head porting dohc bp,info, pics,ect.

[ryan1]

im going to be rebuilding a dohc bp head for a 1 of my boosted bp cars, it will be a budget build were i will just lap the valves,clean up parts, and stem seals..

so i was thinking a porting it a little or i might just clean up the rough castings,ect.

i know head porting is a weird deal sometimes on weather its worth it or not, i have ported a few ford 302 heads, but there was documented info about it and a rough guide on what to do....

so anyone have any info,links,pics pretaining to porting a dohc bp head?

[Mazda_Powered]

What I've done in the past is use gaskets as the template for port work. You line the gasket up to both the head and corresponding manifold then trace out the overlap with a permanent marker so you can later etch the design in with a dremel/rotary tool. Then simply use that port as a guide!

For getting deep inside to open it up, you can use a caliper system to measure the width of the ports and port it out til you get it within spec (ie. 10-15% larger than stock).

For cleaning up the combustion chamber, you can use this link, it'll tell you about figuring out the volume, and how to keep it consistent.

http://www.merkurxr4ti.com/chambervolume.html

Also normally the exhaust ports will be mirror finish, and the intake side will more porous than said exhaust ports.

[FE3-323]

search for threads by me in the photo-video section............. you'll see some pictures/information

enlarging the ports isn't really where much of any gain comes from with these heads. cleaning them up properly & fixing the short side radius of the exhaust ports is where you'll see gains.

[ryan1]

search for threads by me in the photo-video section............. you'll see some pictures/information

enlarging the ports isn't really where much of any gain comes from with these heads. cleaning them up properly & fixing the short side radius of the exhaust ports is where you'll see gains.

this one???

http://www.wihandyman.com/forum/showthread.php?t=42813

[ryan1]

here are some other ones i found.....

http://grassrootsmotorsports.com/forum/grm/miata-head-porting-thread/27115/page1/

http://www.miataturbo.net/showthread.php?t=40672

[ryan1]

what makes the BP4W head better than the bp05 head anyway, never really looked into it, but iirc the ports were a little different, maybe i can copy them tot he bp05 head ???

[FE3-323]

if your going for a better head........ get the VVT head or don't really bother.

the BP4W head has better port angle which helps CFM/velocity.
took them until 99 to re-mimic what they built the FE3 head as....... sad

[Mazda_Powered]

Vvt bp4w ftw

[heyoldguy2002]

the above links are about as bp specific as I found...and my pics are about the same.

I used this touch up kit http://www.cylinderheadsupply.com/poandpokitto.html but I would recommed a larger kit from them. Use compressed air and die grinder.

some of the domestic 2 valve techniques are useful...but very little is out there about 4 valvers...many sites brag about honda heads and methods of porting. http://www.theoldone.com/ much info here

I unshrouded the valves, cc'd and polished chambers (polished to reduce carbon build up and hot spots), bowls opened up 3%, ports opened 4% intake/ 5% exh. Ported gtx manifold, ported bp intake, cut intake mod and opened up plenums cross-over (VICS assistance). I kept a step between intake and head to help prevent reversion, and same on exh side (Gude likes to call it "step technology"...its just an old procedure that comes factory on these Mazda bp's) My goal was velocity...just a mild clean-up. Polished exh ports, and 80 grit on intakes...boundary layer is important on wet flow intakes to reduce fuel / air separation).

Yes, the short side radius / throats must have smooth transitions to the seat. My Manley Pro-flow valves should help low lift flow as well.

One special note: the intake gasket and exh gaskets hang down into the passages from the port roof...about 1.5mm. That is stock noticed upon engine disassembly...come on Mazda, thats pathetic. Simply enlarging the gasket opening ought to be worth better flow...never mind the above mentioned work.

I must figure out uploading of pics...but it would only be bragging. My machinist also added his $.02...said the work was good...but also said there is little improvement to be had as the 4 valve heads come pretty good and large from factory, compared to domestic V8's.

I too know the Ford 302...the BP ports are better by far.

[ryan1]

here is a nother one i found....

http://www.miata.net/hakuna/port2.html

[heyoldguy2002]

hakuna was my inspiration

I also got a valve grind...15, 45, 75 degrees...as opposed to the usual 15, 45, 60...as a miata head showed good flow rates with 75 at the bowl. In fact my machinist mentioned that the stock angle seem to be 75...go figure, Mazda engineers can be great.

http://users.erols.com/srweiss/index.html this site has everything in it...flow rates for Mazda heads in there.

I have not had my work flowed or dyno'd...must assemble and install. Will have full on turbo BP by september.

[heyoldguy2002]

my head work

would love to do it again...will do a before and after flow test on my other one when its done; just for curiosity.

I hope this helps others out there.

I have been thinking of providing this as a service business.

[mx-3_4evr]

^ ****ing nice! Make sure that the cast markings are completely gone

[Mazda_Powered]

that's looking real nice!

[heyoldguy2002]

^ ****ing nice! Make sure that the cast markings are completely gone

thought about enlarging to remove the port parting lines, but decided that 3mm increase in size all around had already been achieved, did not want to alter port shape, and seeing that the intake manifold is already much smaller i did not want to create a large dead zone / mismatch. The goal was really just a clean-up and mild port...to maintain velocity especially at low cam lifts. Our cams are mild...a bigger port may just be overkill.

Although, carving the port all the way may be very sexy looking. (Its my anniversary today...I think my mind is elsewhere) It was very hard to finally just stop the work...all literature warns not to get carried away...I am a perfectionist and prone to ruining things due to overkill. (Kinda like all these posts...but I am trying to pay it forward for once).

I am done:

22 hrs into the ports alone is reasonable, the chambers took way too much extra time (cc and equalizing is all trial / estimate work until all spec'd out to 52 cc), polishing the chambers is just showing off (had compounds and buffs already, so why not) and not worth power. To keep all ports in proportion and of equal size to each other was the ultimate challenge...fun really (Am I sick?)

Thanks for the compliment.
Pay your head porter handsomely...its tough work.