head porting

[custom]

right now im porting my a20 head for the first time. how much HP gain is expected? i plan on puting it on a dyno but, i would like to wait on getting the cams redone.

[shepherd79]

well if the porting is done properly you can gain very nice HP, but if proper porting is done wrong, you can actually loose torque and power.

[custom]

how can you go wrong with porting? as long as the ports are broaden and smooth their should'nt be no problems right? i heard if you take too much from the bottom you could lose power at the bottom but gain at the topend only

[BITESIZE]

If the manifold doesn't match the head dead on, that causes resistence which will make you lose power? Air has to flow perfectly to see gains in power? I'm not sure but makes sense.

[2oodoor]

must be very precise and carefull doing that, Honda was pretty precise in making the casting so that it heats up and cools down at an acceptable rate so as to remain durable. Cutting too much out for example between water jacket and combustion chamber could create a problem with the piece retaining the proper shape and diminsions.
Same theory applys if you are boosting, you have to make sure the tempurature cools down to point where it is safe to shut off the engine.

[rjudgey]

try searching for numerous posts written by me not in the mood to write yet another 1000 word guide on head work. Also check out my cardomain and myspace pages too.

BTW might be joing the 3G club soon how about a Aerodeck in polar white with only 38k miles only downside to this immaculate piece of art is it's an Auto!! and has a A20 inside!! But with a spare B20A and Box at the ready could get very interesting ;0))

[2ndGenGuy]

try searching for numerous posts written by me not in the mood to write yet another 1000 word guide on head work. Also check out my cardomain and myspace pages too.
BTW might be joing the 3G club soon how about a Aerodeck in polar white with only 38k miles only downside to this immaculate piece of art is it's an Auto!! and has a A20 inside!! But with a spare B20A and Box at the ready could get very interesting ;0))

Do you have links to your cardomain and myspace pages? I've been dying to check your stuff out, but there's no info in your profile.

[rjudgey]

http://www.cardomain.com/ride/281725

http://profile.myspace.com/rjudgey

[cygnus x-1]

I saved the link to Rich's guide to head porting over at PP.

http://www.preludepower.com/forums/s...=valve+springs

Basically you want to create smooth unrestricted flow into the cylinders. But you don't want the ports so big that you reduce the velocity of the air. High air velocity gives you torque and throttle response by creating sort of a ram air effect. This is why small diameter long intake runners are good for low RPM torque. They're bad for high RPM power though because the small diameter restricts flow. Large short runners are good for high RPM power because the flow is unrestricted, but at low RPMs the velocity will be low, and torque and throttle response will suffer.

The A20 ports are already pretty big so they don't need to be any bigger. Mostly you just want to smooth over any rough areas or sharp edges. Also try to match the intake manifold to the intake ports on the head by removing as little material as possible.

And really the biggest gains are going to be had by just getting a good quality 3 angle valve job. Also tell the shop that you want a performance grind and not just a factory type job. A performance grind will have narrower valve seats and will flow better.

You can also follow along as I did my headwork (and full engine rebuild) here:

http://www.preludepower.com/forums/s...d.php?t=238337

I did the headwork somewhere in the middle of the thread so you'll have to troll through it. But much of it was done under Rich's guidance so there are lots of little bits of wisdom scattered throughout.

Good luck!

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