benefit of porting

[windy1]

what benefits have u,gotten from porting/milling a festiva head. were any improvements noticable? any tips u all wish to share about porting

[htchbck]

Search the username "zanzer" on here for head porting. He did a great thread with lots of pics on the B3, including one with a junk head cut in half to show a good cross section!

[link5186]

Zanzer's thread is here: http://www.fordfestiva.com/forums/sh...ad.php?t=36336

I did a fairly mild port job when I rebuilt the B6 I swapped in. I can't give you much as far as before and after goes, but I have no complaints about how it turned out. I rounded down the exhaust ports where that steep angle is and smoothed out the ridges on both sides followed by some blending. I didn't enlarge any of the ports, just smoothed out the rough spots. I did all my port work without removing the valve seats and tried to be as careful as possible so not to damage the seats. I know you're looking for fuel efficiency in your build. My suggestion there would be to concentrate on the exhaust side and leave the intake side as is.

Tips? Take your time. The B6 port job was the first I ever did. I took it slow and was pretty nervous at first. Get a feel for how your grinder acts on the aluminum and don't let it get away from you. Looking back, I probably should have taken more off of the exhaust ridge, but even just smoothing it down some is an improvement.

Read, study the pictures, then go at it.

[windy1]

thanks. wasnt planning to mess with intake,other than to match the gasket. same for exhaust. dont want to take much off ,afraid ill hit water jacket.

[Christ]

There's a good chunk of the exhaust tract that chokes down flow in the head where the port floor meshes (not very well) with the port off the valve. If you can clean that area up and semi-polish the port, you'll be a lot better off than any stock B3 as far as flow is concerned.

Try to keep all 4 ports even.

[windy1]

ive had feedback from people,after they did a good port job. they said they couldnt get any,or only very little power,because intake manifold was so small. better flo cant go any faster,if manifold has small ports. when mazda,made this engine,it didnt miss a thing

[blkfordsedan]

Actually, small ports provide a higher velocity and are exactly what you want on a street engine. When it comes to flow, its all about shape and notphysical size. Christ is exactly right about the transition area between the port walls and valve pockets. There is a major mismatch there...on both intake and exhaust. Smooth and blend this out and you'll get the most benefit for the least effort. Personally, due to the port design and shape, I don't think the sharp angle on the short turn radius of the exhast port is as big of an issue as it appears. I would just round it off and not try to completely reshape the port floor.

[Christ]

There's simply not enough flow through the head to necessitate a major reshaping. Opening up the port slows down port velocity because there isn't enough fluid mass to fill the port and keep the velocity up unless you also work the intake.

Focus on the casting marks and sharp edges.

[DriverOne]

What benefit would a match provide? Could you see an MPG boost, or a quicker idle to rev response time?

[Christ]

What benefit would a match provide? Could you see an MPG boost, or a quicker idle to rev response time?

To what sort of "match" do you refer?

[blkfordsedan]

Reshaping the port and even adding volume in some specific areas can be quite beneficial. The thing is, without a flowbench and some testing, its pretty hard to determine what changes have what effect, and at what valve lift. With fluid dynamics, things don't always work out as perception would have it.
The general accepted rule is that any casting flash, sharp edges or anything that may create turbulance will improve flow if eliminated. Anything more should be subject to flow testing to be certain. The point of gasket matching the intake and head is simply to reduce turbulance as the waves traverse back and forth between the intake plenum and valve.

[windy1]

i want to give u,credit, without a flo bench after major porting u,ll never know. these are my sentiments as well. mazda hasnt missed any thing. ill follow your advice,thanks again

[DriverOne]

To what sort of "match" do you refer?

Christ is exactly right about the transition area between the port walls and valve pockets. There is a major mismatch there...on both intake and exhaust.

Like that.

[Christ]

Like that.

Then yeah, that could be beneficial, but it's not something you can do just by looking at it unless you've already flowbenched one with similar mods and have the experience.

The idea of opening up flow in the head for efficiency is just to keep velocity high at low flow rates, so removing restrictions.

You can move the BSFC into a more desirable RPM range via head porting and machining, but for the average DIY'er, it's just "cleaning up" and nothing more. Port matching, removing casting flash and marks, etc.

[windy1]

thats all i evr do with any head. unless i had a flo bench,and a teacher,looking over my shoulder. thanks CHRIST and all u,other dudes