spread the newspaper, tub of degreaser in the sink, onward. The cam bearings all looked okay, the ones down by the drive end seemed a bit more "polished" than the others. Some showed almost no wear. Cleaned them all & put them in labeled baggies with their hardware.

The hydraulic lifters were about the same. Mostly looked new, with a little extra polish in a few places. These did NOT go in the degreaser soup, they were just hand-wiped down, verified that the internal springs still worked, and individually bagged & labeled. They will get cleaned & manually pumped (have fun with that) in 10-weight oil before they go back in the motor.

Started to take out the valves, when I discovered that my spring compressor that worked on my Buell will NOT work on the BP head. After some gymnastics with an 18mm socket, I got the retainers out on one intake valve, and removed the valve. It looked like a 100,000 mile valve; lots of carbon on the valve both back & front. Chambers are all black.

So, after the valve was out I started looking at the ports. The short side radius looks like it could be blended, and maybe some other light blending around the rest of the seat looks okay too. The ports are filthy, so they'll get polished up too.

Looking at the combustion chambers, I think I see some flow waiting to be had. The sides of the chamber are right next to the intake valve, the walls have GOT to be shrouding the valves. It looks like cutting those areas back will allow for better flow into the chambers. I guess that means I'll have to cc the chambers to get them all the same, that should be fun. I'm hoping to get an ending compression ratio about 10.5:1 or so.

Has anyone tried that mod to the heads?

[kozzman555]

im actually gonna be getting a bench flow tester and all the bores and hones i need, as well as the mic's needed for measuring everything. with some practice on other heads, ill probably do a few PnP's, valve jobs and port matching and sell them

[Shades]

Porting takes a long long long long long time... trust me, I just finished my head for my build, and now I'm polishing them to look like glass which is also gonna take a long time, but I don't think as long as the porting will. I cleaned up all the casting slag in the ports and when I port matched it I also too quite a lot of material out... all in all, I hope these gains are worth the relentless hours I put into it.

[Jho]

While you have your lifters out, you should do this to them:

http://www.wihandyman.com/forum/showthread.php?t=11841

Good luck with your project. Keep us posted on the progress.

[ben]

On we go

Thanks for the tips about cleaning up the HLA's! Most of them moved when I took them out; I was just going to pump them with 10-weight a bunch of times to clean them out. Thanks to your thread, it looks like cleaning them outright isn't too much of a hassle.

So, another weekend, so I spent the night on the floor watching a rerun of the Brazilian F1 race & stripping the valves from the BP head. (I have an understanding wife. Tolerant, but understanding...)

Notes:

1. There is a tip over at miata.net (http://www.miata.net/hakuna/port2.html) about fabricating a valve keeper removal tool from a piece of 3/4" pipe. So, I made my own to get the valves out. Thanks!
2. There is a whole thread at miata.net about the exhintake as done by a guy who did NOT buy adjustable cam gears, but had a stocker modified. My new hero, as I've ready access to a machine shop.
3. The intake valve guides look like easy money. They are already recessed into the port to the point where the trailing edge is almost buried into the port ceiling. The other side (upstream) protrudes from the port maybe 80-thou. I'm really thinking about just grinding them flush during the porting process....
4. The exhaust guides look the same way. Not as willing to cut the valve guide overall, since it helps to get heat away from the valve. Might try cutting that flush too, we'll see once the die grinder gets started.
5. The exhaust ports were sloppier than the intakes, I expect that bowl blending will get me more on the exhaust side.
6. Need gaskets. There were big buildup crud ridges around the intake port's connection to the intake manifold. I suppose I'll get a gasket, drop it over the bolts, and mark the gasket outlines on the head. We'll grind & taper from there.

I've also recieved my B-coded RX-7 VAF from a board member (thanks!!), and it is duly boxed next to the valves on a labeled shelf in the basement. Not really sure I want to go through the effort of installing the VAF on the SOHC motor. Doesn't seem like I'd see a gain, but its one step further down the road for the DOHC conversion.

I've finally received my camber plates from Corksport, so we'll try to get those installed tomorrow. ZX2 struts already installed (impatient, I know) using ZX2 bearings & mounts I got from a local U-pull-it junkyard for $10.

Add me to the list of kiss-asses on the site.

What a resource this site has been. From the RX-7 VAF, the exhintake mods, the turbo information, the ZX2 suspension upgrades, everything has been great. Being a cheapskate myself I really appreciate the creative methods that various board members have developed to upgrade their rides.

Someday I hope to beat naprotejay's dyno numbers!

Onward & upward, the head gets scrubbed tomorrow. Then the grinder comes out...

[gtx510]

put a 6" extension on a 17-18mm long socket and put that over the spring retainer. Then hit the extension with a hammer. If you get it right both locks will pop out and the valve will drop.

only polish the exhaust ports. or get them coated and don't bother polishing.
on a mild engine I'd most play with the valve bowls/pockets, smoothing the shortside radius, unshrouding the valves, and gently shaping the port divider but not knife-edging it. Work on all the ports at once to ensure that you are making identical cuts.
Flowbenches work best with a cylinder replicated underneath, and a clay bell-mouth entry to the ports or the manifolds on the head. You could make one with a DIY manometer (or a vacuum gauge) and a vacuum cleaner.

http://www.theoldone.com/ Endyn's sight is kinda cool.

http://www.theoldone.com/articles/

http://www.theoldone.com/components/cylinderheads/

http://www.theoldone.com/components/...ead_modifi.htm if only you could make the chambers look like this.

[therieldeal]

glad to hear you recieved your vaf , and it sounds like a fun project you have here. good luck!

-jon

[FE3-323]

Id like to bring my head to endyn & see what they can do to it.
walk up to the desk & say
here, I've got a spare head & my good head, tell them to research with the spare head as much as they want & let me know what can be improoved in my other head

[gtx510]

I've thought of doing the same thing with a couple spare B6T heads that I have.